Lidé
Ing. Jakub Cikhardt, Ph.D.
Všechny publikace
Characterization of bright betatron radiation generated by direct laser acceleration of electrons in plasma of near critical density
- Autoři: Ing. Jakub Cikhardt, Ph.D., Gyrdymov, M., Zähter, S., Tavana, P., Günther, M.M., Bukharskii, N., Borisenko, N., Jacoby, J., Shen, X.F., Pukhov, A., Andreev, N.E., Rosmej, O.N.
- Publikace: Matter and Radiation at Extremes. 2024, 9(2), 1-10. ISSN 2468-080X.
- Rok: 2024
- DOI: 10.1063/5.0181119
- Odkaz: https://doi.org/10.1063/5.0181119
- Pracoviště: Katedra fyziky
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Anotace:
Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativistic laser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In an experiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 1019 W/cm2 laser intensity. The spectrum of directed x-rays in the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0° and 10° to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 1013 photons/sr with energies >5 keV measured at 0° to the laser axis and a brilliance of 1021 photons s−1 mm−2 mrad−2 (0.1%BW)−1. The angular distribution of the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emission time, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laser facilities.
Comparison of density profiles measured via laser interferometry with MHD simulations during shock wave reflection on mega-ampere dense plasma focus
- Autoři: Ing. Jakub Malíř, prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Paduch, M.
- Publikace: PHYSICS OF PLASMAS. 2024, 31(4), 1-13. ISSN 1070-664X.
- Rok: 2024
- DOI: 10.1063/5.0193268
- Odkaz: https://doi.org/10.1063/5.0193268
- Pracoviště: Katedra fyziky
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Anotace:
The analysis of Z-pinch implosion dynamics plays one of the most important roles in the study of pulsed power discharges. At the same time, it is difficult to determine the density distribution together with the current density (current coupling to the imploding layer) to provide more detailed information about the dynamics. Numerical simulations can now provide high-resolution results that are almost unattainable in experiments. The challenge, however, is to obtain reliable results that are close enough to the experimental data to describe individual physical phenomena. In this paper, we show that it is possible to use a combination of experimental data and magnetohydrodynamic (MHD) simulations to verify and identify the physical processes during the stagnation of a Z-pinch. We focus on the analysis of the density profile from experimental data of the mega-ampere plasma focus PF-1000 and its reconstruction using an extended MHD code. Thanks to multi-frame interferometry, we recorded a total of 29 interferometric images of two shots, each in a 200 ns time window around the pinch phase. We were then able to obtain density profiles and observe the reflection of the shock wave from the axis. By the appropriate choice of initial conditions and boundary values in the simulation, we were able to obtain reasonable agreement with the experimental values. We also evaluated the possible shortcomings of the 1D simulation, such as mass loss and current flow at the periphery.
Evolution of filament-like compact structures in small 3 kJ dense plasma focus discharges
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Marciniak, L., Sadowski, M.J., Paduch, M., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., Kravárik, J., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2024, 31(8), 1-11. ISSN 1070-664X.
- Rok: 2024
- DOI: 10.1063/5.0187304
- Odkaz: https://doi.org/10.1063/5.0187304
- Pracoviště: Katedra fyziky
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Anotace:
This paper presents the filamentary structure of the pinched column in a smaller plasma focus device filled with deuterium. The deflections were observed using schlieren and differential interferometry techniques. The observed filaments have a transverse diameter of 40-200 mu m, which could be interpreted based on the electric current hypothesis as local concentrations of electric current. The evolution of filaments was compared with global structures recorded by extra ultraviolet frames. These results provide a basis for considering the possibility of a filamentary composition of the poloidal current in compact structures. The model of filaments with a helical shape of electrical current may be able to explain the central narrow and dense cord in the axis of the column, the different lifetimes of the structures, and the submillimeter sources of fast electrons and ions.
High-brightness betatron emission from the interaction of a sub picosecond laser pulse with pre-ionized low-density polymer foam for ICF research
- Autoři: Gyrdymov, M., Ing. Jakub Cikhardt, Ph.D., Tavana, P., Borisenko, N.G., Guskov, S.Yu., Yakhin, R.A., Vegunova, G.A., Wei, W., Ren, J., Zhao, Y., Hoffmann, D.H.H., Deng, Z., Zhou, W., Cheng, R., Yang, J., Ing. Jan Novotný,
- Publikace: Scientific Reports. 2024, 14(1), 1-14. ISSN 2045-2322.
- Rok: 2024
- DOI: 10.1038/s41598-024-65490-7
- Odkaz: https://doi.org/10.1038/s41598-024-65490-7
- Pracoviště: Katedra fyziky
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Anotace:
Direct laser acceleration (DLA) of electrons in plasmas of near-critical density (NCD) is a very advancing platform for high-energy PW-class lasers of moderate relativistic intensity supporting Inertial Confinement Fusion research. Experiments conducted at the PHELIX sub-PW Nd:glass laser demonstrated application-promising characteristics of DLA-based radiation and particle sources, such as ultra-high number, high directionality and high conversion efficiency. In this context, the bright synchrotron-like (betatron) radiation of DLA electrons, which arises from the interaction of a sub-ps PHELIX laser pulse with an intensity of 1019 W/cm2 with pre-ionized low-density polymer foam, was studied. The experimental results show that the betatron radiation produced by DLA electrons in NCD plasma is well directed with a half-angle of 100-200 mrad, yielding (3.4 +/- 0.4)1010 photons/keV/sr at 10 keV photon energy. The experimental photon fluence and the brilliance agree well with the particle-in-cell simulations. These results pave the way for innovative applications of the DLA regime using low-density pre-ionized foams in high energy density research.
High-repetition-rate source of nanosecond duration kA-current pulses driven by relativistic laser pulses
- Autoři: Ehret, M., Ing. Jakub Cikhardt, Ph.D., Bradford, P.W., Vladisavlevici, I.M., Burian, T., de Luis, D., Henares, J.L., Martín, R.H., Apiñaniz, J.I., Lera, R., Pérez-Hernández, J.A., Santos, J.J., Gatii, G.
- Publikace: High Power Laser Science and Engineering. 2024, 12 1-10. ISSN 2052-3289.
- Rok: 2024
- DOI: 10.1017/hpl.2024.14
- Odkaz: https://doi.org/10.1017/hpl.2024.14
- Pracoviště: Katedra fyziky
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Anotace:
We report the first high-repetition-rate generation and simultaneous characterization of nanosecond-scale return currents of kA-magnitude issued by the polarization of a target irradiated with a PW-class high-repetition-rate titanium:sapphire laser system at relativistic intensities. We present experimental results obtained with the VEGA-3 laser at intensities from $5\times {10}<^>{18}$ to $1.3\times {10}<^>{20}$ W cm ${}<^>{-2}$ . A non-invasive inductive return-current monitor is adopted to measure the derivative of return currents of the order of kA ns ${}<^>{-1}$ and analysis methodology is developed to derive return currents. We compare the current for copper, aluminium and Kapton targets at different laser energies. The data show the stable production of current peaks and clear prospects for the tailoring of the pulse shape, which is promising for future applications in high-energy-density science, for example, electromagnetic interference stress tests, high-voltage pulse response measurements and charged particle beam lensing. We compare the target discharge of the order of hundreds of nC with theoretical predictions and a good agreement is found.
Hot electron emission characteristics from thin metal foil targets irradiated by terawatt laser
- Autoři: Sushil Kumar Singh, Ph.D., Krupka, M., Krása, J., Istokskaia, V., Dostal, J., Dudzak, R., Pisarczyk, T., Ing. Jakub Cikhardt, Ph.D., Shubham, A., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Giuffrida, L., Chodukowski, T., Rusiniak, Z., Burian, T., Margarone, D., Krůs, M., Juha, L.
- Publikace: Laser and Particle Beams. 2024, 42 1-9. ISSN 0263-0346.
- Rok: 2024
- DOI: 10.1017/lpb.2023.2
- Odkaz: https://doi.org/10.1017/lpb.2023.2
- Pracoviště: Katedra fyziky
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Anotace:
The interaction of focused high power laser beam with solid targets leads to acceleration of charged particles among other by non-linear effects in the plasma. In this experiment, the hot electrons are characterized from the interaction of sub-nanosecond and kilo-joule class laser pulse with thin metal foil targets (Cu, Ta, Ti, Sn, Pb). The energy distribution functions of electrons were measured by angularly resolved multichannel electron spectrometer. The hot electron temperatures were observed in range from 30 to 80 keV for laser intensities between 10^15 and 3x10^16 Wcm^-2. The measured energy distribution and electron temperature were compared with published results and known scaling laws at higher laser intensities. For foil targets of different materials, the temperature and flux of hot electrons were scaled with target thickness in the range of 1-100 um from low Z to high Z materials where Z is the atomic number. The profile of conversion efficiency from laser energy to hot electrons is discussed in the energy range from 100 to 600 J. For the given laser and target parameters, the nonlinear behaviour of conversion efficiency and relevant physics are also described in detail.
Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser
- Autoři: Krása, J., Burian, T., Hájková, V., Chalupský, J., Jelínek, Š., Frantálová, K., Krupka, M., Kuglerová, Z., Sushil Kumar Singh, Ph.D., Vozda, V., Vyšín, L., Ing. Jakub Cikhardt, Ph.D., Falk, K., Juha, L.
- Publikace: Matter and Radiation at Extremes. 2024, 9(1), ISSN 2468-080X.
- Rok: 2024
- DOI: 10.1063/5.0157781
- Odkaz: https://doi.org/10.1063/5.0157781
- Pracoviště: Katedra fyziky
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Anotace:
We report on an experiment performed at the FLASH2 free-electron laser (FEL) aimed at producing warm dense matter via soft x-ray isochoric heating. In the experiment, we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell-Boltzmann velocity distribution model. We find that most emitted ions are thermal, but that some impurities chemisorbed on the target surface, such as protons, are accelerated by the electrostatic field created in the plasma by escaped electrons. The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures. We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.
Self-driven ion deflectometry measurements using MeV fusion-driven protons and accelerated deuterons in the deuterated hybrid x-pinch on the MAIZE LTD generator
- Autoři: Ing. Vojtěch Munzar, Ph.D., Dowhan, G., prof. Ing. Daniel Klír, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Chen, J., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Bc. Vojtěch Juráš, Jordan, N., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Malíř, Tafoya, L., Turek, K., McBride, R.
- Publikace: Plasma Physics and Controlled Fusion. 2024, 66(7), 1-14. ISSN 0741-3335.
- Rok: 2024
- DOI: 10.1088/1361-6587/ad5104
- Odkaz: https://doi.org/10.1088/1361-6587/ad5104
- Pracoviště: Katedra fyziky
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Anotace:
We report on the results of point-projection ion deflectometry measurements from a mid-size university z-pinch experiment. A 1 MA 8 kJ LTD generator at the University of Michigan (called MAIZE) drove a hybrid x-pinch (HXP) with a deuterated polyethylene fiber load to produce a point-like source of MeV ions for backlighting. In these experiments, 2.7 MeV protons were generated by DD beam-target fusion reactions. Due to the kinematics of beam-target fusion, the proton energies were down-shifted from the more standard 3.02 MeV proton energy that is released from the center-of-mass rest frame of a DD reaction. In addition to the 2.7 MeV protons, strongly anisotropic beams of 3 MeV accelerated deuterons were detected by ion diagnostics placed at a radial distance of 90 mm from the x-pinch. Numerical reconstruction of experimental data generated by deflected hydrogen ion trajectories evaluated the total current in the vacuum load region. Numerical ion-tracking simulations show that accelerated deuteron beams exited the ion source region at large angles with respect to the pinch current direction.
Effect of anode shape on neutron and x-ray emission in dense plasma focus
- Autoři: Ing. Jan Novotný, Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2023, 30(8), 082702-1-082702-10. ISSN 1089-7674.
- Rok: 2023
- DOI: 10.1063/5.0153177
- Odkaz: https://doi.org/10.1063/5.0153177
- Pracoviště: Katedra fyziky
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Anotace:
The neutron and x-ray production is investigated in various pulse-power devices for a deeper understanding of the ion and electron acceleration mechanisms and the application of pulsed neutron sources. We present the extensive results from an anode shape experiment carried out on the PFZ-200 plasma focus device. The various shapes of anodes were tested, including cylinders, tapers, or rounded tips. The experimental shots with a peak current above 200 kA were performed in pure deuterium working gas at 280–600 Pa pressure to obtain maximal neutron yield for each anode shape. The average neutron yields are in the range of (1–2) ×108 neutrons/shot. Outstanding findings about x-ray emission were obtained with the group of tapered anode tips. Using the scintillation detectors shielded by 5 cm thick lead bricks, we obtained the hard x-ray signals with photons exceeding 600 keV energy. Such relatively high x-ray energy indicates the optimized conditions for electron and ion acceleration. At the same time, the individual shots have been well reproducible. Therefore, we were able to study plasma dynamics with the schlieren images taken at different times at different shots.
Filamentary-like structures of plasma in a small 3-kJ dense plasma-focus discharge in pure deuterium
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Marciniak, L., Sadowski, M.J., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2023, 30(7), 1-10. ISSN 1070-664X.
- Rok: 2023
- DOI: 10.1063/5.0148405
- Odkaz: https://doi.org/10.1063/5.0148405
- Pracoviště: Katedra fyziky
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Anotace:
Filament-like structures were observed during discharges in a small 3-kJ plasma focus device operated with pure deuterium. These structures were recorded by means of two different laser diagnostic techniques: a schlieren system and a differential laser interferometry. They present the novel fine-scale (submillimeter) plasma structures recorded during the radial implosion, at the pinch stagnation, at the development of instabilities, and during a decay of the dense plasma column, when hard x-rays and fusion-produced neutrons were generated. The temporal uncertainty of these observations was about 2 ns, and the spatial one amounted to 40 mu m. The filamentation seems be a natural and spontaneous process which occurs in high-current, hot, and dense plasmas produced in plasma focus devices. The observed filaments have usually longitudinal and/or azimuthal orientations. Their higher plasma density and appearance in regions of the measured and assumed current flows can be interpreted as the formation of plasma-current filaments with concentrated magnetic energy. These filamentary effects should be studied due to their possible role during the evolution of instabilities and the formation of small sources emitting fast electrons and ions.
Ion emission from plasmas produced by femtosecond pulses of short-wavelength free-electron laser radiation focused on massive targets: an overview and comparison with long-wavelength laser a
- Autoři: Krása, J., Nassisi, V., Burian, T., Hájková, V., Chalupský, J., Jelínek, Š., Frantálová, K., Krupka, M., Kuglerová, Z., Sushil Kumar Singh, Ph.D., Vyšín, L., Ing. Jakub Cikhardt, Ph.D., Juha, L.
- Publikace: Proc. SPIE 12578, Optics Damage and Materials Processing by EUV/X-ray Radiation (XDam8). Bellingham (stát Washington): SPIE, 2023. Proceedings of SPIE. vol. 12578. ISSN 0277-786X. ISBN 978-1-5106-6276-6.
- Rok: 2023
- DOI: 10.1117/12.2670113
- Odkaz: https://doi.org/10.1117/12.2670113
- Pracoviště: Katedra fyziky
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Anotace:
We report on ion emission from plasma produced on thick targets irradiated with nanosecond and femtosecond pulses delivered by mid-ultraviolet and soft x-ray lasers, respectively. To distinguish between different ion acceleration mechanisms, the maximum kinetic energy of ions produced under different interaction conditions is plotted versus laser fluence. The transformation of the time-of-flight detector signal into ion charge density distance-of-flight spectra makes it possible to determine the mean kinetic energy of the fastest ion groups based on the influence of the acoustic velocity of ion expansion. This allows obtaining additional characteristics of the ion production. The final energy of the group of fast ions determined using the ion sound velocity model is an order of magnitude larger in the fs-XFEL interaction than in the ns-UV one. On the contrary, the ablation yield of ions in our experiment is seven orders of magnitude greater when applying ns-UV laser pulses, not only due to higher energies of UV laser pulses, but also due to a significant difference in interaction and ion formation mechanisms.
Observation of filaments in mega-ampere dense plasma focus within pure deuterium by means of simultaneous schlieren and interferometry diagnostics
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Auluck, S., Sadowski, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Szymaszek, A., Tomaszewski, K.
- Publikace: PHYSICS OF PLASMAS. 2023, 30 ISSN 1089-7674.
- Rok: 2023
- DOI: 10.1063/5.0124093
- Odkaz: https://doi.org/10.1063/5.0124093
- Pracoviště: Katedra fyziky
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Anotace:
Fifteen-frames interferometric diagnostics at the PF-1000 facility was enhanced by adding four frames of the schlieren diagnostics and by splitting of four channels in the optical delay line. This setup enabled the visualization of gradients in the plasma density perpendicular to the direction of the diagnostic laser beam, and their relationship with larger structures visualized by using laser interferometry. The schlieren pictures showed filamentary structures of submillimeter 200–300 lm diameter in shots performed with pure deuterium filling. Filaments were observed in a thin (millimeter-thick) lateral-boundary layer, in lobules, and in internal fast transforming regions of the dense plasma column. Their high-density gradients and location in the regions of recorded (or inferred) currents indicated local concentrations of the magnetic field and current distribution. Millimeter- and submillimeter-size sources of fast charged particles, which were identified in the recorded ion pinhole pictures, have been conjectured to be a manifestation of high local concentrations of the magnetic energy.
Strongly magnetized plasma produced by interaction of nanosecond kJ-class laser with snail targets
- Autoři: Pisarczyk, T., Renner, O., Dudzak, R., Chodukowski, T., Rusiniak, Z., Dostál, J., Krupka, M., prof. Ing. Daniel Klír, Ph.D., Domański, J., Krása, J., Ing. Jakub Cikhardt, Ph.D., Jelínek, Š., Krůs, M.
- Publikace: Plasma Physics and Controlled Fusion. 2023, 65(5), ISSN 0741-3335.
- Rok: 2023
- DOI: 10.1088/1361-6587/acc421
- Odkaz: https://doi.org/10.1088/1361-6587/acc421
- Pracoviště: Katedra fyziky
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Anotace:
Magnetized plasma studies are necessary for many applied studies, including laser-driven inertial fusion, modeling astrophysically relevant phenomena, and innovative industrial and medical applications. An interesting method of generating highly magnetized plasma can be based on the interaction of a laser with spiral-shaped cavity (snail-like) targets. A target shaped in this way can represent the central area of a spherical pellet that is not irradiated radially, but rather through an entrance hole allowing the laser beam to almost impact its inner surface tangentially (Pisarczyk et al 2018 Sci. Rep. 8 17 895). In the reported experiment, snail targets of various diameters were irradiated by linearly or circularly polarized radiation of a Prague asterix laser system (PALS) iodine laser delivering ∼500 J, 350 ps and 1.315 μm pulses on targets. Three-frame complex interferometry demonstrated that plasma is generated on the entire inside and outside surfaces of the snail target, starting from the very beginning of the laser-target interaction. The time-resolved records of the magnetic field and the electron density distribution inside and outside the snail target characterize the changes in the structure of the magnetized plasma. Inside the target, the magnetic field survives long after the termination of the laser-matter interaction, namely longer than 10 ns. Compared to a circularly polarized laser pulse, the irradiation of targets with a p-polarized beam increases both the emission of hot electrons (HEs) and the intensity of the magnetic field. The emission of HEs is not isotropic, and their energy distribution cannot be characterized by a single temperature.
