COLLISIONAL EXCITATION X-RAY LASER EXPERIMENTS IN PLASMAS PRODUCED BY 0.53-MUM AND 0.35-MUM LASER-LIGHT

Recent Ne- and Ni-like X-ray laser experiments carried out at the Centre d'Etudes de Limeil-Valenton (CEL-V) are reviewed. A variety of experiments in Ne-like X-ray lasers were performed; here we discuss measurements of soft X-ray amplification in Ge (Z=32) and Sr (Z=38) plasmas. In Ge plasmas produced by 0.53-μm laser light at an irradiance of 6.0×1013 W/cm2, gains between 2.2-2.5 cm-1 on the 232.2 and 236.2 Å J=2-1 lines and a gain of 1.0 cm-1 on the 196.1 Å J=0-1 line were measured. In addition, gains of 4.4 cm-1 and 4.0 cm-1 have been demonstrated on the J=2-1 transitions at 164.1 and 166.5 Å in Nelike Sr at laser intensities of 1.3×1014 W/cm2. The effects of pumping the Ne-like Se X-ray laser with 0.35-μm laser light have also been investigated; the Se lasing spectra is similar to that obtained with 0.53-μm light. Experiments have also been carried out to optimize the gain of the 50.3 Å Ni-like Yb (Z=70) J=0-1 line. For Yb, no significant increase in gain over that previously reported was seen, but the time history of the Ni-like Yb X-ray laser was measured for the first time. Finally, attempts to extrapolate the Ni-like results to shorter wavelength were made using Ta (Z=73), W (Z=74), and Re (Z=75). No definitive observation of the Ni-like J=0-1 lasing lines was made in these experiments. © 1990 Springer-Verlag.