超相对论强度激光与薄膜靶作用中0.4nm以下X射线阿秒脉冲的产生

Generation of attosecond X-ray pulse of wavelength below 0.4nm from the interaction of ultra-relativistic intense lasers with thin foil targets

用一维粒子模拟程序对功率密度在1022W/cm2以上的超强激光驱动薄膜靶产生的相对论电子层及其经过汤姆孙散射产生的阿秒X射线进行了研究.结果表明,在超相对论强度范围下增大驱动激光强度,相应减小等离子体密度及厚度可使电子层获得更高纵向动量,使汤姆孙散射光明显向更短波长移动.优化相关参数得到了波长为1.168nm的阿秒脉冲.经过对倍频探测光方案与驱动光以及薄膜靶参数进行综合考虑和优化,得到的X射线相干辐射波长有效减小到0.4nm以下,产生的光子能量达到2keV以上.

By one-dimensional particle-in-cell simulations, the relativistic electron sheets generated by interaction between the ultra- relativistic intense laser pulse with intensity above 1022 W/cm2 and the thin foil target, as well as the attosecond X-ray pulses induced by Thomson backscattering from electron bunch are studied in this paper. The results indicate that increasing the intensity of the driv- ing laser, reducing the density and thickness of foil target corresponding make the longitudinal momentum of the electrons enhanced and the wavelength of X-ray radiation reduced. Attosecond X-ray pulse with wavelength 1.168 nm can be obtained through optimizing correlated parameters. Especially, using probing laser pulse with doubling frequency and optimizing parameters of the drive light and thin film target can make the wavelength of coherent attosecond X-ray radiation reduced obviously, even below 0.4 nm, and the energy of the scattered photons can achieve more than 2 keV.