Ultra-high efficiency bremsstrahlung production in the interaction of direct laser-accelerated electrons with high-Z material
- Autoři: Tavana, P., Bukharskii, N., Gyrdymov, M., Spillmann, U., Zähter, S., Ing. Jakub Cikhardt, Ph.D., Borisenko, N.G., Korneev, P., Jacoby, J., Spielmann, C., Andreev, N.E., Guenther, M.M., Rosmej, O.N.
- Publikace: Frontiers in Physics. 2023, 11 1-11. ISSN 2296-424X.
- Rok: 2023
- DOI: 10.3389/fphy.2023.1178967
- Odkaz: https://doi.org/10.3389/fphy.2023.1178967
- Pracoviště: Katedra fyziky
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Anotace:
High performance of laser-driven sources of radiation is in focus of research aimed at the study of high energy density matter, pair production and neutron generation using kJ PW-laser systems. In this work, we present a highly efficient approach to generate an ultra-high flux, high-energy bremsstrahlung in the interaction of direct laser-accelerated (DLA) electrons with a several-millimeters-thick high-Z converter. A directed beam of direct laser-accelerated electrons with energies up to 100 MeV was produced in the interaction of a sub-ps laser pulse of moderate relativistic intensity with long-scale plasma of near-critical density obtained by irradiation of low-density polymer foam with an ns laser pulse. In the experiment, tantalum isotopes generated via photonuclear reactions with threshold energies above 40 MeV were observed. The Geant4 Monte Carlo code, with the measured electron energy and angular distribution as input parameters, was used to characterize the bremsstrahlung spectrum responsible for the registered yields of isotopes from Ta-180 to Ta-175. It is shown that when the direct laser-accelerated electrons interact with a tantalum converter, the directed bremsstrahlung with an average photon energy of 18 MeV and similar to 2 center dot 10(11) photons per laser shot in the energy range of giant dipole resonance (GDR) and beyond (>= 7.5 MeV) is produced. This results in an ultra-high photon flux of similar to 6 x 10(22) sr(-1)center dot s(-1) and a record conversion efficiency of 2% of the focused laser energy into high-energy bremsstrahlung.
Dynamics of implosion phase of modified plasma focus studied via laser interferometry and electrical measurements
- Autoři: Ing. Jakub Malíř, prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Paduch, M.
- Publikace: PHYSICS OF PLASMAS. 2022, 29(9), ISSN 1089-7674.
- Rok: 2022
- DOI: 10.1063/5.0098124
- Odkaz: https://doi.org/10.1063/5.0098124
- Pracoviště: Katedra fyziky
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Anotace:
Dynamics of the implosion of the dense plasma focus play an essential role in converting electrical energy into the kinetic energy of the current sheath and subsequent production of accelerated electrons, ions, hard X-ray, and neutron emission. This paper presents the analysis of the implosion parameters, such as the implosion velocity and imploding mass, coupled with electrical parameters observed on the PF-1000 facility with a modified electrode system. The first two parameters are based on the 16-frame Mach–Zehnder interferometer, which provides the spatial distribution of electron density in a time sequence. Measurement of the total current, current derivative, and voltage enables us to evaluate the total inductance and kinetic energy driven by the capacitor bank. Then comparing the inductances and kinetic energies evaluated from the interferograms and electrical waveforms can provide more precise information on the current flowing in the imploding sheath. We present a possible way to deal with the fact that only part of the total current flows through the imploding layer. With the supposition that the rest of the current flows close to the insulator, we conclude that roughly 70% of the total current flows through the pinch, which is in good agreement with an input parameter of the Lee model, for example.
Influence of the magnetic field on properties of hot electron emission from ablative plasma produced at laser irradiation of a disc-coil target
- Autoři: Pisarczyk, T., Renner, O., Dudžák, R., Chodukowski, T., Rusiniak, Z., Domanski, J., Badziak, J., Dostál, J., Krupka, M., Singh, S., prof. Ing. Daniel Klír, Ph.D., Ehret, M., Gajdoš, P., Zaras-Szydłowska, A., Rosiński, M., Tchórz, P., Szymanski, M., Krása, J., Burian, T., Pfeifer, M., Ing. Jakub Cikhardt, Ph.D., Jelínek, Š., Kocurková, G., Batani, D., Batani, K., Santos, J., Vlachos, C., Ospina-Bohórquez, V., Volpe, L., Borodziuk, S., Krůs, M., Juha, L.
- Publikace: Plasma Physics and Controlled Fusion. 2022, 64(11), 1-16. ISSN 1361-6587.
- Rok: 2022
- DOI: 10.1088/1361-6587/ac95c4
- Odkaz: https://doi.org/10.1088/1361-6587/ac95c4
- Pracoviště: Katedra fyziky
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Anotace:
Optical generators of strong magnetic fields based on the laser-driven-coil target concept are considered to be useful tools for studies of magnetized plasmas in particular, for the study of implosion of magnetized fusion targets in inertial fusion research and astrophysical applications. This paper presents the results of the research directed at an investigation of the plasma properties in a laser-induced magnetic field. In the experiment carried out on the kilojoule PALS laser facility, a generator of the magnetic field was a disc-coil (DC) target composed of a Cu disk coupled to a single-turn coil irradiated by a 1ω laser beam with an energy of 500 J. The attention was focused on examining the influence of the magnetic field on properties of the hot electron (HE) flux emitted from the front surface of the irradiated target. The three-frame complex interferometry and four-frame x-ray camera combined with the measurements of the HE population and energy using a multi-channel magnetic electron spectrometer and 2D-resolved imaging of the induced Cu Kα line emission were applied to characterize the ablative plasma and the generated particles. Based on the measured angular distributions of the electron energy spectra, 3D simulations have been performed to visualize the effect of the magnetic field on the HE flux and to provide information on space-time distribution of the electron and current density both without and with the presence of an axial magnetic field. The obtained results confirmed the possibility of generating magnetic fields above 5 T using the proposed DC target design as well as the significant impact of these fields on properties of the ablative plasma and the HE emission.
Investigation of magnetized plasma created in snail targets at the PALS facility
- Autoři: Pisarczyk, T., Renner, O., Dudzak, R., Chodukowski, T., Krupka, M., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Krůs, M.
- Publikace: 48th EPS Conference on Plasma Physics, EPS 2022. Mulhouse: European Physical Society, 2022. vol. 46A. ISBN 979-10-96389-16-2.
- Rok: 2022
- Pracoviště: Katedra fyziky
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Anotace:
Magnetized plasma studies are necessary for many applications including laser-driven inertial fusion, modeling astrophysics relevant phenomena, as well as innovative industrial and medical applications. The presented research continues in previous PALS experiments, which principally confirmed the idea of forming the magnetized plasma in snail targets (ST) irradiated by moderate intensity laser beams.
Laser-generated supersonic plasma jets and shocks in a transverse magnetic field
- Autoři: Bohlin, H., Brack, F.-E., Cervenak, M., Chodukowski, T., Ing. Jakub Cikhardt, Ph.D., Hübner, J., Jelínek, Š., prof. Ing. Daniel Klír, Ph.D., Krupka, M., Krůs, M.
- Publikace: Plasma Physics and Controlled Fusion. 2022, 64(8), ISSN 0741-3335.
- Rok: 2022
- DOI: 10.1088/1361-6587/ac7416
- Odkaz: https://doi.org/10.1088/1361-6587/ac7416
- Pracoviště: Katedra fyziky
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Anotace:
The influence of a transverse magnetic field on the formation and evolution of supersonic plasma jets and shocks was studied experimentally, and compared with 3D numerical simulations. An improved jet collimation was seen due to the change in the magnetic field topology restricting the radial expansion of the ablated plasma. The magnetic field was also shown to strongly affect the shock structures, both indirectly through the modified jet geometry, as well as due to a compression of the field lines in the shock region. The interaction characteristics were found to depend on the relative contribution of the magnetic and plasma pressure in balancing the ram pressure of the jet.
Novel concept suppressing plasma heat pulses in a tokamak by fast divertor sweeping
- Autoři: Horáček, J., Lukeš, S., Adámek, J., Havlíček, J., Entler, S., Seidl, J., Cavalier, J., Ing. Jakub Cikhardt, Ph.D., Sedmidubsky, V.
- Publikace: Scientific Reports. 2022, 12 ISSN 2045-2322.
- Rok: 2022
- DOI: 10.1038/s41598-022-18748-x
- Odkaz: https://doi.org/10.1038/s41598-022-18748-x
- Pracoviště: Katedra fyziky
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Anotace:
One of the remaining challenges in magnetic thermonuclear fusion is survival of the heat shield protecting the tokamak reactor vessel against excessive plasma heat fluxes. Unmitigated high confinement edge localized mode (ELM) is a regular heat pulse damaging the heat shield. We suggest a novel concept of magnetic sweeping of the plasma contact strike point fast and far enough in order to spread this heat pulse. We demonstrate feasibility of a dedicated copper coil in a resonant circuit, including the induced currents and power electronics. We predict the DEMO ELM properties, simulate heat conduction, 3D particles motion and magnetic fields of the plasma and coil in COMSOL Multiphysics and Matlab. The dominant system parameter is voltage, feasible 18 kV yields 1 kHz sweeping frequency, suppressing the ELM-induced surface temperature rise by a factor of 3. Multiplied by other known mitigation concepts, ELMs might be mitigated enough to ensure safe operation of DEMO.
Temporal behavior of hard x-ray and neutron production in plasma focus discharges
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Tomaszewski, K., Sadowski, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Szymaszek, A.
- Publikace: PHYSICS OF PLASMAS. 2022, 29 ISSN 1089-7674.
- Rok: 2022
- DOI: 10.1063/5.0085351
- Odkaz: https://doi.org/10.1063/5.0085351
- Pracoviště: Katedra fyziky
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Anotace:
This paper concerns the correlation of hard x-ray and neutron signals, which were recorded with scintillation detectors oriented in the axial and radial directions, in a comparison with interferometric and extreme-ultraviolet radiation frames, as recorded within the plasma focus (PF)-1000 facility operated with a deuterium filling. The considered signals showed two different phases. In the initial phase, the fusion neutrons are mainly produced by deuterons moving dominantly downstream during the disruption of a pinch constriction (lasting tens nanoseconds). In the later phase (usually after about 100 ns), the fusion neutron emission reaches its maximum in the radial directions. This emission (lasting 100–200 ns) is caused by the fast deuterons moving in both the downstream and radial directions. It correlates usually with a decay of dense plasma structures in remnants of the expanding pinch column. This can be explained by a decay of internal magnetic fields. The neutron signal is usually composed of several sub-pulses of different energies. It was deduced that the primary deuterons producing the observed fusion neutrons undergo a regular and repeated temporal, directional, and energy evolution.
Ablation instability experimentally observed on the thin foil metal target surface during its irradiation by terawatt laser
- Autoři: Krupka, M., Krása, J., Singh, S., Dostál, J., Kálal, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: 47th EPS Conference on Plasma Physics, EPS 2021. Mulhouse: European Physical Society, 2021. p. 345-348. Europhysics conference abstracts. vol. 45A. ISBN 978-1-7138-3704-6.
- Rok: 2021
- Pracoviště: Katedra fyziky
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Anotace:
Time evolution of plasma density modulations in case of thin foil metal targets was observed during the irradiation with focused terawatt iodine PALS laser beam. These modulations were simultaneously recorded using femtosecond interferometry in three time frames and x-ray streak camera allowing to determine growth and decay rates of hydrodynamic instabilities. These modulations were observed during the laser-plasma interaction, in particular several hundred picoseconds before its maximum intensity. Hot electron emission characteristics were measured and analyzed using an angular array of electron spectrometers. Weaker emission of hot electrons from the lead plasma was observed in comparison to lower Z materials.
Characteristics of fast deuteron sources generated in a dense plasma focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kwiakowski, R., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Szymaszek, A., Tomaszewski, K., Zaloga, D., Zielinska, E., Akel, M.
- Publikace: EUROPEAN PHYSICAL JOURNAL PLUS. 2021, 136(7), ISSN 2190-5444.
- Rok: 2021
- DOI: 10.1140/epjp/s13360-021-01799-w
- Odkaz: https://doi.org/10.1140/epjp/s13360-021-01799-w
- Pracoviště: Katedra fyziky
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Anotace:
The paper characterizes sources of the fast deuterons which can produce the D–D fusion neutrons. Two pinhole cameras, the axial one and the slant one (oriented at 0° and 60° in relation to the z-axis), were equipped with solid-state nuclear track detectors and applied to investigate the fast deuterons of energies about 100 keV, which produce small quasi-circular track spots of diameters ranging (1–3) mm. They are often observed in plasma-focus shots with higher neutron yields, when they constitute a part of the recorded ion images in a form of azimuthal arcs and/or radial strips. An analysis of an influence of the global magnetic field, which acts along the fast deuteron trajectories, made it possible to determinate the deuteron sources localization, also outside the dense plasma column. The recorded spatial distribution of the fast deuterons, their temporal correlation with disruptions of the ordered plasma structures inside and outside the pinch column, and a regular evolution of the energy of fast deuterons—indicate their strong interconnection and the link with filamentary structure of the current flow.
K-shell radiation and neutron emission from z-pinch plasmas generated by hybrid gas-puff implosions onto on-axis wires
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A. V., Kokshenev, V. A., Cherdizov, R. K., Ing. Jakub Cikhardt, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Malíř, Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2021, 28(6), ISSN 1070-664X.
- Rok: 2021
- DOI: 10.1063/5.0054683
- Odkaz: https://doi.org/10.1063/5.0054683
- Pracoviště: Katedra fyziky
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Anotace:
Z-pinches have been explored as efficient soft x-ray sources for many years. To optimize x-ray emission, various z-pinch configurations were tested. This paper presents data obtained with a hybrid gas-puff z-pinch imploding onto on-axis wires on a microsecond, multi-megaampere GIT-12 generator. In our previous experiments, the hybrid gas puff, i.e., an inner deuterium gas puff surrounded by an outer hollow cylindrical plasma shell, was used to produce energetic protons, deuterons, and neutrons up to 60MeV [Klir et al., New J. Phys. 22, 103036 (2020)]. The behavior of the hybrid gas-puff z-pinch on GIT-12 was interpreted as a high-density plasma opening switch with a microsecond conduction time, 3 MA conduction current, nanosecond opening, and up to 60MV stand-off voltage. These properties can be employed to transfer the current into an on-axis load with a high rise rate. In the recent experiments on GIT-12, we therefore placed single or multiple aluminum wires on the axis of the hybrid gas-puff z-pinch. Before a current sheath arrived at the axis, a coronal plasma was seen around the wire. A rapid increase in x-ray radiation was observed when the coronal plasma imploded onto the axis. The coronal plasma implosion resulted in a long (2cm), narrow (similar to mm) column radiating in the Al K-shell lines. With the single Al wire of 80 mu m diameter, the K-shell x-ray output reached 5.5 +/- 0.8kJ in a 0.6 +/- 0.1 TW peak power and 7 +/- 1ns pulse. The higher K-shell yield of 12 +/- 2kJ and peak K-shell power of 0.7 +/- 0.1 TW were achieved with four 38 mu m diameter Al wires. (Their cross section formed the corners of a square with 1mm side.) The presence of the wires on the axis significantly suppressed ion acceleration and neutron production. Deuterium-deuterium (DD) neutron yields of about 1.2x10(11) were 20 times smaller than the yields produced in shots without any wire. The DD neutron yield was increased up to 4.5x10(11) when the Al wire was replaced by a fiber fr
Mapping of azimuthal B-fields in Z-pinch plasmas using Z-pinch-driven ion deflectometry
- Autoři: Ing. Vojtěch Munzar, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Malíř, Ing. Jan Novotný, Ing. Karel Řezáč, Ph.D., Shishlov, A.V., Kokshenev, V.A., Cherdizov, R.K., Ratakhin, N.A.
- Publikace: PHYSICS OF PLASMAS. 2021, 28(6), 062702-1-062702-18. ISSN 1089-7674.
- Rok: 2021
- DOI: 10.1063/5.0040515
- Odkaz: https://doi.org/10.1063/5.0040515
- Pracoviště: Katedra fyziky
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Anotace:
B-field measurements are crucial for the study of high-temperature and high-energy-density plasmas. A successful diagnostic method, ion deflectometry (radiography), is commonly employed to measure MGauss magnetic fields in laser-produced plasmas. It is based on the detection of multi-MeV ions, which are deflected in B-fields and measure their path integral. Until now, protons accelerated via laser–target interactions from a point-like source have been utilized for the study of Z-pinch plasmas. In this paper, we present the results of the first Z-pinch-driven ion deflectometry experiments using MeV deuterium beams accelerated within a hybrid gas-puff Z-pinch plasma on the GIT-12 pulse power generator. In our experimental setup, an inserted fiducial deflectometry grid (D-grid) separates the imploding plasma into two regions of the deuteron source and the studied azimuthal B-fields. The D-grid is backlighted by accelerated ions, and its shadow imprinted into the deuteron beams demonstrates ion deflections. In contrast to the employment of the conventional point-like ion source, in our configuration, the ions are emitted from the extensive and divergent source inside the Z-pinch. Instead of having the point ion source, deflected ions are selected via a point projection by a pinhole camera before their detection. Radial distribution of path-integrated B-fields near the axis (within a 15 mm radius) is obtained by analysis of experimental images (deflectograms). Moreover, we present a 2D topological map of local azimuthal B-fields B(r,z) via numerical retrieval of the experimental deflectogram.
Measurement of strong electromagnetic pulses generated from solid targets at sub-ns kJ-class PALS laser facility
- Autoři: Raczka, P., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Krása, J., Krupka, M., Burian, T., Krůs, M., Pisarczyk, T., Dostál, J., Dudžák, R., Badziak, J.
- Publikace: Plasma Physics and Controlled Fusion. 2021, 63(8), 1-17. ISSN 0741-3335.
