Recombination effects during expansion into vacuum in laser produced Sn plasma

Abstract

The distance over which the charge state distribution evolves during the expansion of laser produced Sn plasma in vacuum is investigated experimentally. This distance is found to be less than 6 cm with a planar target irradiated by a 1.064 μm laser at 8.3×1011 W/cm2 but greater than 60 cm when a 10.6 μm laser at 2.5×1010 W/cm2 is used. The difference is attributed to the laser wavelength dependence of the coronal electron density and the subsequent recombination processes during expansion. Important implications to the extreme ultraviolet x-ray source application are discussed specifically.