Hot electron effects on the satellite spectrum of laser-produced plasmas

Abstract

In laser-produced plasmas, the interaction of the intense laser light with plasma electrons can produce high-energy superthermal electrons with energies in the keV range. These hot electrons can influence the level populations which determine spectral line structure. In the present paper, the effect of hot electrons on the X-ray satellite spectrum of laser-produced plasmas is studied. Calculated spectra are compared with experimental observations. Magnesium targets irradiated by three different types of laser pulses are considered. These include, a high-intensity 600 fs Nd-glass laser, a 1 ns Nd-glass laser, and a 2 ns CO 2 laser. The Nd-glass laser experiments were conducted recently at the Los Alamos Trident Facility and the CO 2 data were recorded by MISDC. High-resolution spectra were measured near the He-like resonance line of magnesium. The calculations employ an electron energy distribution which includes a thermal and a hot electron component, as part of a detailed collisional-radiative model. Plasma parameters including electron temperature, density, and hot electron fraction are estimated by choosing best fits to the experimental measurements. The calculations show that hot electrons can cause several anomalous effects. The Li-like jkl, abcd , and qr satellites can show intensities which are generally attributed to electron densities in excess of 10 23 cm -3. In addition, the relative amplitude of the intercombination line can be unusually large even at high electron densities due to enhanced collisional excitation of the 1 s2p 3 P state by hot electrons.