Multi-beam effects in laser-driven proton focusing for proton fast ignition

Proton fast ignition (pFI) is an approach to inertial fusion that separates the stages of fuel compression and heating. In pFI, nanosecond lasers compress the fusion fuel, and picosecond lasers generate a fast proton beam to ignite it. This requires a robust, reliable proton source capable of delivering the small spot sizes (~10 μm), short pulse durations (~10 ps), and high energies (~10 kJ)

Laser-driven proton acceleration from concave targets has been proposed to meet these beam conditions (Patel et al., PRL, 2003), however, multiple laser beams may be needed to achieve the required proton beam energies.

We explore multi-laser beam proton acceleration from concave targets using particle-in-cell simulations with the EPOCH code. We examine how the distribution of laser spots affects proton acceleration and focusing, with attention to the effects of beam overlap. We discuss how our results, based on parameters of our experiment at CSU ALEPH laser (30 J, 40 fs), can be scaled to intermediate energy and pulse duration regime (~1 kJ, ~1 ps).

This work was made possible by funding from the U.S. Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program, supported by the US DOE Contract No. DE-AC02-09CH11466. This work was supported by the Laboratory Directed Research and Development Program of PPPL. The simulations presented in this article were performed on computational resources managed and supported by Princeton Research Computing at Princeton University.