IONIZATION-INDUCED REFRACTION IN RECOMBINATION X-RAY LASERS

Ionization-induced refraction is examined in regimes relevant to recen t and planned recombination x-ray lasing experiments [D. C. Eder et al ., Phys. Plasmas 1, 1744 (1994)]. A model that self-consistently evolv es the laser radiation as it ionizes a neutral gas is presented. The m odel allows for multiple ionization stages and for spatial variations in the neutral gas density appropriate for studying gas jets and laser evaporated gases. The length of highly stripped plasma is calculated in H-like Li and Li-like N systems, where the conditions are appropria te for recombination. It is found that for a given pump power there is always an optimal spot size and focal position with respect to the ga s jet, which minimizes refraction and maximizes the length for which g ain is possible. (C) 1996 American Institute of Physics.