Superthermal x-ray emission from CO2-laser-produced plasmas

Abstract
The high‐energy continuum x‐ray emission from plasma created by intense (1014 W cm−2) nanosecond 10‐μm laser pulses has been characterized. The temperature of the superthermal electron component deduced from this emission was found to be strongly dependent on focus position, while displaying a weaker dependence on irradiation angle, beam polarization, and target composition. The variation of the hot‐electron temperature as a function of Iλ2 has been examined in detail in a range of Iλ2 from 1015 to 2×1016 W μm2 cm−2 for various target materials and has been found to be in qualitative agreement with the predictions of current theories of hot‐electron production based on resonance absorption.