Angular energy distribution and temporal evolution of pulses emitted from low-ZneonlikeJ=0–1 x-ray lasers

We report a systematic investigation of the angular energy distribution and temporal evolution of pulses emitted from low-Z neonlike J=0--1 lasers by comparing prepulse-induced lasing in different materials (S, Cl, Ca, Ti, Ni, Cu, and Zn) and at different driving energies in the main 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 materials 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 mrad. The lasing pulse durations range from 146 to 349 ps for Z=30--16 and 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 pulse duration are quite insensitive to the energies of the main pulse and the prepulse. However, a lower driving main pulse energy brings lasing close to the peak of the L-band emission. {} 1996 The American Physical Society.