Study of hard x-ray emission from intense femtosecond Ti:sapphire laser–solid target interactions.

Interaction of intense Ti:sapphire laser with solid targets has been studied experimentally by measuring hard x-ray and hot electron generation. Hard x-ray (8–100 keV) emission spectrum and Kα x-ray conversion efficiency (η_K) from plasma have been studied as a function of laser intensity (10¹⁷–10¹⁹ W/cm²), pulse duration (70–400)fs, and laser pulse fluence. For intensity I>1×10¹⁷ W/cm², the Ag η_K increases to reach a maximum value of 2×10^-5 at an intensity I=4×10¹⁸ W/cm². Hot electron temperature (KT_h) and η_K scaling laws have been studied as a function of the laser parameters. A stronger dependence of KT_h and η_K as a function of the laser fluence than on pulse duration or laser intensity has been observed. The contribution of another nonlinear mechanism, besides resonance absorption, to hard x-ray enhancement has been demonstrated via hot electron angular distribution and particle-in-cell simulations. [ABSTRACT FROM AUTHOR]