EFFICIENT J=0-1 SOFT-X-RAY LASING IN NEON-LIKE IONS AT PUMP POWERS BELOW 250GW

Experimental investigations on 3p-3s soft-X-ray lasing in neon-like tr ansition metal plasmas using the prepulse technique are reported. Inte nse J=0-1 lasing in neon-like Ti, Cr, Fe, Ni, and Zn at 32.6, 28.5, 25 .5, 23.1, and 21.2 nm, respectively, is observed at pump powers of les s than 250 GW, corresponding to irradiances of less than 12 TW/cm(2). By using a 0.7% prepulse that precedes the main pulse by 5 ns and appl ying a total pump energy of 100J or less, the J = 0-1 lasing is at lea st one order of magnitude higher than the non-lasing background. For t he 32.6-nm line of Ti, the 25.5-nm line of Fe, and the 23.1-nm line of Ni, gain coefficients of (4.2+/-0.4) cm(-1), (3.9+/-0.3) cm(-1), and (3.6 +/- 0.6) cm(-1), respectively, were measured for 2.4-cm-long curv ed targets, resulting in gain-length products of similar to 10. Angle- resolved spectra indicate a beam divergence of 3 mrad (FWHM), typicall y. The space-resolved spectra show that the J = 0-1 lasing lines are e mitted from an approximately 60-mu m-wide (FWHM) plasma region, wherea s the nearby continuum emission is produced in a considerably broader plasma region of similar to 250 mu m. Lasing at 25.5 nm in neon-like i ron was observed at a pump power as low as 180 GW (similar to 9 TW/cm( 2)), with, however, considerable shot-to-shot scatter in the absolute laser output.