ANGULAR ENERGY-DISTRIBUTION AND TEMPORAL EVOLUTION OF PULSES EMITTED FROM LOW-Z NEON-LIKE J=0-1 X-RAY LASERS

We report a systematic investigation of the angular energy distributio n and temporal evolution of pulses emitted from low-Z neonlike J=0-1 l asers by comparing prepulse-induced lasing in different materials (S, Cl, Ca, Ti, Ni, Cu, and Zn) and at different driving energies in the m ain pulse and the prepulse. It is found that with a main pulse energy of 350+/-35 J and a prepulse energy of 50+/-5 J, the laser peaks about 4 mrad off axis with a divergence of 4.5-7.5 mrad for the low-Z mater ials S, Cl, Ca, Ti, and Ni. Under the same conditions for Cu, Zn, and Ge the laser peaks about 6-7 mrad off axis with a divergence of 5-8.2 mad. The lasing pulse durations range from 146 to 349 ps for Z=30-16 a nd peak at 237-413 ps before the peak of the L-band emission or the J= 2-1 lasing line. The beam deflection and divergence, as well as the pu lse duration are quite insensitive to the energies of the main pulse a nd the prepulse. However, a lower driving main pulse energy brings las ing close to the peak of the L-band emission.