Intense high-contrast femtosecond -shell X-ray source from laser-driven Ar clusters

Chen, L. M.*; Liu, F.*; Wang, W. M.*; Kando, Masaki; Mao, J. Y.*; Zhang, L.*; Ma, J.*; Li, Y. T.*; Bulanov, S. V.; Tajima, Toshiki; Kato, Yoshiaki ; Sheng, Z. M.*; Wei, Z. Y.*; Zhang, J.*

Bright Ar quasimonochromatic -shell X-ray with very little background has been generated using an Ar clustering gas jet target irradiated with a 30 fs ultrahigh-contrast laser, with a measured flux of 2.210 photons/J into 4. This intense X-ray source critically depends on the laser contrast and intensity. The optimization of source output with interaction length is addressed. Simulations point to a nonlinear resonant mechanism of electron heating during the early stage of laser interaction, resulting in enhanced X-ray emission. The X-ray pulse duration is expected to be only 10 fs, opening the possibility for single- shot ultrafast keV X-ray imaging applications.