Survey and Optimization of Laser-Driven Ion Beams

Laser-driven ion acceleration mechanisms have been studied in a series of experiments at the Trident laser facility. Access to multiple such mechanisms has been enabled by a variety of laser targets, ranging from nanofoil targets of different materials to foams that provide near-critical-density plasmas. The operative physics has been constrained by an extensive set of diagnostics, including ion spectrometers, electron spectrometers, frequency-resolved optical gating of the reflected and transmitted laser beams, and a transmitted-laser-beam profiler. Ion acceleration has been observed in both the regimes where the laser plasma remains opaque and where it becomes transparent. In some cases a measure of ion-spectral control has been demonstrated, beyond the typical Maxwellian ion distribution. Simulations have been performed to clarify our understanding of the underlying physics. In this presentation, the salient ion-beam results are shown, along with key measurements that identify the dominant acceleration mechanism. The theoretical considerations behind the observed performance optimizations are summarized.