超短强激光与固体薄膜靶作用产生keV相干X射线数值模拟研究

Numerical study on coherent keV x ray generation by the interaction of ultra-short intense lasers with thin solid foils

用一维粒子模拟研究了超短强激光脉冲与两个固体薄膜靶作用产生X射线的一个方案,特别研究了该方案中产生相对论电子层的源靶的厚度和密度分布对产生x射线的能谱、能量转换效率的影响.数值模拟发现当产生高能电子层的源靶的厚度d与产生的x射线的波长λ/4λ_x^2相当或者更小(λ是入射激光波长)时,才能产生准单色的x射线光谱,否则产生的光谱有极大展宽,且最高频率下降很快.另外,当薄膜靶前面存在不均匀预等离子体时,x射线光谱会明显变差.

The scheme of x ray generation by the interaction of ultra-short intense laser puls with two thin solid foils is re-investigated by one-dimensional numerical simulation.Attention is paid particularly to the effects of the thickness and the density distribution of the source target on the frequency spectrum and the conversion efficiency of the produced x ray emission,where the source target provides a relativistic electron layer.When the thickness of the source target is comparable to or smaller than the wavelength of x rayλ/4νx^2 （λis the wavelength of the incident laser）,quasi-monochromatic x ray spectrum can be generated.Otherwise the spectrum will be broadened significantly and the maximum frequency will decrease rapidly.In addition,the presence of inhomogeneous preplasma in front of the foil will induce a similar change of the spectrum.