- Rok: 2021
- DOI: 10.1088/1361-6587/ac087f
- Odkaz: https://doi.org/10.1088/1361-6587/ac087f
- Pracoviště: Katedra fyziky
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Anotace:
Measurements had been performed of strong electromagnetic pulses (EMPs) generated as a result of laser-target interaction at the sub-ns kJ-class Prague Asterix Laser System facility. Two conductive Prodyn FD5C D-dot pencil probes were used. Measurements were performed inside the experimental chamber and outside the chamber in a large chamber window 40 cm in diameter in a setup that guaranteed 6 GHz bandwidth. A very good signal-to-noise ratio (17:1) was obtained after some steps were taken to ensure proper EMP shielding of the data collection setup. The EMP signal in the time domain was found to have the form of a sharp initial spike followed by gradually decaying oscillations interspersed with some secondary spikes. The values of the vertical component of the electric field strength were estimated. The highest value recorded in this experiment was 620(-180)(+260) kV m(-1) at a distance of 40 cm from the target. It was observed that plastic targets-particularly the 100s of mu m thick plastic foils-tend to generate stronger EMP fields than Cu and Au targets. A time-frequency analysis was performed for a typical shot, clearly showing some spectral features that appear only sometime after the start of the signal and hence indicate EMP generation from secondary sources. Electrons ejected from the target were recorded with the energies exceeding 1.5 MeV, which indicates that highly energetic processes are triggered as a result of the laser-target interaction.
Optimizing of Experimental Load of PFZ-200 Plasma Focus
- Autoři: Ing. Jan Novotný, Ing. Jakub Cikhardt, Ph.D., Kravárik, J., prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: IEEE Transactions on Plasma Science. 2021, 49(1), 450-454. ISSN 0093-3813.
- Rok: 2021
- DOI: 10.1109/TPS.2020.3041329
- Odkaz: https://doi.org/10.1109/TPS.2020.3041329
- Pracoviště: Katedra fyziky
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Anotace:
This article presents a study of neutron emission on the PFZ-200 plasma focus at the Department of physics on FEE CTU in Prague, Czech Republic. In order to achieve the highest and most stable neutron yields, the deuterium working gas pressure and the anode shape were systematically varied. We observed the plasma time to the pinch and the discharge current by the Rogowski coil and neutron emission by the silver activation detector and scintillation time-of-flight detectors. The imploded plasma was visualized using a fast X-ray pinhole camera with a gated microchannel plate detector. The experiment presents the z-pinch discharges with the current maximum above 200 kA and the average neutron yields of 3×10^8 neutrons/shot. Measured pinch times were in the range from 1.65 to 1.85 μs . The hollow round anode configuration performed the most stable neutron yields with a deviation under 20%.
Radiative characterization of supersonic jets and shocks in a laser-plasma experiment
- Autoři: Bohlin, H., Brack, F., Cervenak, M., Chodukowski, T., Ing. Jakub Cikhardt, Ph.D., Hübner, J., Jelínek, Š., prof. Ing. Daniel Klír, Ph.D., Krupka, M., Krůs, M.
- Publikace: Plasma Physics and Controlled Fusion. 2021, 63(4), ISSN 0741-3335.
- Rok: 2021
- DOI: 10.1088/1361-6587/abe526
- Odkaz: https://doi.org/10.1088/1361-6587/abe526
- Pracoviště: Katedra fyziky
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Anotace:
The interaction of supersonic laser-generated plasma jets with a secondary gas target was studied experimentally. The plasma parameters of the jet, and the resulting shock, were characterized using a combination of multi-frame interferometry/shadowgraphy, and x-ray diagnostics, allowing for a detailed study of their structure and evolution. The velocity was obtained with an x-ray streak camera, and filtered x-ray pinhole imaging was used to infer the electron temperature of the jet and shock. The topology of the ambient plasma density was found to have a significant effect on the jet and shock formation, as well as on their radiation characteristics. The experimental results were compared with radiation hydrodynamic simulations, thereby providing further insights into the underlying physical processes of the jet and shock formation and evolution.
Variance of DD-neutron yield in laser fusion experiments
- Autoři: Krása, J., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D., Pfeifer, M., Burian, T., Dudžák, R., Dostál, J., Krupka, M., Singh, S., Juha, L., Krůs, M.
- Publikace: 47th EPS Conference on Plasma Physics, EPS 2021. Mulhouse: European Physical Society, 2021. p. 537-540. Europhysics conference abstracts. vol. 45A. ISBN 978-1-7138-3704-6.
- Rok: 2021
- Pracoviště: Katedra fyziky
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Anotace:
This contribution deals with experimental observations of the yield of DD fusion in deuterated plastic targets irradiated by 300-ps 3-TW laser system PALS. To perform the analysis of variance for neutron yield values, Yn, in the range of 105- 109observed in a relatively narrow range of laser energy E from 500 - 700 J, the observed yield values were included in a neutron-yield - laser-energy (Yn-E) diagram showing general trends in the energy yield scaling Yn(E). This dependence is characterized by a power law, Yn= Q E1.65, where Q is the parameter reflecting possible dependence on the pulse duration, laser intensity, laser contrast ratio, focal geometry, target structure, etc. [1]. The analysis we present shows that, despite shot-to-shot fluctuations, the variance of Q values from 14 - 5.2×104for the narrow range of laser energy obtained in PALS experiments can be elucidated by the influence of some nonlinear processes affecting ion acceleration.
Characteristics of closed currents and magnetic fields outside the dense pinch column in a plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, J.M., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kwiatkowski, R., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Szymaszek, A., Tomaszewski, K., Zielinska, E., Zaloga, D., Akel, M.
- Publikace: PHYSICS OF PLASMAS. 2020, 27 092702-1-092702-10. ISSN 1070-664X.
- Rok: 2020
- DOI: 10.1063/5.0010249
- Odkaz: https://doi.org/10.1063/5.0010249
- Pracoviště: Katedra fyziky
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Anotace:
This paper describes the structure of a higher extreme ultraviolet (XUV) emission and plasma density region which surrounds a pinched dense-plasma column. It is interpreted as a toroidal-like plasma formation, which is flowing by a closed current with poloidal and toroidal components upon its surface. This current produces a local magnetic field, which separates the external discharge current from the surface of the dense pinch column. We estimated the values of closed currents as well as magnetic- and plasma-pressures in this column and its surrounding on the basis of the measured distribution of interferometric fringes and intense XUV emission, recorded during the pinch stagnation phase. The considered layer forms the region in which the magnetic energy can be conserved, and during its decay, the acceleration of fast deuterons can take place.
Effect of expanding plasma on propagation of electromagnetic pulses by laser-plasma interaction
- Autoři: Krasa, J., Consoli, F., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., De Angelis, R., Krupka, M., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Dostál, J., Krůs, M., Dudžák, R.
- Publikace: Plasma Physics and Controlled Fusion. 2020, 62(2), 1-8. ISSN 0741-3335.
- Rok: 2020
- DOI: 10.1088/1361-6587/ab5c4e
- Odkaz: https://doi.org/10.1088/1361-6587/ab5c4e
- Pracoviště: Katedra fyziky
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Anotace:
Experiments were performed using the Prague Asterix Laser System to study the effect of expanding plasma on electromagnetic pulse propagation (EMP) in the interaction chamber in an intensity regime of 10(16)Wcm(-2). Similar to the interaction that occurs between radio waves and the ionosphere, the expansion of laser-produced plasma causes the vacuum chamber to be gradually filled with inhomogeneous plasma that interacts with the emitted EMP. Combining the space-time analysis of a plasma density inside the interaction chamber and the fast Fourier transform filtering of antenna signals, we have resolved the influence of the expanding plasma on space-time characteristics of EMP.
Hot electron retention in laser plasma created under terawatt subnanosecond irradiation of Cu targets
- Autoři: Pisarczyk, T., Kálal, M., Gus'kov, S., Batani, D., Renner, O., Santos, J., Dudzak, R., Chodukowski, T., Krupka, M., Ing. Jakub Cikhardt, Ph.D., Krůs, M., prof. RNDr. Pavel Kubeš, CSc.,
- Publikace: Plasma Physics and Controlled Fusion. 2020, 62(11), ISSN 0741-3335.
- Rok: 2020
- DOI: 10.1088/1361-6587/abb74b
- Odkaz: https://doi.org/10.1088/1361-6587/abb74b
- Pracoviště: Katedra fyziky
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Anotace:
Laser plasma created by intense light interaction with matter plays an important role in high-energy density fundamental studies and many prospective applications. Terawatt laser-produced plasma related to the low collisional and relativistic domain may form supersonic flows and is prone to the generation of strong spontaneous magnetic fields. The comprehensive experimental study presented in this work provides a reference point for the theoretical description of laser-plasma interaction, focusing on the hot electron generation. It experimentally quantifies the phenomenon of hot electron retention, which serves as a boundary condition for most plasma expansion models. Hot electrons, being responsible for nonlocal thermal and electric conductivities, are important for a large variety of processes in such plasmas. The multiple-frame complex-interferometric data providing information on time resolved spontaneous magnetic fields and electron density distribution, complemented by particle spectra and x-ray measurements, were obtained under irradiation of the planar massive Cu and plastic-coated targets by the iodine laser pulse with an intensity of above 10(16)W cm(-2). The data shows that the hot electron emission from the interaction region outside the target is strongly suppressed, while the electron flow inside the target,i.e.in the direction of the incident laser beam, is a dominant process and contains almost the whole hot electron population. The obtained quantitative characterization of this phenomenon is of primary importance for plasma applications spanning from ICF to laser-driven discharge magnetic field generators.
Ion acceleration and neutron production in hybrid gas-puff z-pinches on the GIT-12 and HAWK generators
- Autoři: prof. Ing. Daniel Klír, Ph.D., Jackson, S. L., Shishlov, A., Kokshenev, V. A., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Vojtěch Munzar, Ph.D.,
- Publikace: Matter and Radiation at Extremes. 2020, 5(2), 026401-1-026401-10. ISSN 2468-2047.
- Rok: 2020
- DOI: 10.1063/1.5132845
- Odkaz: https://doi.org/10.1063/1.5132845
- Pracoviště: Katedra fyziky
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Anotace:
Z- pinch experiments with a hybrid configuration of a deuterium gas puff have been carried out on the HAWK (NRL, Washington, DC) and GIT-12 (IHCE, Tomsk) pulsed power generators at 0.7 MA and 3 MA currents, respectively. On GIT-12, neutron yields reached an average value of 2 X 10(12) neutrons, and deuterons were accelerated up to an energy of 30 MeV. This was 50 times the ion energy provided by the generator driving voltage of 0.6 MV and the highest energy observed in z-pinches and dense plasma foci. To confirm these unique results independently on another device, we performed several experimental campaigns on the HAWK generator. Comparison of the experiments on GIT-12 and HAWK helped us to understand which parameters are essential for optimized neutron production. Since the HAWK generator is of a similar pulsed power architecture as GIT-12, the experiments on GIT-12 and HAWK are important for the study of how charged-particle acceleration scales with the current. (C) 2020 Author(s).
Ion bursts and multi-electron population in expanding laser-produced plasma
- Autoři: Krása, J., prof. Ing. Daniel Klír, Ph.D., Krupka, M., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Pisarczyk, T., Dostál, J., Ing. Karel Řezáč, Ph.D., Krůs, M., Kálal, M.
- Publikace: Journal of Instrumentation. 2020, 15(5), ISSN 1748-0221.
- Rok: 2020
- DOI: 10.1088/1748-0221/15/05/C05046
- Odkaz: https://doi.org/10.1088/1748-0221/15/05/C05046
- Pracoviště: Katedra fyziky
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Anotace:
We present an experimental study of emission of relativistic electrons, fast ions and DD-fusion neutrons produced by interaction of sub-nanosecond laser radiation with solid targets performed at the PALS facility. Measurements of electron density close to the target surface using the femtosecond interferometry, energy distribution functions of hot electrons far from the target, and time-of-flight spectra of ions are performed. A multi population of electrons is formed as the laser interaction with plasma proceeds. Ions accelerated by hot electrons to MeV energy are emitted in bursts. The neutron yield from the deuterated target is compared to yields obtained from other experiments. Constraint of non-linear processes on the ion acceleration and resulting neutron yields is shown.
Laser produced electromagnetic pulses: generation, detection and mitigation
- Autoři: Consoli, F., Tikhonchuk, V.T., Bardon, M., Bradford, P., Carroll, D.C., Ing. Jakub Cikhardt, Ph.D., Cipriani, M., Clarke, R.J., Cowan, T.E., Danson, C.N.
- Publikace: High Power Laser Science and Engineering. 2020, 8 1-59. ISSN 2095-4719.
- Rok: 2020
- DOI: 10.1017/hpl.2020.13
- Odkaz: https://doi.org/10.1017/hpl.2020.13
- Pracoviště: Katedra fyziky
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Anotace:
This paper provides an up-to-date review of the problems related to the generation, detection and mitigation of strong electromagnetic pulses created in the interaction of high-power, high-energy laser pulses with different types of solid targets. It includes new experimental data obtained independently at several international laboratories. The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce. The major emphasis is put on the GHz frequency domain, which is the most damaging for electronics and may have important applications. The physics of electromagnetic emissions in other spectral domains, in particular THz and MHz, is also discussed. The theoretical models and numerical simulations are compared with the results of experimental measurements, with special attention to the methodology of measurements and complementary diagnostics. Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions, which may have promising applications.
Laser-Target Experiments at PALS for Deuterium Plasma Beam Fusion
- Autoři: Krasa, J., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Hora, H., Krupka, M., Ing. Karel Řezáč, Ph.D.,
- Publikace: Acta Physica Polonica A. 2020, 138(4), 579-585. ISSN 0587-4246.
- Rok: 2020
- DOI: 10.12693/APhysPolA.138.579
- Odkaz: https://doi.org/10.12693/APhysPolA.138.579
- Pracoviště: Katedra fyziky
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Anotace:
The Prague Asterix Laser System (PALS) is a terawatt iodine laser (1.2 kJ, 350 ps, 1315 nm), designed to deliver irradiance on target of about 3 x 10(16) W/cm(2). The PALS laser together with a Ti:sapphire laser (1 J, 50 fs, 800 nm) is used for experiments allowing femtosecond probing of laser-produced plasma. We present an experimental study of emission of hot electrons, fast ions and fusion neutrons generated through the H-2(d;n)He-3 fusion reaction of deuterons. During the laser-plasma interaction and plasma expansion, a multi-population of electrons appears. Non-isotropic emission of fast as well as thermal electrons is typical for the interaction of nanosecond laser radiation with plasma. The production of relativistic electrons makes it possible to accelerate protons to MeV energy and generate fusion neutrons via fusion reactions. The DD-neutron yield is compared to yields obtained from other experiments. Depending on the energy of the laser pulse, it is shown that the competition of laser contrast and laser pulse intensity sets a fundamental constraint on the ion emission and the resultant neutron yield performance of deuterated targets.
Neutron fluence distribution in experiments with 3 MA deuterium gas-puff z-pinch
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Kokshenev, V. A., Ing. Karel Řezáč, Ph.D., Cherdizov, R.K., Dudkin, G.N., Fursov, F.I., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Kurmaev, N.E., Ing. Vojtěch Munzar, Ph.D., Ing. Jan Novotný, Ratakhin, N.A., Varlachev, V.A., Turek, K.
- Publikace: PHYSICS OF PLASMAS. 2020, 27(7), 072705-1-072705-10. ISSN 1070-664X.
- Rok: 2020
- DOI: 10.1063/5.0008108
- Odkaz: https://doi.org/10.1063/5.0008108
- Pracoviště: Katedra fyziky
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Anotace:
Deuterium gas-puff z-pinches are very efficient laboratory sources of neutron pulses. Using a novel hybrid gas-puff load on the GIT-12 generator, a significant increase in the neutron yields up to
Neutron production in cavity pressure acceleration of plasma objects
- Autoři: Chodukowski, T., Borodziuk, S., Rusiniak, Z., Ing. Jakub Cikhardt, Ph.D., Jach, K.
- Publikace: AIP Advances. 2020, 10(8), 1-6. ISSN 2158-3226.
- Rok: 2020
- DOI: 10.1063/5.0005977
- Odkaz: https://doi.org/10.1063/5.0005977
- Pracoviště: Katedra fyziky
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Anotace:
The laser-induced Cavity Pressure Acceleration (CPA) scheme [S. Borodziuk et al., Appl. Phys. Lett. 95, 231501 (2009)] allows for effective transformation of the laser energy into the kinetic energy of plasma streams and dense plasma objects. It has been proven that using long-wavelength laser beams, with relatively low energies (up to 500 J for lambda (1) = 1.315 mu m and FWHM = 350 ps), it is possible to accelerate macroparticles to very high velocities (above 10(7) cm/s). The study of neutron yield showed the benefit of CPA in delivering ion temperatures and density sufficient to reach the thermonuclear region.
Production of energetic protons, deuterons, and neutrons up to 60 MeV via disruption of a current-carrying plasma column at 3 MA
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Kokshenev, V. A., Jackson, S. L., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Vojtěch Munzar, Ph.D.,
- Publikace: New Journal of Physics. 2020, 22(10), 1-17. ISSN 1367-2630.
- Rok: 2020
- DOI: 10.1088/1367-2630/abbab5
- Odkaz: https://doi.org/10.1088/1367-2630/abbab5
- Pracoviště: Katedra fyziky
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Anotace:
Acceleration of ions to multi-MeV energies is investigated in various plasma devices to better understand processes in astrophysical plasmas and to develop efficient accelerators for a variety of applications. This paper reports the production of proton, deuteron, and electron beams in a z-pinch-a cylindrically symmetric plasma column that is compressed by its own magnetic field. For this work, the GIT-12 pulsed-power generator was used to drive a novel configuration of z-pinch that dramatically enhanced ion acceleration associated with disruption of the current by instabilities in the compressed plasma. During the disruption of 3 MA current, hydrogen ions were accelerated up to at least 50 MeV, which is almost a hundred-times the ion energy provided by the generator driving voltage of 0.6 MV. Under optimal conditions, the total numbers of hydrogen ions with energies above 20 and 50 MeV were 4 x 10(13)and 10(11), respectively. Accelerated deuterons produced one 20 ns (full width at half maximum) pulse of fast neutrons via D(d, n)He-3 and other nuclear reactions. A maximum neutron output of (1.0 +/- 0.2) x 10(12)neutrons/sr was observed downstream, i.e., in the anode to cathode direction. In this direction, the maximum neutron energy reached 58 +/- 7 MeV. Both ion and neutron beams in our experiment reached an end-point energy of about 60 MeV, which is the highest value observed in pulsed-power devices. A localized peak voltage of greater than or similar to 60 MV was driven by the inductive energy that was stored around the plasma column and that was extracted during a sub-nanosecond current drop. Considering the natural occurrence of current-carrying columns in laboratory and space plasmas, the current interruption observed in z-pinches could represent a more general physical process that contributes to the efficient conversion of magnetic energy into the energy of particle beams in various plasmas.
