INTENSE J=0-1 SOFT-X-RAY LASING AT 28.5 NM IN NEON-LIKE CHROMIUM

Intense 3p-3s, J=0-1 soft-x-ray lasing at 28.5 nm in neonlike chromium has been observed experimentally using a compact Nd:glass laser as th e driver. 2.4-cm-long polished chromium slab targets were irradiated w ith up to 100-J/500-ps pulses at the fundamental wavelength of 1.054 m u m. The prepulse technique was applied using a defined prepulse 5 ns before the main purse and with a prepulse-to-main purse energy ratio o f 0.7%. It is demonstrated that a pump energy of similar to 80 J, corr esponding to a pump irradiance of approximately 9 TW/cm(2) is sufficie nt to observe soft-x-ray lasing at 28.5 nm. At a drive laser energy of similar to 90 J a gain coefficient of (2.2+/-0.5) cm(-1) was measured . The one-dimensional space-resolved measurements show that the 28.5-n m laser line is emitted from a 60-mu m-wide (full width at half maximu m) plasma region.