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

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/cm(2) 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 driving 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.