Laser plasma studies at Soreq using Gaussian and shaped pulses

The 1.06 μm laser system at Soreq has been modified to produced single and double-step flat-topped laser pulses in the nanosecond range using a cavity-dumped Q-switched oscillator and ''pre-lasing''. Shock wave measurements carried out on aluminum targets showed a marked difference between flat-topped and Gaussian-shaped pulses. With the former, shock waves with velocities of 2-3x106 cm/sec were observed while using the latter pulses resulted in no observable shock waves. Calculations carried out with double-step pulses exhibit the phenomenon on two shock collisions which when optimized can lead to compressions of between 30 and 40 and ''stagnation pressures'' on the order of 30 Tpa for impedance-mismatched 2 layer targets. Direct measurements of the target potential and the charged particle currents from laser irradiated aluminum plasma have lead to the suggestion that double layers may be formed in such plasmas and that they can be directly connected to wave instabilities in the plasma. Laser produced spectra of highly ionized Cd, In, Sn and Te atoms have been observed which exhibit unresolved transition arrays or bands (UTA) of the higher ionization states. A theoretical explanation of these arrays has been attempted. (author). 7 refs, 4 figs