Scenario of a magnetic dynamo and magnetic reconnection in a plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, M.J., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kwiatkowski, R., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Szymaszek, R., Tomaszewski, K., Zielinska, E., Akel, M., Ing. Balžima Cikhardtová,
- Publikace: Matter and Radiation at Extremes. 2020, 5 ISSN 2468-2047.
- Rok: 2020
- DOI: 10.1063/1.5133103
- Odkaz: https://doi.org/10.1063/1.5133103
- Pracoviště: Katedra fyziky
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Anotace:
The paper discusses a possible energy transformation that leads to the acceleration of fast ions and electrons. In plasma-focus discharges that occur during deuteriumfilling, which have a maximum current of about 1MA, the accelerated deuterons producefastfusion neutrons andfast electrons hard X-ray emissions. Their total energy, which is of the order of several kilojoules, can be delivered by the discharge through a magnetic dynamo and selforganization to the ordered plasma structures that are formed in a pinch during the several hundreds of nanoseconds of the pinch implosion, stagnation, and evolution of instabilities. This energy is finally released during the decay of the ordered plasma structures in the volume between the anode face and the umbrella front of the plasma and current sheath in the form of induced electric fields that accelerate fast electrons and ions.
Spatial distribution of ion emission in gas-puff z-pinches and dense plasma foci
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Jackson, S. L., Kokshenev, V. A., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Kravárik, J., Ing. Vojtěch Munzar, Ph.D.,
- Publikace: Plasma Physics and Controlled Fusion. 2020, 62(3), 035009-1-035009-13. ISSN 0741-3335.
- Rok: 2020
- DOI: 10.1088/1361-6587/ab6902
- Odkaz: https://doi.org/10.1088/1361-6587/ab6902
- Pracoviště: Katedra fyziky
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Anotace:
Mega-ampere dense plasma foci and deuterium gas-puff z-pinches can accelerate deuterons to multi-MeV energies. Diagnostic measurements of the properties of these ions provide information about ion acceleration in z-pinch plasmas. In particular, the results from ion pinhole cameras seem to be useful for the discussion of ion acceleration mechanisms. Recently, we have used various configurations of ion pinhole cameras in deuterium gas-puff experiments on the GIT-12 generator at the Institute of High Current Electronics in Tomsk and on the HAWK generator at the US Naval Research Laboratory in Washington. The stack of radiochromic films and CR-39 solid-state nuclear track detectors recorded deuterons with energies up to 30 MeV. From our ion diagnostics, we obtained the spatial distribution of the ion source and the ion-beam divergence during the ion emission. This ion-beam divergence was found to decrease with increasing deuteron energy. At 20 MeV, the divergence of each of the individual micro-beams that composed the ion source was on the order of 10 mrad. The deflection of each micro-beam due to the azimuthal magnetic and/or radial electric fields resulted in radial stripes observed by the beam-profile detectors. By analyzing the ion pinhole images, we found that the deuterons were emitted both from a central spot and from a ring-shaped region with a rather large diameter, on the order of 1 cm. The origin and particular diameter of this ring is attributed to the geometry of the electrodes and to the distribution of the current density before the disruption.
Acceleration of protons and deuterons up to 35 MeV and generation of 10(13) neutrons in a megaampere deuterium gas-puff z-pinch
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Kokshenev, V. A., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Buryšková, S., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Jackson, S. L., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Šíla, O.
- Publikace: Plasma Physics and Controlled Fusion. 2019, 61(1), 014018-1-014018-11. ISSN 0741-3335.
- Rok: 2019
- DOI: 10.1088/1361-6587/aadc99
- Odkaz: https://doi.org/10.1088/1361-6587/aadc99
- Pracoviště: Katedra fyziky
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Anotace:
The acceleration of hydrogen ions up to 35 MeV is observed in the z-pinch experiments on the GIT-12 generator at a 3 MA current and 0.6 MV driving voltage. High ion energies are obtained with a novel configuration of a deuterium gas-puff z-pinch. In this configuration, a hollow cylindrical plasma shell is injected around an inner deuterium gas puff to form a homogeneous, uniformly conducting layer between electrodes at the initial phase of z-pinch implosion. The stable implosion at the velocity up to 650 km s(-1) is important to deliver more current onto the z-pinch axis. Magnetohydrodynamic instabilities become apparent first at stagnation. After the disruptive development of m = 0 instabilities, similar to 20 ns pulses of high-energy photons, neutrons, electrons, and ions are observed. The average neutron yield is 2 x 10(12). The ion emission is characterized by various diagnostic techniques including those based on the usage of neutron-producing samples. When a large neutron-producing sample is placed onto the axis below a cathode mesh, the neutron yield is increased up to (1.1 +/- 0.3) x 10(13). Considering a similar to 130 kJ energy input into z-pinch plasmas and magnetic field, this implies the neutron production efficiency of similar to 10(8) neutrons per one Joule of the z-pinch energy.
Comprehensive diagnostics of hot electron emission from plasmas produced by sub-nanosecond terawatt laser on thin foil metal targets
- Autoři: Krupka, M., Krasa, J., Dudzak, R., Ing. Jakub Cikhardt, Ph.D., Kálal, M., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: Journal of Instrumentation. 2019, 14 ISSN 1748-0221.
- Rok: 2019
- DOI: 10.1088/1748-0221/14/12/C12003
- Odkaz: https://doi.org/10.1088/1748-0221/14/12/C12003
- Pracoviště: Katedra fyziky
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Anotace:
Interaction of high-power and high-energy lasers with matter generates plasmas emitting considerable amounts of relativistic electrons. In this contribution such plasmas were produced by PALS kJ laser facility delivering the beam with intensity of the order of 3 . 10(16)W . cm(-2) in 400 ps on thin foil metal targets. To study the emission of hot electrons in horizontal plane around the target, an array of electron spectrometers was employed to record the electron emission from the plasma in several angles around the target. For experimental determination of the total number of hot electrons escaping from the plasma through the plasma barrier a target probe was used in order to measure the target return current which neutralizes the positive target charge produced by these escaping hot electrons. Together with this diagnostics the femtosecond interferometry was used to obtain spatial electron density profiles in close proximity to the irradiated target at selected time delays. Interferograms indicated occurrence of plasma density modulations in front of the target and made it possible to calculate the number of electrons contained within thermal fraction of the plasma produced by the laser. The number of these electrons correlates with the flux of soft x-ray radiation observed with the use of an x-ray streak camera.
Elaboration of 3-frame complex interferometry for optimization studies of capacitor-coil optical magnetic field generators
- Autoři: Pisarczyk, T., Santos, J.J., Dudzak, R., Kálal, M., Krupka, M., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D.,
- Publikace: Journal of Instrumentation. 2019, 14 ISSN 1748-0221.
- Rok: 2019
- DOI: 10.1088/1748-0221/14/11/C11024
- Odkaz: https://doi.org/10.1088/1748-0221/14/11/C11024
- Pracoviště: Katedra fyziky
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Anotace:
Recently developed three-frame complex-interferometry system driven by a Ti:Sa laser with 40 fs pulse has been installed at the PALS (Prague Asterix Laser System) laser facility. This unique diagnostic allows for the first time to perform simultaneous measurements of B-field in the coil region of the capacitor-coil targets (CCT) and the self-generated B-field (SMF) of the diode plasma in between the CCT-plates. CCT were irradiated by the PALS iodine laser (lambda = 1315 nm) with energy in the range 250–500 J and pulse duration of 350 ps at full width at half maximum. The operation of this diagnostic system and methodologies for quantitative data analysis are presented in this study, including: (i) obtaining information about the induction of the magnetic field in the CCT coil based on measurements of the Faraday effect in the TGG (Terbium Gallium Garnet) paramagnetic crystal at the coil vicinity and (ii) determining magnetic field and current density distributions in the capacitor region of the CCT by analysis of the complex interferograms. The preliminary measurements confirmed the high potential of the reported setup for optimization studies of CCT targets.
Evolution of a Pinch Column During the Acceleration of Fast Electrons and Deuterons in a Plasma-Focus Discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, J., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Skladnik-Sadowska, E., Szymaszek, A., Tomaszewsi, K., Zaloga, D., Zielinska, E.
- Publikace: IEEE Transactions on Plasma Science. 2019, 47(1), 339-345. ISSN 0093-3813.
- Rok: 2019
- DOI: 10.1109/TPS.2018.2874288
- Odkaz: https://doi.org/10.1109/TPS.2018.2874288
- Pracoviště: Katedra fyziky
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Anotace:
Plasma in a pinch column, as produced by a plasma-focus discharge at the deuterium filling and the current intensity reaching 1 MA, was investigated at the total neutron yield reaching about 1010 per discharge. The use was made of neutron diagnostics, laser interferometry, soft X-ray measurements, optical emission spectroscopy, magnetic probes, as well as electron and ion measurements with the temporal, spatial, and energetic resolutions. The detailed studies showed the ordered toroidal, helical, and plasmoidal structures which could contain currents with poloidal and toroidal components and their associated magnetic fields. Their spontaneous transformations were explained by changes in a topology of magnetic field lines due to magnetic reconnections. A nonthermal acceleration of fast electrons and ions (producing hard X-rays and fusion neutrons, respectively) corresponded to: 1) the formation of plasmoids in the pinch column and 2) a decay of pinch constrictions and secondary plasmoids during the evolution of instabilities. A filamentary structure of the current flow could explain the high energy density and fast transformations of the magnetic energy into kinetic energy of electron and ion beams (reaching energy of hundreds of kiloelectronvolt). This paper summarizes the results obtained with the PF-1000 facility in 2009–2017, and describes the internal transformations in a dense plasma column during the evolution of MHD instabilities.
Evolution of the Pinched Column During Hard X-ray and Neutron Emission in a Dense Plasma Focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Zielinska, E., Skladnik-Sadowska, E., Szymaszek, A., Tomaszewski, K., Zaloga, D.
- Publikace: Journal of Fusion Energy. 2019, 38(3-4), 490-498. ISSN 0164-0313.
- Rok: 2019
- DOI: 10.1007/s10894-018-0194-x
- Odkaz: https://doi.org/10.1007/s10894-018-0194-x
- Pracoviště: Katedra fyziky
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Anotace:
The paper summarizes important results of the recent experimental studies performed on the plasma-focus PF-1000 facility operated in Warsaw, Poland, mainly with the pure deuterium filling. Attention is focused on the evolution of toroidal and plasmoidal self-organized structures formed by internal closed currents inside the dense plasma column. The production of hard x-rays and neutrons corresponds with the formation and decay of plasmoids, in which charged particles can be accelerated effectively to high energies, during a release of the magnetic energy from current filaments of high energy density. It is noticed that the studies of laboratory fusion and cosmic plasmas deal with similar problems, e.g., the fast release of the magnetic energy in a form of high-energy charged particle beams.
Features of fast deuterons emitted from plasma focus discharges
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, J., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kwiatkowski, R., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Skladnik-Sadowska, E., Szymaszek, A., Tomaszewski, K., Zaloga, D., Zielinska, E.
- Publikace: PHYSICS OF PLASMAS. 2019, 26 032702-1-032702-10. ISSN 1070-664X.
- Rok: 2019
- DOI: 10.1063/1.5080974
- Odkaz: https://doi.org/10.1063/1.5080974
- Pracoviště: Katedra fyziky
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Anotace:
This paper presents the discussion concerning the characteristics of the fast deuterons which have energy above 30 keV and are recorded during high-current plasma-focus (PF) discharges, by means of PM-355 plastic track-detectors placed inside ion pinhole cameras. The fast deuterons evoke D-D fusion reactions, mainly by a beam-target mechanism. The distribution of the magnetic field, which influences the trajectories of the recorded deuterons, is discussed. It is found that the fast deuterons are produced in various local sources and their motion is strongly influenced by a circular symmetry of the local magnetic field, which increases their radial shift with a decrease in their energy. The sources of these deuterons are probably located inside the plasmoids and in some local regions of the ring-shaped plasma structures. These ring-structures can be formed outside the dense pinch column, up to a radius of 5 cm. Global magnetic fields, associated with the total current flow in the PF discharge, have a weaker influence. The observed radial shift of the recorded fast deuterons is interpreted as a result of their deflection by magnetic fields which have opposite orientations of the azimuthal components, associated with the currents flowing in directions towards and from the applied ion detectors. The local sources of the recorded fast deuterons correspond to filamentary structures, in which the stored magnetic energy (having the local high density) can be released in induced electric fields accelerating the deuterons during the magnetic reconnections.
Influence of an external additional magnetic field on the formation of a plasma column in a dense plasma focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kwiatkowski, R., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D., Skladnik-Sadowska, E., Szymaszek, A., Tomaszewski, K., Zaloga, D., Zielinska, E.
- Publikace: PHYSICS OF PLASMAS. 2019, 26 ISSN 1070-664X.
- Rok: 2019
- DOI: 10.1063/1.5094568
- Odkaz: https://doi.org/10.1063/1.5094568
- Pracoviště: Katedra fyziky
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Anotace:
This paper concerns the evolution of internal structures and the neutron production in plasma-focus discharges performed in the presence of a permanent magnet (placed inside the anode front) and within a residual magnetic field (after the removal of this magnet). The initial magnetic field generated by this magnet prevented: (i) the effective compression of a dense pinch column, (ii) the formation of plasma organized structures, and (iii) the evolution of plasma instabilities. The experimental results have shown an increase in the initial magnetic field due to a magnetic dynamo effect in the presence of the permanent magnet, as well as in a series of shots performed after its removal. It was observed that the appearance of plasmoidal structures is necessary for the emission of fusion neutrons. A characteristic quasicylindrical plasma layer of the radius corresponding to the plasma lobule tops, which might be identified with a ring region of the acceleration of fast deuterons, was also observed.
Initial conditions in the hawk dense plasma focus
- Autoři: Engelbrecht, J.T., Schumer, J.W., Jackson, S.L., Mamonau, A.A., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D.,
- Publikace: 2019 IEEE Pulsed Power & Plasma Science (PPPS). Piscataway: Institute of Electrical and Electronics Engineers, 2019. ISSN 2158-4915. ISBN 9781538679692.
- Rok: 2019
- DOI: 10.1109/PPPS34859.2019.9009625
- Odkaz: https://doi.org/10.1109/PPPS34859.2019.9009625
- Pracoviště: Katedra fyziky
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Anotace:
The 670 kA Hawk pulsed power generator at NRL has been configured as a fast (1.2 μs rise time), high inductance (607 nH) driver for a dynamic dense plasma focus (DPF) load in order to create a testbed for the study of charged particle acceleration mechanisms in imploding plasmas. The current pulse is initiated in a deuterium plasma injected radially by three Marshall guns. This plasma is accelerated through a coaxial region, and pinches onto neutral deuterium injected axially by a gas-puff valve. Promising experimental results along with recent improvements to the Marshall gun design have prompted efforts to better characterize the density profiles produced by the guns. A multichannel heterodyne interferometer focused into a ribbon beam is used to provide time-resolved measurements of the Marshall gun plasma density, allowing parameters to be tuned and mass distributions to be established for a wide range of initial conditions. These interferometric measurements are used in establishing a standard operating condition for the experiment in a high neutron yield regime.
Target return current in low-intensity laser target interaction
- Autoři: Krasa, J., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D.,
- Publikace: Proc. SPIE 11035, Optics Damage and Materials Processing by EUV/X-ray Radiation VII. Bellingham (stát Washington): SPIE, 2019. Proceedings of SPIE. vol. 11035. ISSN 1996-756X. ISBN 978-1-5106-2737-6.
- Rok: 2019
- DOI: 10.1117/12.2522511
- Odkaz: https://doi.org/10.1117/12.2522511
- Pracoviště: Katedra fyziky
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Anotace:
Laser-target interaction experiments demonstrated that the return target current, j(TC)(t), which neutralizes the target charge appearing when the fastest electrons escape the plasma, is one of principal characteristics of the laser-matter interaction. j(TC)(t) flowing between the target and the ground is emerging just when the laser intensity exceeds the threshold intensity of the plasma formation. The experimental determination of the number of escaped electrons is primarily based on precise target current observations.
Axial compression of plasma structures in a plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, M.J., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2018, 25(6), ISSN 1070-664X.
- Rok: 2018
- DOI: 10.1063/1.5033997
- Odkaz: https://doi.org/10.1063/1.5033997
- Pracoviště: Katedra fyziky
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Anotace:
The paper describes the behaviour of plasma within a MA plasma-focus with a novel electrode configuration, in which the anode and anti-anode were both equipped with conical tips. This configuration was applied to test the possibility of reducing the pinch axial dimensions during the radial compression of a current sheath. It made it possible to strengthen a dense plasma jet near the anode end, which ejected plasma into a bigger plasmoidal structure formed in the central pinch region. It did not allow forming an opposite anti-anode jet and stopped the axial motion of this structure. In plasma focus discharges with the deuterium filling, the decay of the anode jet and the corresponding plasmoid evolution were accompanied by the fusion-neutron production. Some results obtained with this configuration have also supported the hypothesis of the acceleration of fast electrons and ions at a release of the magnetic energy during magnetic reconnections in the organized dense plasma structures.
Characterization of fast deuterons involved in the production of fusion neutrons in a dense plasma focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Sadowski, M.J., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2018, 25 ISSN 1070-664X.
- Rok: 2018
- DOI: 10.1063/1.5012021
- Odkaz: https://doi.org/10.1063/1.5012021
- Pracoviště: Katedra fyziky
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Anotace:
This paper considers regions of a fast deuteron production in a correlation with an evolution of ordered structures inside a pinch column of a mega-ampere plasma focus discharge. Ion pinhole cameras equipped with plastic PM-355 track-detectors recorded fast deuterons escaping in the downstream and other directions (up to 60 to the z-axis). Time-integrated ion images made it possible to estimate sources of the deuteron acceleration at the known magnetic field and deuteron energy values. The images of the fast deuterons emitted in the solid angle ranging from 0 to 4 showed two forms: central spots and circular images. The spots of 1–2 cm in diameter were produced by deuterons from the central pinch regions. The circular-shaped images of a radius above 3 cm (or their parts) were formed by deuterons from the region surrounding the dense pinch column. The ion pinhole cameras placed at angles above 20 to the z-axis recorded the ion spots only, and the ring-images were missing. The central region of the deuteron acceleration could be associated mainly with plasmoids, and the circular images could be connected with ring-shaped regions of the radius corresponding to tops of the plasma lobules outside the dense pinch column. The deuteron tracks forming ring-shaped images of a smaller (0.5–1) cm radius could be produced by deflections of the fast deuterons, which were caused by a magnetic field inside the dense pinch column.
