Abstract

The idea of generating inversion and gain by photo-ionization followed by three-body recombination was first stated by Bunkin¹ et al., and further analized by Goodwin and Fill². The application of this scheme for the specific case of a hydrogen-like C VI plasma, exposed to the soft x-ray emission of a titanium-laser-produced plasma was considered in Ref. ³. Necessary conditions for the achievement of inversion are a low plasma temperature (~ 10 eV) , and a high electron density (~ 10¹⁹ cm^–3). Both are required for the establishment of a strong collisional-recombination regime, favouring the cascading of electrons towards the upper excited levels, leaving the lower levels almost unpopulated. Radiative cooling was originally proposed as a means to reach the desired temperature in similar recombination schemes⁴, however posterior work has shown that this regime was not attainable for low-Z materials⁵. In this paper we consider in detail the hypothesis of radiative cooling for the case of C VI pumped by the Ti-plasma.

© 1991 Optical Society of America