Enhancement of X-Ray Generation in a High-Repetition-Rate Laser-Plasma Experiment

An approximate fourfold enhancement of X-ray generation per shot has been observed from a laser plasma after multiple laser shots onto a 2-mm-thick aluminum target produced ablation ("burn-through") over the thickness of the target. A table-top Nd:YAG laser with a pulse energy of 0.5 J, a pulse duration of 170 ps, a wavelength of 1.06 μm, and a 5-Hz repetition rate was utilized. Over multiple shots at an irradiance of 1015 W · cm-2, the peak hot electron temperature remained approximately constant at 6-7.5 ± 0.5 keV, indicating that the increased X-ray yield when the laser irradiates a burnt-through target results from an increase in the total number of hot electrons.