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8Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2019
SIMULATIONS OF HARD X-RAYS GENERATION BY HOT ELECTRONS IN
A SILVER TARGET
O.F. Kostenko
Joint Institute for High Temperatures of the Russian Academy of Sciences, Moscow, Russia,
e-mail: olegkost@ihed.ras.ru
To radiograph substances with a high energy density, use is made of X-rays in the 10 - 100 keV range. Radiographing the dense plasma which is to be produced by heavy ion beams on the FAIR under construction calls for X-rays with photon energies above 100 keV.
In Ref. [1] we determined the hot-electron energy distribution function by modelling the data of bremsstrahlung and Ka radiation measurements for silver targets with no recirculation of hot electrons, which
19 —2
were produced by s-polarised subpicosecond laser pulses of peak intensity 2x10 W cm on the PHELIX laser facility.In the present work, we consider a semi-analytical model of X-ray bremsstrahlung generation in metallic targets with the inclusion of hot electron recirculation [2].The hard X-ray bremsstrahlung and characteristic radiation yields were calculated in relation to the thickness of a silver target.
The effect of hot electron recirculation in thin foils was shown to significantly improve the Ka radiation and bremsstrahlung yields in the 10 — 100 keV photon energy range. By contrast, the bremsstrahlung photon yield in the 0.1 — 1 MeV energy range from 10 — 20 |im thick foils, in which the hot electrons recirculate, corresponds approximately to the photon yield from the rear sides of 1 — 2 mm thick targets, in which the recirculation is insignificant.The laser-to-Ka radiation energy conversion coefficient and the spectral contrast of the Ka radiation with the use of a 10-^m thick silver foil, in which the recirculation is implemented, are consistent with the data obtained on the Titan laser facility [3].When use is made of the specified target, the laser to 0.1 — 1 MeV bremsstrahlung energy conversion efficiency is 4x10-4.As follows from Ref. [4], for such coefficient it is possible to obtain high-quality radiographic images of millimetre-sized lead samples heated by heavy ion beams to a high energy density state.
References
[1] O.F. Kostenko, N.E. Andreev, O.N. Rosmej. 2018Phys. Plasmas 25 (3) 033105.
[2] O.F. Kostenko. 2019 Quantum Electronics 49(3) 216.
[3] B. Westover et al. 2010 Phys. Plasmas 17(8) 082703.
[4] K. Li et al. 2014 Laser Part. Beams 32(4) 631.
