Charged-particle acceleration and energy loss in laser-produced plasmas

Spectral measurements have been made of charged fusion products produced in deuterium + helium-3 filled targets irradiated by the OMEGA laser system [ T, R, Boehly et al., Opt. Commun. 133, 495 (1997)]. Comparing the energy sh ifts of four particle types has allowed two distinct physical processes to be probed: Electrostatic acceleration in the low-density corona and energy loss in the high-density target. When the fusion burn occurred during the l aser pulse, particle energy shifts: were dominated by acceleration effects. Using a simple model for the accelerating field region, the time history o f the target electrostatic potential was found and shown to decay to zero s oon after laser irradiation was complete. When the fusion burn occurred aft er the pulse, particle energy shifts were dominated by energy losses in the target, allowing fundamental charged-particle stopping-power predictions t o be tested. The results provide the first experimental verification of the general form of stopping power theories over a wide velocity range. (C) 20 00 American Institute of Physics. [S1070-664X(00)03012-3].