EFFECTIVE GAIN AND STARK PROFILE CALCULATIONS IN THE RECOMBINATION SCHEME X-RAY LASERS

Stark profile functions of Al10+ lasing lines in recombining plasmas a re calculated. Due to electron-emitter collisions and dynamic ion micr ofields, 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 broaden ing. Consistently with experiments, an effective gain is derived from intensity of the X-ray beam, versus plasma length. A lowering of the e ffective and the spectral peak gains, with respect to the commonly use d Doppler gain, is noticed. Effective and peak values differ by less t han 13% for transitions at 15.47 nm, and by less than 10% for those at 10.57 nm. Comparison with experimental results is discussed. Calculat ions seem to indicate that there is no gain at 10.57 nm, due to a larg e Stark broadening.