Effective gain and Stark profile calculations in the recombination scheme x-ray lasers
Résumé
Stark profile functions of Al10+ lasing lines in recombining plasmas are calculated. Due to electron-emitter collisions and dynamic ion microfields, the 3d-4f and 3d-5f lines at 10.57 and 15.47 nm, respectively, are broadened by a large amount, compared to thermal Doppler broadening. Consistently with experiments, an effective gain is derived from intensity of the X-ray beam, versus plasma length. A lowering of the effective and the spectral peak gains, with respect to the commonly used Doppler gain, is noticed. Effective and peak values differ by less than 13% for transitions at 15.47 nm, and by less than 10% for those at 10.57 nm. Comparison with experimental results is discussed. Calculations seem to indicate that there is no gain at 10.57 nm, due to a large Stark broadening.