EMP characterization at PALS on solid-target experiments
- Autoři: Consoli, F., De Angelis, R., De Marco, M., Krása, J., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Margarone, D., prof. Ing. Daniel Klír, Ph.D., Dudzak, R.
- Publikace: Plasma Physics and Controlled Fusion. 2018, 60(10), ISSN 0741-3335.
- Rok: 2018
- DOI: 10.1088/1361-6587/aad709
- Odkaz: https://doi.org/10.1088/1361-6587/aad709
- Pracoviště: Katedra fyziky
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Anotace:
We describe the characterization of electromagnetic pulses (EMPs) in experiments on solid targets at PALS laser facility in Prague, for energy up to 600 J and intensity up to 10(16)W cm(-2) at focus. Measurements of EMPs have been performed by different conductive probes placed inside and outside the experimental chamber. We show results for different targets and probe configurations, and illustrate effects of spurious direct coupling of these transient fields with the read-out apparatus, which are important for high-energy and high-intensity laser-plasma experiments. The related countermeasures are described and demonstrated to be very effective for improving the signal-to-noise ratio, at expenses of measured bandwidths. They allowed us to detect the EMP components due to the intense neutralization currents flowing through the target holder, and those possibly due to wakefields associated with emitted charged particles, which resulted in these experiments to be of the same order of magnitude. It is the first time both discharge current and associated EMP are effectively measured in the same nanosecond-scale experiment, where this EMP contribution is effectively detected by conductive probes. A remarkable agreement was obtained from comparison of the detected EMP profile with measured neutralization current. We also show the results achieved by means of electromagnetic simulations of fields in the modeled experimental chamber, in particular in the regions where the probes were actually placed during the experiments, and compare them with measured signals. It appears that conductive probes have limitations for the measurement of the high-frequency components of the EMP fields. The illustrated results are of primary importance for the hot topic of EMP characterization and minimization in plants for inertial-confinement-fusion (NIF, LMJ, PETAL) as well as for laser-plasma acceleration (PETAL, ELI, Apollon...).
Investigation of Magnetic Fields in Z-Pinches via Multi-MeV Proton Deflectometry
- Autoři: Ing. Vojtěch Munzar, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc., Kravárik, J., Ing. Karel Řezáč, Ph.D.,
- Publikace: IEEE Transactions on Plasma Science. 2018, 46(11), 3891-3900. ISSN 0093-3813.
- Rok: 2018
- DOI: 10.1109/TPS.2018.2874207
- Odkaz: https://doi.org/10.1109/TPS.2018.2874207
- Pracoviště: Katedra fyziky
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Anotace:
Proton deflectometry is a promising way for mapping electric and magnetic fields in high-density and high-temperature plasmas, where an application of the classical methods (B-dot probes, Faraday rotation, and Zeeman splitting) is limited. It is based on the detection of a multi-MeV proton beam deflected in examined B-fields. In the past years, it has been successfully utilized in laser-generated plasmas for E-field and B-field measurements. Using our numerical code, we investigate the capabilities of proton deflectometry as a diagnostic method of MA Z-pinches. We simulate proton trajectories propagating through typical Z-pinch B-fields in two fundamental experimental setups (radial and axial) in order to study synthetic images (deflectograms). We demonstrate where proton deflectometry might be beneficial for the Z-pinch research. We explain a formation of the key features of deflectograms, which give us information about a profile and strength of the Z-pinch B-fields. We introduce a BL parameter, denoting an effective B-field averaged along the deflected proton orbit and show its importance for the proton deflectometry.
Ion acceleration mechanism in mega-ampere gas-puff z-pinches
- Autoři: prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Hyhlík, T., Kravárik, J., Ing. Vojtěch Munzar, Ph.D., Šíla, O., Stodůlka, J.
- Publikace: New Journal of Physics. 2018, 20 ISSN 1367-2630.
- Rok: 2018
- DOI: 10.1088/1367-2630/aac545
- Odkaz: https://doi.org/10.1088/1367-2630/aac545
- Pracoviště: Katedra fyziky
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Anotace:
Acceleration of high energy ions was observed in z-pinches and dense plasma foci as early as the 1950s. Even though many theories have been suggested, the ion acceleration mechanism remains a source of controversy. Recently, the experiments on the GIT-12 generator demonstrated acceleration of ions up to 30 MeV from a deuterium gas-puff z-pinch. High deuteron energies enable us to obtain unique information about spatial, spectral and temporal properties of accelerated ions. In particular, the off-axis ion emission from concentric circles of a similar to 1 cm diameter and the radial lines in an ion beam profile are germane for the discussion of acceleration mechanisms. The acceleration of 30 MeV deuterons can be explained by the fast increase of an impedance with a sub-nanosecond e-folding time. The high (> 10 Omega) impedance is attributed to a space-charge limited flow after the effective ejection of plasmas from m = 0 constrictions. Detailed knowledge of the ion acceleration mechanism is used with a neutron-producing catcher to increase neutron yields above 10^13 at a current. of. 2.7 MA.
Magnetized plasma implosion in a snail target driven by a moderate intensity laser pulse
- Autoři: Pisarczyk, T., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D., prof. RNDr. Pavel Kubeš, CSc.,
- Publikace: Scientific Reports. 2018, 8 ISSN 2045-2322.
- Rok: 2018
- DOI: 10.1038/s41598-018-36176-8
- Odkaz: https://doi.org/10.1038/s41598-018-36176-8
- Pracoviště: Katedra fyziky
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Anotace:
Optical generation of compact magnetized plasma structures is studied in the moderate intensity domain. A sub-ns laser beam irradiated snail-shaped targets with the intensity of about 10(16) W/cm(2). With a neat optical diagnostics, a sub-megagauss magnetized plasmoid is traced inside the target. On the observed hydrodynamic time scale, the hot plasma formation achieves a theta-pinch-like density and magnetic field distribution, which implodes into the target interior. This simple and elegant plasma magnetization scheme in the moderate-intensity domain is of particular interest for fundamental astrophysical-related studies and for development of future technologies.
Multi probes measurements at the PALS Facility Research Centre during high intense laser pulse interactions with various target materials
- Autoři: De Marco, M., Krása, J., Ing. Jakub Cikhardt, Ph.D., Consoli, F., De Angelis, R., Pfeifer, M., Krůs, M., Dostál, J., Margarone, D., Picciotto, A., Velyhan, A., prof. Ing. Daniel Klír, Ph.D., Dudžák, R., Limpouch, J., Korn, G.
- Publikace: Plasma Physics by Laser and Applications (PPLA 2017). Les Ulis: EDP Sciences, 2018. EPJ Web of Conferences. vol. 167. ISSN 2101-6275.
- Rok: 2018
- DOI: 10.1051/epjconf/201816703009
- Odkaz: https://doi.org/10.1051/epjconf/201816703009
- Pracoviště: Katedra fyziky
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Anotace:
During the interaction of high intense laser pulse with solid target, a large amount of hot electrons is produced and a giant Electromagnetic Pulse (EMP) is generated due to the current flowing into the system target-target holder, as well as due to the escaping charged particles in vacuum. EMP production for different target materials is investigated inside and outside the target chamber, using monopole antenna, super wide-band microstrip antenna and Moebius antenna. The EMP consists in a fast transient magnetic field lasting hundreds of nanosecond with frequencies ranging from MHz to tens of GHz. Measurements of magnetic field and return target current in the range of kA were carried out by an inductive target probe (Cikhardt J. et al. Rev. Sci. Instrum. 85 (2014) 103507).
Production of relativistic electrons, MeV deuterons and protons by sub-nanosecond terawatt laser
- Autoři: Krása, J., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D., Buryšková, S.
- Publikace: PHYSICS OF PLASMAS. 2018, 25(11), ISSN 1070-664X.
- Rok: 2018
- DOI: 10.1063/1.5052146
- Odkaz: https://doi.org/10.1063/1.5052146
- Pracoviště: Katedra fyziky
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Anotace:
By the use of various experimental techniques, it is shown that the relativistic electrons, MeV protons, and deuterons are emitted from a 500-mu m thick (CD2)(n) target exposed to I lambda(2) approximate to 5 x 10(16)W cm(-2) mu m(2), which is delivered by the iodine photodissociation laser Prague Asterix Laser System. A parameter reflecting the laser-power efficiency of the proton acceleration is used for comparison of the observed maximum proton energy with data from other experiments. The number of protons and deuterons constituting the backward and forward jets is estimated. Values of maximum proton energies and electron temperatures indicate that the laser intensity should reach a relativistic level through the laser beam self-focusing. The occurrence of electron bunches in front of the irradiated target surface was identified by time resolved femtosecond interferometry. Energy distribution functions of electrons emitted in the both backward and forward directions are analysed and compared. Published by AIP Publishing.
Relativistic effects in plasma produced with sub-nanosecond 3-TW laser
- Autoři: Krása, J., prof. Ing. Daniel Klír, Ph.D., Kaufman, J., Ing. Jakub Cikhardt, Ph.D.,
- Publikace: Europhysics Conference Abstracts vol. 42A. Mulhouse: European Physical Society, 2018. p. 1700-1703. Europhysics Conference Abstracts. vol. 42A. ISBN 978-1-5108-6844-1.
- Rok: 2018
- Pracoviště: Katedra fyziky
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Anotace:
This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. The PALS laser is a near-infrared 3-TW iodine laser designed to deliver irradiance on target of 10^16 Wcm2- in≈300 ps pulses at the wavelength of 1.315 μm. Various foils of 6 - 500 μm in thickness were irradiated with Iλ2 ≈5×1016 W cm^-2 μm2 Under these conditions we have observed relativistic electrons expanding into the vacuum with maximum energy going beyond 4 MeV. The relativistically accelerated forward electrons escaping from the rear target surface were observed with the use of electron energy analysers. The observed electron energy spectra indicate that the applied laser intensity was increased by the thermal and relativistic self-focusing. The application of a unique femtosecond interferometry technique allowed us to observe bunches of thermal electrons occurring in the plasma expanding against the focused laser beam.
Target current: An appropriate parameter for characterizing the dynamics of laser-matter interaction
- Autoři: Krása, J., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Buryšková, S.
- Publikace: Proceedings of SPIE - The International Society for Optical Engineering. Montréal: SPIE, 2018. vol. 11042. ISSN 0277-786X.
- Rok: 2018
- DOI: 10.1117/12.2520177
- Odkaz: https://doi.org/10.1117/12.2520177
- Pracoviště: Katedra fyziky
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Anotace:
A resistive target probes were employed to obtain unique characteristics of the dynamic of the laser-matter interaction through the observation of a return current neutralizing the positive target charge caused by electrons definitely leaving the plasma. Experimental observations show that three phases of the laser-produced plasma are well recognized, i.e. the plasma ignition phase, active plasma phase, and afterglow phase already for the lowest laser intensity at the focal point of 108 Wcm-2 . Then, at higher intensities the first two phases strongly dominate and the target current reaches a value of 10 kA. A throughput of plasma barrier for the fastest electrons leaving the plasma is defined, and its value is experimentally estimated. We also present key experiments proving that the duration of the electrical charge on the target is much longer than the duration of the laser-plasma interaction for the entire intensity range.
Electromagnetic pulse (EMP) radiation by laser interaction with a solid H-2 ribbon
- Autoři: De Marco, M., Krasa, J., Ing. Jakub Cikhardt, Ph.D., Velyhan, A., Limpouch, J.
- Publikace: PHYSICS OF PLASMAS. 2017, 24(8), ISSN 1070-664X.
- Rok: 2017
- DOI: 10.1063/1.4995475
- Odkaz: https://doi.org/10.1063/1.4995475
- Pracoviště: Katedra fyziky
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Anotace:
The electromagnetic pulses (EMPs) generated during the interaction of a focused 1.315-mu m sub-nanosecond laser pulse with a solid hydrogen ribbon were measured. The strength and temporal characteristics of EMPs were found to be dependent on the target density. If a low density target is ionized during the interaction with the laser, and the plasma does not physically touch the target holder, the EMP is weaker in strength and shorter in time duration. It is shown that during the H-2 target experiment, the EMP does not strongly affect the response of fast electronic devices. The measurements of the EMP were carried out by Rohde&Schwarz B-Probes, particularly sensitive in the frequency range from 30MHz and 1 GHz. Numerical simulations of resonant frequencies of the target chamber used in the experiment at the Prague Asterix Laser System kJ-class laser facility elucidate the peaked structure of EMP frequency spectra in the GHz domain. Published by AIP Publishing.
Experimental research of neutron yield and spectrum from deuterium gas-puff z-pinch on the GIT-12 generator at current above 2 MA
- Autoři: Cherdizov, R.K., Fursov, F.I., Kokshenev, V.A., Kurmaev, N.E., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D.,
- Publikace: Journal of Physics: Conference Series. Bristol: Institute of Physics Publishing Dirac House, Temple Back Bristol, BS1 6BE, 2017. Conference Series. vol. 898. ISSN 1742-6588.
- Rok: 2017
- DOI: 10.1088/1742-6596/830/1/012017
- Odkaz: https://doi.org/10.1088/1742-6596/830/1/012017
- Pracoviště: Katedra fyziky
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Anotace:
The Z-pinch experiments with deuterium gas-puff surrounded by an outer plasma shell were carried out on the GIT-12 generator (Tomsk, Russia) at currents of 2 MA. The plasma shell consisting of hydrogen and carbon ions was formed by 48 plasma guns. The deuterium gas-puff was created by a fast electromagnetic valve. This configuration provides an efficient mode of the neutron production in DD reaction, and the neutron yield reaches a value above 10^12 neutrons per shot. Neutron diagnostics included scintillation TOF detectors for determination of the neutron energy spectrum, bubble detectors BD-PND, a silver activation detector, and several activation samples for determination of the neutron yield analysed by a Sodium Iodide (NaI) and a high-purity Germanium (HPGe) detectors. Using this neutron diagnostic complex, we measured the total neutron yield and amount of high-energy neutrons.
Filamentation in the pinched column of the dense plasma focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D.,
- Publikace: PHYSICS OF PLASMAS. 2017, 24(3), ISSN 1070-664X.
- Rok: 2017
- DOI: 10.1063/1.4978558
- Odkaz: https://doi.org/10.1063/1.4978558
- Pracoviště: Katedra fyziky
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Anotace:
The paper describes the filamentary structure observed in the high-energy ultraviolet radiation for discharges performed at the hydrogen- or deuterium-filling and at the puffing of hydrogen, deuterium or helium, in a mega-ampere dense plasma-focus facility. The lifetime of this structure overcomes 50ns. These filaments connect the surface of a pinched column with internal plasmoids formed at different combinations of filling and puffing gases and they should transport some current and plasma. During all the investigated deuterium shots, the fusion-produced neutrons were recorded. Therefore, deuterons should be present in the region of their acceleration, independent of the applied puffing of the gas. Simultaneously with the observed filaments, inside the dense plasma column small plasma-balls of mm-dimensions were observed, which had a similar lifetime (longer than the relaxation time) and quasi-stationary positions in the discharge volume. The observed filaments and balls might be a manifestation of the (i) discrete spatial structure of the current flowing through and around the dense plasma column and (ii) transport of the plasma from external layers to the central region. Their formation and visualization were easier due to the application of air admixtures in the puffed gas. Published by AIP Publishing.
Increase in the neutron yield from a dense plasma-focus experiment performed with a conical tip placed in the centre of the anode end
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Zielinska, E., Sadowski, M., Szymaszek, A., Tomaszewski, K., Zaloga, D.
- Publikace: PHYSICS OF PLASMAS. 2017, 24 ISSN 1070-664X.
- Rok: 2017
- DOI: 10.1063/1.4994097
- Odkaz: https://doi.org/10.1063/1.4994097
- Pracoviště: Katedra fyziky
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Anotace:
The paper describes the evolution of self-organized structures inside a pinched plasma column during the phase of the effective production of fusion neutrons, as observed in the mega-ampere plasma focus experiment performed with a conical tip placed in the centre of the anode face. In a comparison with the plane anode face configuration, the described anode shape facilitated transformations in the pinch column during the neutron production and increased the neutron yield several times. Simultaneously, it decreased the minimal diameter and the length of the pinched column, and it depressed the first neutron pulse. It also induced shorter pulses of X-rays and neutrons, which enabled the determination of a temporal difference between the emission of electron and deuteron beams. The fast electrons were produced mainly during a disruption of the pinch constriction, while the fast deuterons – during the formation and explosion of plasmoids. The paper also presents the temporal evolution of a current distribution in the plasmoid during the neutron production, as well as the appearance and stable positions of current filaments traces upon the surface of the conical anode tip.
Kinetic magnetization by fast electrons in laser-produced plasmas at sub-relativistic intensities
- Autoři: Pisarczyk, T., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc.,
- Publikace: PHYSICS OF PLASMAS. 2017, 24(10), ISSN 1070-664X.
- Rok: 2017
- DOI: 10.1063/1.4995044
- Odkaz: https://doi.org/10.1063/1.4995044
- Pracoviště: Katedra fyziky
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Anotace:
The problem of spontaneous magnetic field generation with nanosecond laser pulses raises a series of fundamental questions, including the intrinsic magnetization mechanisms in laser-driven plasmas and the understanding of charge-discharge processes in the irradiated target. These two issues are tightly bound as the charge-discharge processes are defined by the currents, which have in turn a feedback by magnetic fields in the plasma. Using direct polaro-interferometric measurements and theoretical analysis, we show that at parameters related to the PALS laser system (1.315 mu m, 350 ps, and 10(16) W/cm(2)), fast electrons play a decisive role in the generation of magnetic fields in the laser-driven plasma. Spatial distributions of electric currents were calculated from the measured magnetic field and plasma density distributions. The obtained results revealed the characteristics of strong currents observed in capacitor-coil magnetic generation schemes and open a new approach to fundamental studies related to magnetized plasmas.
Neutron Spectrum Measured by Activation Diagnostics in Deuterium Gas-Puff Experiments on the 3 MA GIT-12 Z-Pinch
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Shishlov, A.V., Cherdizov, R.K., Ing. Balžima Cikhardtová, Dudkin, G.N., Fursov, F.I., Kokshenev, V.A., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Kurmaev, N.E., Labetsky, A.Yu., Padalko, V.N., Ratakhin, N.A., Šíla, O., Turek, K., Varlachev, V.A.
- Publikace: IEEE Transactions on Plasma Science. 2017, 45(12), 3209-3217. ISSN 0093-3813.
