Effect of ionization and recombination between excited states on gain of 19.6nm X-ray laser

Abstract

As it is difficult to solve a large number of rate equations including doubly excited states of various ions, block matrix method is expected to dramatically reduce the machine time by dividing the large number of equations into pieces of small units, and solving them one by one, on condition that the ionization and recombination between excited states of ions can be ignored. In this paper, the influence of ionization and recombination between excited states on plasma status was studied, and detailed analysis of its mechanism was made. The effect on gain of Ne-like Ge 19.6nm X-ray laser respectively driven by 1.0ns pulse, 100ps pulse and 5ps pre-pulse and main pulse was studied. The simulation shows that for the 5ps driving pulse case, the ionization and recombination between excited states has relatively large influence, and it can not be ignored and that for the two quasi-stable state cases, in the gain region with electron density less than 5×1020cm－3, the FWHM temporal width of gain increases by～10%, and the FWHM spatial width of gain increases respectively by～13% and ～-23%, and the time the peak gain appears is delayed respectively by～1.4% and ～6.9%, which is tolerable, implying that the block matrix method could be applied in the qualitative modeling of QSS scheme X-ray laser. However, for accurate study, the ionization between the excited states could not be neglected.