Hard x-ray emission in high intensity femtosecond laser - target interaction

Hard x-ray spectra (10 - 100 keV) created in high contrast, 400 fs, laser pulse interaction with solid targets, have been studied for laser intensities in the 1017 - 1019 ampersand hthinsp;W/cm2 range. The target atomic numbers (Z) extended from Z=13 to Z=73. The measured conversion efficiency at Ag Kα emission line was 10-3% at 5x1018 ampersand hthinsp;W/cm2. It has been confirmed that the hot electron temperature increased as (Iλ2)1/3 and the fraction of laser energy in hot electrons follows scaling law of (Iλ2)3/4. copyright 1999 American Institute of Physics