- Rok: 2017
- DOI: 10.1109/TPS.2017.2763641
- Odkaz: https://doi.org/10.1109/TPS.2017.2763641
- Pracoviště: Katedra fyziky
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Anotace:
A set of neutron diagnostics including scintillation time-of-flight detectors, bubble detectors, and several kinds of threshold nuclear activation samples is used to obtain information about the yield and spectrum of the neutrons produced by a deuterium gas-puff z-pinch. The experiments are performed at a current of about 3 MA on the GIT-12 generator at the Institute of High Current Electronics of the Siberian Branch of Russian Academy of Sciences in Tomsk. The average neutron yield in the experiments in 2016 was 2.3 x 10¹² neutrons per single shot. Using the data obtained with the help of neutron activation diagnostics, the time-of-flight detectors have been absolutely calibrated and the broad energy spectrum of the produced neutrons was evaluated. By the calculations presented in this paper, due to the multi-MeV energies of deuterons generated in the pinch, up to 15% of the total neutron yield could be produced by nuclear reactions of deuterons with a stainless steel vacuum chamber and aluminum components of the diagnostic apparatus inside the chamber.
Phases of plasma produced with nanosecond laser
- Autoři: Krása, J., De Marco, M., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Velyhan, A., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: EPS 2017: 44th European Physical Society Conference on Plasma Physics (EPS). Mulhouse: EPS, 2017. ISBN 9781510849303.
- Rok: 2017
- Pracoviště: Katedra fyziky
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Anotace:
Recent experimental studies have shown that the current balancing the charge occurred on a target irradiated with a laser can be used as a basic parameter for characterization of laser ablation. The time-resolved target current indicates the occurrence of various phases of the laser-produced plasma. During the first plasma phase defined by the duration of laser-target interaction, the time derivative of the target current matches the time-resolved laser intensity. The second phase of the laser-produced plasma starts after termination of the laser-matter interaction. For the entire duration of this active phase, the plasma surviving on the target surface emits transient electromagnetic radiation (EMP), X-ray radiation, and slow ions. This surface plasma causes the target charging balanced by a return target current on a time scale of 100 ns. Then the target holder acts as a probe, the signal of which can indicate a residual plasma persisting inside the target chamber on a time scale of microseconds.
Spectral and temporal characteristics of target current and electromagnetic pulse induced by nanosecond laser ablation
- Autoři: Krasa, J., De Marco, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Limpouch, J.
- Publikace: Plasma Physics and Controlled Fusion. 2017, 59(6), ISSN 0741-3335.
- Rok: 2017
- DOI: 10.1088/1361-6587/aa6805
- Odkaz: https://doi.org/10.1088/1361-6587/aa6805
- Pracoviště: Katedra fyziky
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Anotace:
The current balancing the target charging and the emission of transient electromagnetic pulses (EMP) driven by the interaction of a focused 1.315 mu m iodine 300 ps PALS laser with metallic and plastic targets were measured with the use of inductive probes. It is experimentally proven that the duration of return target currents and EMPs is much longer than the duration of laser-target interaction. The laser-produced plasma is active after the laser-target interaction. During this phase, the target acts as a virtual cathode and the plasma-target interface expands. A double exponential function is used in order to obtain the temporal characteristics of EMP. The rise time of EMPs fluctuates in the range up to a few tens of nanoseconds. Frequency spectra of EMP and target currents are modified by resonant frequencies of the interaction chamber.
Target current: a useful parameter for characterizing laser ablation
- Autoři: Krása, J., Giuffreda, E., Delle Side, D., Nassisi, V., prof. Ing. Daniel Klír, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: Laser and Particle Beams. 2017, 35(1), 170-176. ISSN 0263-0346.
- Rok: 2017
- DOI: 10.1017/S0263034617000040
- Odkaz: https://doi.org/10.1017/S0263034617000040
- Pracoviště: Katedra fyziky
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Anotace:
A current flowing between the ground and target exposed to the nanosecond laser radiation is analyzed to complete characteristics of laser ablation. Three phases of the target current are distinguished. During the ignition phase, the electron emission is driven by the laser pulse and the positive charge generated on the target is balanced by electrons coming from the ground through the target holder. At post-pulse times, a peaked waveform of the target current is typical for the active phase of the plasma and can give information on the material composition of the ablated surface layers. The afterglow phase is determined by a current of electrons flowing from the target to the ground. Experiment shows that the time-resolved target current is very sensitive to the actual composition of the surface layer of irradiated target and laser parameters.
Transformation of the ordered internal structures during the acceleration of fast charged particles in a dense plasma focus
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Zielinska, E., Sadowski, J. M., Szymaszek, A., Tomaszewski, K., Zaloga, D.
- Publikace: PHYSICS OF PLASMAS. 2017, 24(7), ISSN 1070-664X.
- Rok: 2017
- DOI: 10.1063/1.4991384
- Odkaz: https://doi.org/10.1063/1.4991384
- Pracoviště: Katedra fyziky
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Anotace:
The paper concerns important differences in the evolution of plasma column structures during the production of fusion neutrons in the first and subsequent neutron pulses, as observed for plasma focus discharges performed with the deuterium filling. The first neutron pulse, of a more isotropic distribution, is usually produced during the formation of the first big plasmoid. The next neutron pulses can be generated by the fast deuterons moving dominantly in the downstream direction, at the instants of a disruption of the pinch constriction, when other plasmoids are formed during the constriction evolution. In both cases, the fusion neutrons are produced by a beam-target mechanism, and the acceleration of fast electron- and deuteron-beams can be interpreted by transformation and decay of the magnetic field associated with a filamentary structure of the current flow in the plasmoid.
Comprehensive investigation of laser energy transport to a massive planar targets with femtosecond polaro-interferometry
- Autoři: Pisarczyk, T., Gus'kov, S.Yu., Chodukowski, T., Dostal, J., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc.,
- Publikace: 43rd EPS Conference on Plasma Physics. Haague: European Geophysical Society, 2016. Europhysics Conference Abstracts. vol. 40A. ISBN 978-1-5108-2947-3.
- Rok: 2016
- Pracoviště: Katedra fyziky
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Anotace:
The experiments were realized on Prague Asterix Laser System (PALS) using the first harmonic of the iodine laser beam with the energy in range of 100- 500 J and the pulse duration of 350 ps. The plasma was created by the irradiation of the bare and plastic coated Cu massive planar targets using both the linear and the circular polarized laser beam which was focused to the minimum focal spot radius of RL=50 um. The primary goal of the current project is to understand the interrelation of spontaneous magnetic field (SMF) creation and fast electron generation in laser plasma produced from planar targets. Two-channel polarointerferometer and the crater volume measurements were applied as the main diagnostics to investigate SMF and efficiency of laser energy transfer to the target. The differences in the fast electron production due to the polarization of the laser beam were monitored by 2D imaging of the Cu K-alpha emission source in the irradiated target. The measured distributions of the SMF during the interaction of the laser pulse with the ablative plasma clearly show that the SMF amplitude is higher in the case of the linearly polarized beam. The data on the efficiency of laser energy transport into the massive target was concluded using the ratio of measured values of total number of thermal electrons of ablated plasma and crater volume. Slightly higher fast electron emission was observed at the circular polarization of the laser beam incident on both bare and plastic coated Cu targets. As an additional diagnostic, the measurements of the total current flowing through the target were carried out by means of the current probe and the found values were compared with results from the SMF measurements.
Deuterium z-pinch as a powerful source of multi-MeV ions and neutrons for advanced applications
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A. V., Kokshenev, V. A., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Kravárik, J., Šíla, O.
- Publikace: PHYSICS OF PLASMAS. 2016, 23(3), ISSN 1070-664X.
- Rok: 2016
- DOI: 10.1063/1.4942944
- Odkaz: https://doi.org/10.1063/1.4942944
- Pracoviště: Katedra fyziky
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Anotace:
A novel configuration of a deuterium z-pinch has been used to generate a nanosecond pulse of fast ions and neutrons. At a 3 MA current, the peak neutron yield of (3.6 +/- 0.5) x 10(12) was emitted within 20 ns implying the production rate of 10 20 neutrons/s. High neutron yields resulted from the magnetization of MeV deuterons inside plasmas. Whereas deuterons were trapped in the radial direction, a lot of fast ions escaped the z-pinch along the z-axis. A large number of >25MeV ions were emitted into a 250 mrad cone. The cut-off energy of broad energy spectra of hydrogen ions approached 40 MeV. The total number of >1 MeV and >25 MeV deuterons were 10(16) and 10(13), respectively. Utilizing these ions offers a real possibility of various applications, including the increase of neutron yields or the production of short-lived isotopes in samples placed in ion paths. On the basis of our experiments with various samples, we concluded that a single shot would have been sufficient to obtain GBq positron activity of 13 N isotopes via the C-12(d, n)(13) N reaction. Furthermore, the first z-pinch generated neutron radiograph produced by approximate to 20 ns pulses is presented in this paper. (C) 2016 AIP Publishing LLC.
Evolution of the small ball-like structures in the plasma focus discharge
- Autoři: Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Cikhardt, Ph.D., Paduch, M., Kravárik, J., Ing. Karel Řezáč, Ph.D., Kortánek, J.
- Publikace: NUKLEONIKA. 2016, 61(2), 155-159. ISSN 0029-5922.
- Rok: 2016
- DOI: 10.1515/nuka-2016-0027
- Odkaz: https://doi.org/10.1515/nuka-2016-0027
- Pracoviště: Katedra fyziky
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Anotace:
The experiments were carried out in the PF-1000 plasma-focus device at the maximum current reaching about 2 MA, at the deuterium or neon filling and with deuterium injected from a gas-puff nozzle placed on the axis of the anode face. Ball-like structures of diameters of 1-12 mm were identified in interferometric and XUV pinhole camera frames. We made the statistical description of their parameters. A lifetime of the ball-like structures was in the range from 30 to 210 ns, and in some cases even more. These structures appeared mostly at the surface of the imploding plasma shell and they did not change their position in relation to the anode end. During the evolution of these structures, interferometric fringes were observed near the surfaces of the structures only, and their internal parts were initially chaotic (without noticeable) fringes. Subsequently the number of interferometric fringes increased (the internal 'chaotic' area was filled with fringes too) and later on it decreased. The radii of the ball-like structures were mostly increasing during their existence. The maximum electron density reached the value of 10(24) to 10(25) m(-3). The ball-like structures decayed by absorption inside the expanded pinch column and/or gradually expired in rare plasma outside of the dense plasma column.
Experiments and simulations on the possibility of radiative contraction/collapse in the PF-1000 plasma focus
- Autoři: Akel, M., Ing. Jakub Cikhardt, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Kunze, H.-J., Lee, S., Paduch, M., Saw, S. H.
- Publikace: NUKLEONIKA. 2016, 61(2), 145-148. ISSN 0029-5922.
- Rok: 2016
- DOI: 10.1515/nuka-2016-0025
- Odkaz: https://doi.org/10.1515/nuka-2016-0025
- Pracoviště: Katedra fyziky
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Anotace:
Experimental studies of discharges in the plasma focus facility with neon fi lling and respective numerical simulations employing the radiative Lee code are reported. The pinch currents exceed the Pease-Braginskii current, which indicates that radiative losses are larger than heating and that contraction of the formed plasma should occur. Both of these effects were indeed observed. Parallel numerical simulations were crucial for the identifi cation of such an effect.
Generation of fast neutrons through deuteron acceleration at the PALS laser facility
- Autoři: Krasa, J., prof. Ing. Daniel Klír, Ph.D., Velyhan, A., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D.,
- Publikace: Journal of Instrumentation. 2016, 11(3), ISSN 1748-0221.
- Rok: 2016
- DOI: 10.1088/1748-0221/11/03/C03050
- Odkaz: https://doi.org/10.1088/1748-0221/11/03/C03050
- Pracoviště: Katedra fyziky
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Anotace:
Recent experiments at the laser facility PALS focused on the laser driven fusion of deuterons are reviewed. They benefit of high reaction cross-sections and of a high number of multi-MeV deuterons from thick CD2 targets irradiated by intensity of 3x10(16) W cm(2). In the reported experiments fast fusion neutrons with energy up to 16 MeV were produced through Li-7(d, n)Be-8 and B-11(d, n)C-12 reactions in a pitcher-catcher target configuration. When using a large area CD2 foil as a secondary catcher target the total maximum neutron yield from the H-2(d, n)He-3 reaction increased by a factor of about 5, from 4x10(8) to 2x10(9). This result reveals that most of the deuterons having enough kinetic energy to enter a fusion reaction are emitted from the primary target into vacuum.
Influence of the Al wire placed in the anode axis on the transformation of the deuterium plasma column in the plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Zielinska, E., Zaloga, D., Sadowski, M. J., Tomaszewski, K.
- Publikace: PHYSICS OF PLASMAS. 2016, 23 ISSN 1070-664X.
- Rok: 2016
- DOI: 10.1063/1.4953569
- Odkaz: https://doi.org/10.1063/1.4953569
- Pracoviště: Katedra fyziky
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Anotace:
In this paper, we describe the influence of an Al wire of 270 lm in diameter placed along the anode axis on the transformation of the deuterium pinch column in a megaampere (MA) plasma focus device. The evolution of the pinched column and of the wire corona was investigated by means of the multiframe interferometry, neutron and X-ray diagnostics. The wire corona did not influence considerably on the evolution of dense plasma structures and neutron production, but it increased the plasma density and consequently, the currents around its surface. The distribution of the closed internal currents (ranging hundreds of kA) and associated magnetic fields amounting to 5 T were also estimated in the dense plasma column and in plasmoidal structures at the near-equilibrium state. The description is based on the balance of the plasma pressure and the pressure of the internal poloidal and toroidal current components compressed by the external pinched column. The dominant number of fusion deuterium-deuterium (D-D) neutrons is produced during the evolution of instabilities, when theuninterrupted wire corona (containing deuterium) connects the dense structures of the pinch, and it did not allow the formation of a constriction of the sub-millimeter diameter.
Interferometry and x-ray diagnostics of pinched helium plasma in a dense plasma focus with an Al-wire on the axis
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Kortánek, J., Zielíinska, E., Sadowski, J. M., Tomaszewski, K.
- Publikace: PHYSICS OF PLASMAS. 2016, 23 ISSN 1070-664X.
- Rok: 2016
- DOI: 10.1063/1.4968227
- Odkaz: https://doi.org/10.1063/1.4968227
- Pracoviště: Katedra fyziky
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Anotace:
The paper describes the evolution of the ordered dense toroidal- and plasmoidal-like structures in a pinch column and the hard X-ray emission from mega-ampere dense plasma-focus discharges performed at the helium (He) filling. Some shots were carried out with an Al-wire of 270 lm in diameter, which was placed along the z-axis in the front of the anode face. The evolution of the considered structures was investigated by means of a multi-frame laser interferometer system as well as the X-ray diagnostics, and it was compared with their evolution observed earlier at the deuterium (D2) filling. In He-plasma, the ions had a higher mass and Z-number, and at the same initial filling pressure, the velocity of plasma transformations was decreased, but the stability of the investigated structures, as well as the self-generated azimuthal current component and the soft X-ray radiation were increased. The distribution of the plasma electron density (determined from the interferometric images) made it possible to estimate closed currents during the quasi-stationary phases. It was found that the internal toroidal- and plasmoidal-currents reached the level of hundreds of kA. The plasma corona around the Al-wire (penetrating through the internal structures) impeded the formation of a small diameter of the pinch constriction, but it did not prevent the production of fast electron beams with energies above 100 keV, similar to those observed at the D2-filling.
Magnetic field induced by laser-driven target current
- Autoři: Krasa, J., Ing. Jakub Cikhardt, Ph.D., De Marco, M., prof. Ing. Daniel Klír, Ph.D., Velyhan, A., Ing. Karel Řezáč, Ph.D.,
- Publikace: 43rd EPS Conference on Plasma Physics. Haague: European Geophysical Society, 2016. Europhysics Conference Abstracts. vol. 40A. ISBN 978-1-5108-2947-3.
- Rok: 2016
- Pracoviště: Katedra fyziky
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Anotace:
This contribution deals with direct observation of a transient magnetic field induced by a current flowing through the target holder to balance the target charging caused by intense laser radiation delivered by the 3 TW, 300 ps laser system PALS. Both the target and its holder fixed to the interaction chamber react to the target ablation as an electrical circuit, which emits electromagnetic pulses in the megahertz to gigahertz domain. For this reason the interaction chamber is considered as a resonant cavity in which different modes of EM field oscillate for hundreds of nanoseconds until EM waves are completely lost. We present an inductive target probe developed by Cikhardt et al. Rev. Sci. Instrum. 85 (2014) 103507, allowing the direct observation of the transient target current. Since the applied inductive target probe is resistive against the interfering electromagnetic pulse (EMP) occurred inside the interaction chamber where the charged particles are accelerated, the relationship between the magnetic part of the EMP elsewhere inside and outside the interaction chamber and the magnetic field induced by the neutralization target current can be obtained. Frequency analysis indicates a multimode frequency distribution of EMP spectra which arises as a mixture of large number of modes.
Measurement of electromagnetic pulses generated during interactions of high power lasers with solid targets
- Autoři: De Marco, M., Krasa, J., Ing. Jakub Cikhardt, Ph.D., Pfeifer, M., Limpouch, J.
- Publikace: Journal of Instrumentation. 2016, 11(6), ISSN 1748-0221.
- Rok: 2016
- DOI: 10.1088/1748-0221/11/06/C06004
- Odkaz: https://doi.org/10.1088/1748-0221/11/06/C06004
- Pracoviště: Katedra fyziky
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Anotace:
A target irradiated with a high power laser pulse, blows off a large amount of charge and as a consequence the target itself becomes a generator of electromagnetic pulses (EMP) owing to high return current flowing to the ground through the target holder. The first measurement of the magnetic field induced by the neutralizing current reaching a value of a few kA was performed with the use of an inductive target probe at the PALS Laser Facility (Cikhardt et al. Rev. Sci. Instrum. 85 (2014) 103507). A full description of EMP generation should contain information on the spatial distribution and temporal variation of the electromagnetic field inside and outside of the interaction chamber. For this reason, we consider the interaction chamber as a resonant cavity in which different modes of EMP oscillate for hundreds of nanoseconds, until the EMP is transmitted outside through the glass windows and EM waves are attenuated. Since the experimental determination of the electromagnetic field distribution is limited by the number of employed antennas, a mapping of the electromagnetic field has to be integrated with numerical simulations. Thus, this work reports on a detailed numerical mapping of the electromagnetic field inside the interaction chamber at the PALS Laser Facility (covering a frequency spectrum from 100MHz to 3 GHz) using the commercial code COMSOL Multiphysics 5.2. Moreover we carried out a comparison of the EMP generated in the parallelepiped-like interaction chamber used in the Vulcan Petawatt Laser Facility at the Rutherford Appleton Laboratory, against that produced in the spherical interaction chamber of PALS.
