Hard x-ray radiation yield from a dense plasma as a function of the wavelength of the heating ultrashort laser pulse

摘要

The effect of intensity, length, and wavelength of an ultrashort laser pulse on the formation of a hot electron component in a dense laser-produced plasma was first investigated in a single experiment. For a pulse length of 1 ps (or 200 fs, but with an energy contrast ratio of ～20), it was shown that the principal mechanism of generation of hot electrons is the resonance absorption of laser radiation and that the temperature of hot electrons depends on the laser pulse intensity I and the wavelength λ as T_h ～ (Iλ~2)~(1/3). The homogenisation of the nanostructures of porous silicon due to a poor contrast ratio or a long duration (1 ps) of the laser pulse lowers the yield of hard x-ray radiation compared to the case of high-contrast 200-fs pulses.