Proton Acceleration Driven by a Nanosecond Laser from a Cryogenic Thin Solid-Hydrogen Ribbon
- Autoři: Margarone, D., Velyhan, A., Dostál, J., Ullschmied, J., Perin, J.P., Chatain, D., Garcia, S., Bonnay, P., Pisarczyk, T., Dudzak, R., Rosinski, M., Krása, J., Giuffrida, L., Prokůpek, J., Scuderi, V., Pšikal, J., Kuchařík, M., De Marco, M., Ing. Jakub Cikhardt, Ph.D., Krouský, E., Kalinowska, Z., Chodukowski, T., Cirrone, G.A.P., Korn, G.
- Publikace: Physical Review X. 2016, 6(4), ISSN 2160-3308.
- Rok: 2016
- DOI: 10.1103/PhysRevX.6.041030
- Odkaz: https://doi.org/10.1103/PhysRevX.6.041030
- Pracoviště: Katedra fyziky
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Anotace:
A high-power pulsed laser is focused onto a solid-hydrogen target to accelerate forward a collimated stream of protons in the range 0.1–1 MeV, carrying a very high energy of about 30 J (∼5% laser-ion conversion efficiency) and extremely large charge of about ∼0.1 mC per laser pulse. This result is achieved for the first time through the combination of a sophisticated target system (H2 thin ribbon) operating at cryogenic temperature (∼10 K) and a very hot H plasma (∼300 keV “hot electron” temperature) generated by a subnanosecond laser with an intensity of ∼3×1016 W/cm2. Both the H plasma and the accelerated proton beam are fully characterized by in situ and ex situ diagnostics. Results obtained using the ELISE (experiments on laser interaction with solid hydrogen) H2 target delivery system at PALS (Prague) kJ-class laser facility are presented and discussed along with potential multidisciplinary applications.
The evolution of the plasmoidal structure in the pinched column in plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Ing. Balžima Cikhardtová, Kortánek, J., Zielinska, E
- Publikace: Plasma Physics and Controlled Fusion. 2016, 56 ISSN 0741-3335.
- Rok: 2016
- DOI: 10.1088/0741-3335/58/4/045005
- Odkaz: https://doi.org/10.1088/0741-3335/58/4/045005
- Pracoviště: Katedra fyziky
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Anotace:
In this paper, a description is provided of the evolution of the dense spherical-like structures— plasmoids—formed in the pinched column of the dense plasma focus at the current of 1 MA at the final phase of implosion of the deuterium plasma sheath and at the phase of evolution of instabilities both at the time of HXR and neutron production. At the stratification of the plasma column, the plasma injected to the dense structures from the axially neighboring regions forms small turbulences which increase first the toroidal structures, and finally generates a nonchaotic current plasmoidal structure with central maximal density. This spontaneous evolution supports the hypothesis of the spheromak-like model of the plasmoid and its sub-millimeter analogy, high-energy spot. These spots, also called nodules formed in the filamentary structure of the current can be a source of the energy capable of accelerating the fast charged particles.
The influence of the nitrogen admixture on the evolution of a deuterium pinch column
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Balžima Cikhardtová, Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Kortánek, J., Zielinska, E., Sadowski, J. M., Tomaszewski, K.
- Publikace: PHYSICS OF PLASMAS. 2016, 23 ISSN 1070-664X.
- Rok: 2016
- DOI: 10.1063/1.4960825
- Odkaz: https://doi.org/10.1063/1.4960825
- Pracoviště: Katedra fyziky
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Anotace:
The application of a mixture of nitrogen and deuterium for the gas-puffing along the anode axis in deuterium plasma-focus discharges, as carried out at megaampere-level currents, enabled observations of the filamentary structure, and the decrease in the transformation velocity of the plasma column to be performed. It made possible to investigate the instability evolution during the production of hard X-rays and fast neutrons in more detail. The constriction of a plasma column transforms itself during the final phase of the compression into one or more small dense plasmoid-like structures which are separated by narrow necks. During the next phase, these structures start to decay by an expansion, in which a part of the plasma volume maintains its compactness. This evolution is explained by an increase and later decrease in the internal poloidal current component by reconnections of the associated magnetic lines, which are responsible for the acceleration of electron and ion beams.
Efficiency of ablative plasma energy transfer into a massive aluminum target using different atomic number ablators
- Autoři: Kasperczuk, A., Pisarczyk, T., Chodukowski, T., Kalinowska, Z., Stepniewski, W., Jach, K., Swierczynski, R., Renner, O., Smid, M., Ullschmied, J., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Krousky, E., Pfeifer, M., Skala, J.
- Publikace: Laser and Particle Beams. 2015, 33(3), 379-386. ISSN 0263-0346.
- Rok: 2015
- DOI: 10.1017/S0263034615000452
- Odkaz: https://doi.org/10.1017/S0263034615000452
- Pracoviště: Katedra fyziky
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Anotace:
This paper aims at investigation of efficiency of an ablative plasma energy transfer into a massive aluminum target using different atomic number ablators. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5-73) were used. The experiment was carried out at the iodine Prague Asterix Laser System. The laser provided a 250 ps pulse with energy of 130 J at the third harmonic frequency (lambda(3) = 0.438 mu m). To study the plasma stream configurations a four-frame X-ray pinhole camera was used. The electron temperature of the plasma in the near-surface target region was measured by means of an X-ray spectroscopy. The efficiency of the plasma energy transport to the target was determined via the crater volume measurement using the crater replica technique. The experimental results were compared with two-dimensional numerical simulations where the plasma dynamics was based on the one-fluid, two temperature model, including radiation transport in diffusive approximation and ionization kinetics. It was shown that the plasma expansion geometry plays an important role in the ablative plasma energy transfer into the target.
Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Kokshenev, V., prof. RNDr. Pavel Kubeš, CSc., Labetsky, A., Ing. Karel Řezáč, Ph.D., Cherzidov, R., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Dudkin, G., Fursov, F., Garapatsky, A., Kovalchuk, B., Kravárik, J., Kurmaev, N., Orcikova, H., Padalko, V., Ratakhin, N., Šíla, O., Turek, K., Varlachev, V.
- Publikace: Plasma Physics and Controlled Fusion. 2015, 57(4), ISSN 0741-3335.
- Rok: 2015
- DOI: 10.1088/0741-3335/57/4/044005
- Odkaz: https://doi.org/10.1088/0741-3335/57/4/044005
- Pracoviště: Katedra fyziky
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Anotace:
Z-pinch experiments with deuterium gas puffs have been carried out on the GIT-12 generator at 3 MA currents. Recently, a novel configuration of a deuterium gas-puff z-pinch was used to accelerate deuterons and to generate fast neutrons. In order to form a homogeneous, uniformly conducting layer at a large initial radius, an inner deuterium gas puff was surrounded by an outer hollow cylindrical plasma shell. The plasma shell consisting of hydrogen and carbon ions was formed at the diameter of 350 mm by 48 plasma guns. A linear mass of the plasma shell was about 5 ug/cm whereas a total linear mass of deuterium gas in single or double shell gas puffs was about 100 mu g/cm. The implosion lasted 700 ns and seemed to be stable up to a 5 mm radius. During stagnation, m = 0 instabilities became more pronounced. When a disruption of necks occurred, the plasma impedance reached 0.4 Omega and high energy (>2 MeV) bremsstrahlung radiation together with high energy deuterons were produced. Maximum neutron energies of 33 MeV were observed by axial time-of-flight detectors. The observed neutron spectra could be explained by a suprathermal distribution of deuterons with a high energy tail. Neutron yields reached 3.6x10(12) at a 2.7 MA current. A high neutron production efficiency of 6x10(7) neutrons per one joule of plasma energy resulted from the generation of high energy deuterons and from their magnetization inside plasmas.
Efficient neutron production from sub-nanosecond laser pulse accelerating deuterons on target front side
- Autoři: prof. Ing. Daniel Klír, Ph.D., Krasa, J., Ing. Jakub Cikhardt, Ph.D., Dudzak, R., Krousky, E., Pfeifer, M., Ing. Karel Řezáč, Ph.D., Šíla, O., Skala, J., Ullschmied, J., Velyhan, A.
- Publikace: PHYSICS OF PLASMAS. 2015, 22(9), ISSN 1070-664X.
- Rok: 2015
- DOI: 10.1063/1.4931460
- Odkaz: https://doi.org/10.1063/1.4931460
- Pracoviště: Katedra fyziky
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Anotace:
Neutron-producing experiments have been carried out on the Prague Asterix Laser System. At the fundamental wavelength of 1.315 μm, the laser pulse of a 600 J energy and 300 ps duration was focused on a thick deuterated-polyethylene target. A more detailed analysis of neutron time-of-flight signals showed that a significant fraction of neutron yields was produced both by the 2H(d,n)3He reaction and by other neutron-producing reactions. Neutron energies together with delayed neutron and gamma emission showed that MeV deuterons escaped from a laser-produced plasma and interacted ≈50 ns later with a borosilicate blast-shield glass.
Electromagnetic pulses produced by expanding laser-produced Au plasma
- Autoři: DE Marco, M., Ing. Jakub Cikhardt, Ph.D., Krása, J., Velyhan, A., Pfeifer, M., Krouský, E., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Limpouch, J., Margarone, D., Ullschmied, J.
- Publikace: NUKLEONIKA. 2015, 60(2), 239-243. ISSN 0029-5922.
- Rok: 2015
- DOI: 10.1515/nuka-2015-0043
- Odkaz: https://doi.org/10.1515/nuka-2015-0043
- Pracoviště: Katedra fyziky
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Anotace:
The interaction of an intense laser pulse with a solid target produces large number of fast free electrons. This emission gives rise to two distinct sources of the electromagnetic pulse (EMP): the pulsed return current through the holder of the target and the outflow of electrons into the vacuum. A relation between the characteristics of laser-produced plasma, the target return current and the EMP emission are presented in the case of a massive Au target irradiated with the intensity of up to 3 x 10(16) W/cm(2). The emission of the EMP was recorded using a 12 cm diameter Moebius loop antennas, and the target return current was measured using a new type of inductive target probe (T-probe). The simultaneous use of the inductive target probe and the Moebius loop antenna represents a new useful way of diagnosing the laser-matter interaction, which was employed to distinguish between laser-generated ion sources driven by low and high contrast laser pulses.
Existence of a return direction for plasma escaping from a pinched column in a plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Kortánek, J., Ing. Balžima Cikhardtová, Zielinska, E.
- Publikace: PHYSICS OF PLASMAS. 2015, 22 ISSN 1070-664X.
- Rok: 2015
- DOI: 10.1063/1.4921248
- Odkaz: https://doi.org/10.1063/1.4921248
- Pracoviště: Katedra fyziky
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Anotace:
The use of multi-frame interferometry used on the PF-1000 device with the deuterium filling showed the existence of a return motion of the top of several lobules of the pinched column formed at the pinched plasma column. This phenomenon was observed in the presence of an over-optimal mass in front of the anode, which depressed the intensity of the implosion and the smooth surface of the pinched plasma column. The observed evolution was explored through the use of closed poloidal currents transmitted outside the pinched plasma. This interpretation complements the scenario of the closed currents flowing within the structures inside the pinched column, which has been published recently on the basis of observations from interferometry, neutron, and magnetic probe diagnostics on this device.
Investigation of compression of puffing neon by deuterium current and plasma sheath in plasma focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, Ing. Karel Řezáč, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Kortánek, J., Zielinska, E.
- Publikace: PHYSICS OF PLASMAS. 2015, 22(6), ISSN 1070-664X.
- Rok: 2015
- DOI: 10.1063/1.4922483
- Odkaz: https://doi.org/10.1063/1.4922483
- Pracoviště: Katedra fyziky
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Anotace:
This paper presents the results of the research of the influence of compressed neon, injected by the gas-puff nozzle in front of the anode axis by the deuterium current and plasma sheath on the evolution of the pinch, and neutron production at the current of 2 MA. The intense soft X-ray emission shows the presence of neon in the central region of the pinch. During the implosion and stopping of the plasma sheath, the deuterium plasma penetrates into the internal neon layer. The total neutron yield of 1010–1011 has a similar level as in the pure deuterium shots. The neutron and hard X-ray pulses from fusion D-D reaction are as well emitted both in the phase of the stopping implosion and during the evolution of instabilities at the transformation of plasmoidal structures and constrictions composed in this configuration from both gases. The fast deuterons can be accelerated at the decay of magnetic field of the current filaments in these structures.
MCNP calculations of neutron emission anisotropy caused by the GIT-12 hardware
- Autoři: Šíla, O., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová,
- Publikace: NUKLEONIKA. 2015, 60(2), 323-326. ISSN 0029-5922.
- Rok: 2015
- DOI: 10.1515/nuka-2015-0064
- Odkaz: https://doi.org/10.1515/nuka-2015-0064
- Pracoviště: Katedra fyziky
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Anotace:
The MCNP6 and MCNPX calculations for the GIT-12 device in Tomsk were performed to determine the influence of the gas-puff hardware on the neutron emission anisotropy and the neutron scattering rate. A monoenergetic 2.45 MeV neutron source and F1 and F6 tallies were declared in the simulation input. A comparison between MCNP results and the measured data was made. Differences between MCNPX and MCNP6 output data were investigated. In the experiment, two nTOF scintillation detectors with the Bicron BC-408 scintillator were used to measure the neutron waveform. Four bubble BD-PND detectors were used to estimate the amount of neutrons in different places around the neutron source.
Puffing Deuterium Compressed by a Neon Plasma Sheath at the Initial Poloidal Magnetic Field in Plasma Focus Discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Kravárik, J., Ing. Balžima Cikhardtová, Kortánek, J., Zielinska, E.
- Publikace: IEEE Transactions on Plasma Science. 2015, 43(8), 2532-2538. ISSN 0093-3813.
- Rok: 2015
- DOI: 10.1109/TPS.2015.2431858
- Odkaz: https://doi.org/10.1109/TPS.2015.2431858
- Pracoviště: Katedra fyziky
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Anotace:
This paper presents the results of the experimental study of the influence of the applied poloidal magnetic field on the transformation of the plasma column formed by the compression of (10 ± 3)-μg/cm deuterium injected by the gas-puff nozzle in front of the anode axis by the neon plasma sheath of (50 ± 10) μg/cm at a current of 2 MA. The permanent magnet with an initial induction of 20–40 mT placed inside the anode: 1) increased the diameter of the pinch and of the stagnation; 2) depressed the evolution of instabilities and formation of the dense structures in the column; 3) delayed the dip of the current derivative in time (and start of the hard X-ray and neutron emission) 200–300 ns after the first peak of the soft X-ray emission (and the pinch with a minimal diameter near the anode); and 4) decreased the total neutron yield to 10–20%. These results were interpreted in terms of the increase in the repulsive pressure of the compressed poloidal magnetic field, which ncreases the stabilizing helicity of the discharge current. The transformations are independent of the polarity of the magnet.
Temporal distribution of linear densities of the plasma column in a plasma focus discharge
- Autoři: Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Cikhardt, Ph.D., Paduch, M., Zielinska, E., Kravárik, J., Ing. Karel Řezáč, Ph.D., Kortánek, J., Šíla, O.
- Publikace: NUKLEONIKA. 2015, 60(2), 315-318. ISSN 0029-5922.
- Rok: 2015
- DOI: 10.1515/nuka-2015-0065
- Odkaz: https://doi.org/10.1515/nuka-2015-0065
- Pracoviště: Katedra fyziky
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Anotace:
Experiments were carried out on the PF-1000 plasma focus device, with a deuterium filling and with deuterium puffing from a gas-puff nozzle placed on the axis of the anode face. The current was reaching 2 MA. 15 interferometric frames from one shot were recorded with a Nd:YLF laser and a Mach-Zehnder interferometer, with 10-20 ns delay between the frames. As a result, the temporal and spatial distribution of the linear densities and the radial and axial velocities of the moving of plasma in the dense plasma column could be estimated.
Basic features of electromagnetic pulse generated in a laser-target chamber at 3-TW laser facility PALS
- Autoři: DE Marco, M., Pfeifer, M., Krousky, E., Krasa, J., Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Nassisi, V.
- Publikace: Journal of Physics: Conference Series. 2014, 508(1), ISSN 1742-6588.
- Rok: 2014
- DOI: 10.1088/1742-6596/508/1/012007
- Odkaz: https://doi.org/10.1088/1742-6596/508/1/012007
- Pracoviště: Katedra fyziky
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Anotace:
We describe the radiofrequency emission taking place when 300 ps laser pulses irradiate various solid targets with an intensity of 10(16) W/cm(2). The emission of intense electromagnetic pulses was observed outside the laser target chamber by two loop antennas up to 1 GHz. Electromagnetic pulses can be 800 MHz transients, which decay from a peak electromagnetic field of E-0 congruent to 7 kV/m and H-0 congruent to 15 A/m. The occurrence of these electromagnetic pulses is associated with generation of hard x-rays with photon energies extending beyond 1 MeV. This contribution reports the first observation of this effect at the PALS facility.
Efficient Neutron Production from a Novel Configuration of Deuterium Gas-Puff Z-Pinch
- Autoři: prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kravárik, J., Šíla, O., Shishlov, A., Kovalchuk, B., Ratakhin, N., Kokshenev, V., Labetsky, A., Cherzidov, R., Fursov, F., Kurmaev, N., Dudkin, G., Nechaev, B., Padalko, V., Orcikova, H., Turek, K.
- Publikace: Physical Review Letters. 2014, 112(9), ISSN 0031-9007.
- Rok: 2014
- DOI: 10.1103/PhysRevLett.112.095001
- Odkaz: https://doi.org/10.1103/PhysRevLett.112.095001
- Pracoviště: Katedra fyziky
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Anotace:
A novel configuration of a deuterium z pinch has been used to generate fusion neutrons. Injecting an outer hollow cylindrical plasma shell around an inner deuterium gas puff, neutron yields from DD reactions reached Y-n = (2.9 +/- 0.3) x 10(12) at 700 ns implosion time and 2.7 MA current. Such a neutron yield means a tenfold increase in comparison with previous deuterium gas puff experiments at the same current generator. The increase of beam-target yields was obtained by a larger amount of current assembled on the z-pinch axis, and subsequently by higher induced voltage and higher energies of deuterons. A stack of CR-39 track detectors on the z-pinch axis showed hydrogen ions up to 38 MeV. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial time-of-flight detectors, respectively. The number of DD neutrons per one joule of stored plasma energy approached 5 x 10(7). This implies that deuterium gas puff z pinches belong to the most efficient plasma-based sources of DD neutrons.
Filamentary structure of plasma produced by compression of puffing deuterium by deuterium or neon plasma sheath on plasma-focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Kortánek, J., Ing. Balžima Cikhardtová, Ing. Karel Řezáč, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Zielinska, E.
- Publikace: PHYSICS OF PLASMAS. 2014, 21(21), ISSN 1070-664X.
- Rok: 2014
- DOI: 10.1063/1.4903906
- Odkaz: https://doi.org/10.1063/1.4903906
- Pracoviště: Katedra fyziky
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Anotace:
The present experiments were performed on the PF-1000 plasma focus device at a current of 2 MA with the deuterium injected from the gas-puff placed in the axis of the anode face. The XUV frames showed, in contrast with the interferograms, the fine structure: filaments and spots up to 1mm diameter. In the deuterium filling, the short filaments are registered mainly in the region of the internal plasmoidal structures and their number correlates with the intensity of neutron production. The longer filamentary structure was recorded close to the anode after the constriction decay. The long curve-like filaments with spots were registered in the big bubble formed after the pinch phase in the head of the umbrella shape of the plasma sheath. Filaments can indicate the filamentary structure of the current in the pinch. Together with the filaments, small compact balls a few mm in diameter were registered by both interferometry and XUV frame pictures. They emerge out of the dense column and their life-time can be greater than hundreds of ns.
Generation of high-energy neutrons with the 300-ps-laser system PALS
- Autoři: Krasa, J., prof. Ing. Daniel Klír, Ph.D., Velyhan, A., Krousky, E., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D.,
- Publikace: High Power Laser Science and Engineering. 2014, 2 1-6. ISSN 2095-4719.
- Rok: 2014
- DOI: 10.1017/hpl.2014.25
- Odkaz: https://doi.org/10.1017/hpl.2014.25
- Pracoviště: Katedra fyziky
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Anotace:
The laser system PALS, as a driver of a broad-beam ion source, delivered deuterons which generated neutrons with energies higher than 14 MeV through the Li-7(d, n)Be-8 reaction. Deuterons with sub-MeV energy were accelerated from the front surface of a massive CD2 target in the backward direction with respect to the laser beam vector. Simultaneously, neutrons were emitted from the primary CD2 target and a secondary LiF catcher. The total maximum measured neutron yield from D-2(d, n)(HeLi)-He-3-Li-7(d, n)Be-8,C-12(d, n)N-13 reactions was similar to 3.5(+/- 0.5) x 10(8) neutrons/shot.
Influence of an external magnetic field on the dynamics of a modified plasma focus
- Autoři: Ing. Jakub Cikhardt, Ph.D., Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc., Kravárik, J., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D.,
- Publikace: Physica Scripta. 2014, T161 ISSN 0031-8949.
- Rok: 2014
- DOI: 10.1088/0031-8949/2014/T161/014042
- Odkaz: https://doi.org/10.1088/0031-8949/2014/T161/014042
- Pracoviště: Katedra fyziky
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Anotace:
The stability of a plasma column and the evolution of discharges are strongly dependent on the axial magnetic field. Internal axial and radial components of the magnetic field are formed at high current discharges naturally, but they can be also produced artificially by auxiliary coils or permanent magnets. The PFZ-200 facility was modified for the experiments with an external axial magnetic field. On this facility, an anti-electrode was placed along the z-axis in front of the anode. The auxiliary coils or permanent magnets generating the axial magnetic field were placed inside the anode and anti-electrode. Using micro-channel plate diagnostics, the stability of the plasma column at an axial magnetic field was studied. At the discharges in deuterium gas, the neutron production and the generation of hard x-rays were diagnosed with the scintillation detectors.
Measurement of the Target Current and EMP on Terawatt Laser System PALS
- Autoři: Ing. Jakub Cikhardt, Ph.D., Krása, J., DE Marco, M., Pfeifer, M., Velyhan, A., Krouský, E., Ing. Balžima Cikhardtová, prof. RNDr. Pavel Kubeš, CSc., prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Ullschmied, J., Skála, J.
- Publikace: Kudowa Summer School "Towards Fusion Energy" Programme & Contributions. Warsaw: Institute of Plasma Physics, 2014. p. 89. ISSN 2083-5876.
- Rok: 2014
- Pracoviště: Katedra fyziky
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Anotace:
The experiments are performed at high-power photodissociation iodine laser (1.315 μm, E=<1 kJ, t = 400 ps, I=6x10E16 W/cm2) at thePALSResearchCenterinPrague.During interaction of a focused intensive laser pulse with a solid target fast electrons are escaping and the target becomes charged. This charge can be neutralized by current flowing throw the target holder to the ground. The current with large time derivation, which is related to the laser pulse shape and to the inductance of the grounding circuit, generates a electromagnetic pulse in radio or microwave frequency band. Because the interaction chamber is usually equipped by a glass windows, insulators for galvanic separation, cables and so on, the electromagnetic pulse (EMP) passes out from the interaction chamber. At high-power laser facilities the EMP disturbs electrical signals, causes incorrect work of diagnostics, computers or control equipment. The study of target currents and EMP is important for design of all diagnostic instruments and projects of the large laser systems.
Measurement of the target current by inductive probe during laser interaction on terawatt laser system PALS
- Autoři: Ing. Jakub Cikhardt, Ph.D., Krása, J., DE Marco, M., Pfeifer, M., Velyhan, A., Krouský, E., Ing. Balžima Cikhardtová, prof. Ing. Daniel Klír, Ph.D., Ing. Karel Řezáč, Ph.D., Ullschmied, J., Skála, J., prof. RNDr. Pavel Kubeš, CSc., Kravárik, J.
- Publikace: Review of Scientific Instruments. 2014, 85(10), ISSN 0034-6748.
- Rok: 2014
- DOI: 10.1063/1.4898016
- Odkaz: https://doi.org/10.1063/1.4898016
- Pracoviště: Katedra fyziky
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Anotace:
Measurements of the return-current flowing through a solid target irradiated with the sub-nanosecond kJ-class Prague Asterix Laser System is reported. A new inductive target probe was developed which allows us measuring the target current derivative in a kA/ns range. The dependences of the target current on the laser pulse energy for cooper, graphite, and polyethylene targets are reported. The experiment shows that the target current is proportional to the deposited laser energy and is strongly affected by the shot-to-shot fluctuations. The corresponding maximum target charge exceeded a value of 10 μC. A return-current dependence of the electromagnetic pulse produced by the laser-target interaction is presented.
Neutron production from puffing deuterium in plasma focus device
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., Ing. Jakub Cikhardt, Ph.D., Kortánek, J., Ing. Balžima Cikhardtová, Ing. Karel Řezáč, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Surala, W., Zielinska, E., Scholz, M., Karpinski, L., Karpinski, L.
- Publikace: PHYSICS OF PLASMAS. 2014, 21 ISSN 1070-664X.
- Rok: 2014
- DOI: 10.1063/1.4892551
- Odkaz: https://doi.org/10.1063/1.4892551
- Pracoviště: Katedra fyziky
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Anotace:
The current research has continued on the PF-1000 plasma focus device at the current of 2 MA by comparison of the shots with and without injected deuterium. The increase of the total neutron yield at the level of 1010–1011 per shot was achieved after the compression of about 10 lg/cm of the deuterium from the gas-valve by about 46 lg/cm of the neon or deuterium plasma sheath. It increases five times at the decrease of the puffing deuterium mass to one-half. In shots with neon in the chamber and with puffing deuterium, a considerable decrease was confirmed of the soft X-ray emission in comparison with shots without deuterium injection. This decrease can be explained by the absence of the neon in the region of the compressed and hot plasma. The deuterium plasma from the gas-puff should then be confined in the internal structures both in the phase of implosion as well as during their formation and transformation. In shots with puffing deuterium, the evolution of instabilities in the plasma column was suppressed. The deuterium plasma has a higher conductance and better ability to form expressive and dense plasmoids and to transport the internal current in comparison with neon plasma. Neutrons were produced both at the initial phase of stagnation, as well as at a later time at the evolution of the constrictions and dense plasmoids. VC 2014 AIP Publishing LLC.
Characterization of neutron emission from mega-ampere deuterium gas puff Z-pinch at microsecond implosion times
- Autoři: prof. Ing. Daniel Klír, Ph.D., Shishlov, A., Kokshenev, V., prof. RNDr. Pavel Kubeš, CSc., Labetsky, A., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Fursov, F., Kovalchuk, B., Kravárik, J., Kurmaev, N., Rathakin, N., Šíla, O., Stodůlka, J.
- Publikace: Plasma Physics and Controlled Fusion. 2013, 55(8), ISSN 0741-3335.
- Rok: 2013
- DOI: 10.1088/0741-3335/55/8/085012
- Odkaz: https://doi.org/10.1088/0741-3335/55/8/085012
- Pracoviště: Katedra fyziky
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Anotace:
Experiments with deuterium (D-2) triple shell gas puffs were carried out on the GIT-12 generator at a 3 MA current level and microsecond implosion times. The influence of the mass of deuterium shells on neutron emission times, neutron yields and neutron energy spectra was studied.
Correlation of X-ray emission with interferometry and neutron diagnostics at tungsten anode face and deuterium filling in plasma-focus discharge
- Autoři: prof. RNDr. Pavel Kubeš, CSc., Paduch, M., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kortánek, J., Kowalska-Strzeciwilk, E., Zielinska, E., Scholz, M., Karpinski, L.
- Publikace: Plasma Physics and Controlled Fusion. 2013, 55(55), ISSN 0741-3335.
- Rok: 2013
- DOI: 10.1088/0741-3335/55/11/115005
- Odkaz: https://doi.org/10.1088/0741-3335/55/11/115005
- Pracoviště: Katedra fyziky
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Anotace:
In this paper, the influence of the tungsten evaporated from the anode on neutron production and soft X-ray radiation was studied on the base of X-ray, interferometry and neutron diagnostics performed on the plasma focus PF-1000 device with deuterium as the filling gas at the current of 2 MA and neutron yield above 1010. In the axial center of the anode face the copper circuit plate was substituted with a tungsten one. During the pinch, the tungsten ions evaporated from the anode were transported into the plasma column. The differences in the filters used in the MCP X-frames and PIN detectors enabled separation of the bremsstrahlung emitted by the deuterium plasma from the recombination radiation of the tungsten ions produced in the region of the plasma column near the anode at the time of the evolution of instabilities. In comparison with the copper anode face, the neutron yield decreased to 40 % and the energy of deuterons producing neutrons to 80%.
ESTIMATION OF AMOUNT OF SCATTERED NEUTRONS AT DEVICES PFZ AND GIT-12 BY MCNP SIMULATIONS
- Autoři: Šíla, O., prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D., Kravárik, J.
- Publikace: Acta Polytechnica. 2013, 53(2), 228-232. ISSN 1210-2709.
- Rok: 2013
- Pracoviště: Katedra fyziky
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Anotace:
Our work is dedicated to pinch effect occurring during current discharge in deuterium plasma, and our results are connected with two devices – plasma focus PFZ, situated in the Faculty of Electrical Engineering, CTU, Prague, and Z-pinch GIT-12, which is situated in the Institute of High Current Electronics, Tomsk. During fusion reactions that proceed in plasma during discharge, neutrons are produced. We use neutrons as instrument for plasma diagnostics. Despite of the advantage that neutrons do not interact with electric and magnetic fields inside device, they are inevitably scattered by materials that are placed between their source and probe, and information about plasma from which they come from is distorted. For estimation of rate of neutron scattering we use MCNP code.
Influence of the external magnetic field on the pinch evolution and neutron production in plasma-focus discharge
- Autoři: Paduch, M., Zielinska, E., prof. RNDr. Pavel Kubeš, CSc., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Kortánek, J., Scholz, M., Karpinski, L.
- Publikace: Plasma Physics and Controlled Fusion. 2013, 55(55), ISSN 0741-3335.
- Rok: 2013
- DOI: 10.1088/0741-3335/55/11/115013
- Odkaz: https://doi.org/10.1088/0741-3335/55/11/115013
- Pracoviště: Katedra fyziky
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Anotace:
In this paper, the results of the study of the influence of the applied external axial magnetic field on the dynamics of the pinch and neutron production are presented, following from the measurements using X-ray, interferometry and neutron diagnostics performed on the plasma focus PF-1000 device with deuterium as the filling gas at the current of 2 MA and neutron yield above 1010. The permanent magnets with a magnetic field of a few hundredths of tesla were used both inside the anode body and in front of the end of the dense column. This magnetic field decreases the neutron yield, depresses the implosion velocity and the velocity of the transformations of internal structures, stabilizes the pinch column, increases its axial symmetry and indirectly confirms the existence of internal closed currents inside the pinch structures.
Plastic plasma interaction with plasmas with growing atomic number
- Autoři: Kasperczuk, A., Pisarczyk, T., Chodukowski, T., Kalinowska, Z., Gus'kov, S., Demchenko, N., Ullschmied, J., Krousky, E., Pfeifer, M., Skala, J., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Jakub Cikhardt, Ph.D., Ing. Karel Řezáč, Ph.D., Pisarczyk, P.
- Publikace: Central European Journal of Physics. 2013, 11(5), 575-579. ISSN 1895-1082.
- Rok: 2013
- DOI: 10.2478/s11534-013-0218-0
- Odkaz: https://doi.org/10.2478/s11534-013-0218-0
- Pracoviště: Katedra fyziky
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Anotace:
This paper describes the investigation of the influence of target material atomic number (Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5 - 73), i.e. plastic (CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging.
The Construction Of The Fast Resistive Bolometer For a SXR Measurement On The GIT-12 Facility
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., prof. RNDr. Pavel Kubeš, CSc., Kravárik, J., Ing. Karel Řezáč, Ph.D., Šíla, O., Shishlov, A.V., Labetsky, A.Yu.
- Publikace: Acta Polytechnica. 2013, 53(2), 134-137. ISSN 1210-2709.
- Rok: 2013
- Pracoviště: Katedra fyziky
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Anotace:
A lot of kinds of instruments are used for the SXR measurement at pulsed power facilities, but most of them are difficult to calibrate absolutely. For the determination of the energy of SXR radiated by the discharge on Z-pinches, it is possible to use the bolometer which can be calibrated analytically. The bolometer can be constructed with the sufficient sensitivity and, at the same time, with the time resolution in the order of nanoseconds. This bolometer was designed and constructed for the measurement on the 5MA facility GIT-12 at the Institute of High Current Electronics (IHCE) of the Siberian Branch Russian Academy of Sciences in Tomsk. The experiments on GIT-12 with the neon and deuterium gas-puff load were diagnosed by the copper bolometer with the time resolution of 4 ns and the sensitivity of 12Vcm2 J−1.
Design and construction of the fast bolometer for X-ray measurement on the Z-pinches
- Autoři: Ing. Jakub Cikhardt, Ph.D.,
- Publikace: 16th International Student Conference on Electrical Engineering. Praha: České vysoké učení technické v Praze, Fakulta elektrotechnická, 2012. ISBN 978-80-01-05043-9.
- Rok: 2012
- Pracoviště: Katedra fyziky
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Anotace:
The main advantage of the bolometer is the possibility of achieve flat characteristic of the sensitivity in the wide energy range. But the disadvantage of the bolometer is usually a low sensitivity and at the same good time resolution. The bolometer for the soft X-ray measurement was designed and made for the facility GIT-12 at the Institute of High Current Electronics (IHCE) of the Siberian Branch Russian Academy of Sciences. The 2 m thickness copper stripe was selected as a sensitive element. These parameters enable the enough 35 ns time resolution and the 2 keV upper bound of the photon energy range. The sensitivity of the sensor is depended on the bias current. The power supply for this bolometer is triggered generator of the 10 s long rectangle pulses with current 10 A.
The SXR bolometer design for measurement on the power Z-pinches
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. RNDr. Pavel Kubeš, CSc., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., Ing. Karel Řezáč, Ph.D., Shishlov, A. V., Labetsky, A. Yu., Chaikovsky, S. A.
- Publikace: Eleventh Kudowa Summer School "Towards Fusion Energy" 2012. Warsaw: IPPLM, 2012. pp. 143-146. ISSN 2083-5876.
- Rok: 2012
- Pracoviště: Katedra fyziky
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Anotace:
Design and construction of the high speed SXR pulse bolometer and experiments on the GIT-12 facility at Institute of High Current Electronics (IHCE SB RAN) in Tomsk.
The Noise Reduction of the Measured Signal in Plasma Diagnostics with Adaptive Filtration
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Karpinski, L., Paduch, M., Scholz, M., Zielinska, E.
- Publikace: Towards Fusion Energy 2011. Warsaw: IPPLM, 2011. ISSN 2983-5884.
- Rok: 2011
- Pracoviště: Katedra fyziky
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Anotace:
In the Wiener filtration the measured and reference signals are recorded in the channels of the osciloskops and the reference noise passes through the adaptive filter
Developing of High-Speed Electromagnetic Deuterium Valve for Gas-Puff in Z-Pinch
- Autoři: Ing. Jakub Cikhardt, Ph.D., prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D.,
- Publikace: Workshop 2010. Praha: České vysoké učení technické v Praze, 2010. pp. 24-25. CTU Reports. ISBN 978-80-01-04513-8.
- Rok: 2010
- Pracoviště: Katedra fyziky
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Anotace:
Studies of the mechanism of neutron production in the D(d,n)3He reactions are the main purpose of our experiments. The gas-puff is the most effective load for Z-pinch discharges for neutron generation. The Gas-puff valves for experiments on the S-300 facility in RRC Kurchatov Institute in Moscow have developed since year 2007. Maximum current peak in the S-300 facility is 4 MA. Development of the electromagnetically triggered gas-puff valve began in October 2008. The main experiments with this electromagnetic valve were done in the RRC Kurchatov Institute Moscow in September and October 2009. There were done 11 shots with peak current of 2 MA with 100 ns rise time. The Z-pinch discharges in the gas-puff seems to be the way for achieve high neutron yields.
Efficient production of 100 keV deuterons in deuterium gas puff Z-pinches at 2MA current
- Autoři: prof. Ing. Daniel Klír, Ph.D., Kravárik, J., prof. RNDr. Pavel Kubeš, CSc., Ing. Karel Řezáč, Ph.D., Ing. Jakub Cikhardt, Ph.D., Litseva, E., Hyhlík, T.
- Publikace: Plasma Physics and Controlled Fusion. 2010, 52(6), 065013-1-065013-17. ISSN 0741-3335.
- Rok: 2010
- DOI: 10.1088/0741-3335/52/6/065013
- Odkaz: https://doi.org/10.1088/0741-3335/52/6/065013
- Pracoviště: Katedra fyziky
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Anotace:
Deuterium gas puff experiments were carried out on the S-300 Z-pinch at the Kurchatov Institute in Moscow. Gas puffs imploded onto the axis before a current peak at about 100 ns. Fusion neutrons were generated after the gas puff implosion during global expansion of a plasma column. On the basis of experimental observations, we concluded that a total energy of deuterons accelerated to fusion energies was above 1.5 kJ. It is more than 15% of the energy input into a plasma. Therefore gas puff Z-pinches seem to be not only powerful sources of x-ray radiation but also efficient sources of 100 keV deuterons.