Optimization of laser-nanowire target interaction to increase the proton acceleration efficiency

M. DOZIERES; G. PETROV; P. FORESTIER-COLLEONI; P. CAMPBELL; K. KRUSHELNICK; A. MAKSIMCHUK; C. MCGUFFEY; V. KAYMAK; A. PUKHOV; M. G. CAPELUTO; R. HOLLINGER; S. SHLYAPTSEV; J.J. ROCCA; F. BEG

PLASMA PHYSICS AND CONTROLLED FUSION

IOP PUBLISHING LTD

Lugar: Londres; Año: 2019

0741-3335

We report on improved proton acceleration from the interaction of a short pulse high intensity laser (>1020 Wcm-2) with nano-engineered targets. Planar targets (from 7 to 20 μm) with protruding gold nanowires having different total areal densities, lengths, and diameters, ranging from 3% to 60% of the size of the laser focal spot were used during an experimental campaign at the 3 J, 30 fs HERCULES laser facility. The results show the importance of the average number of nanowires per focal spot, N, on laser energy absorption. We show that theproton acceleration is significantly improved by using 1 nanowires per focal spot. Detailed analysis indicates that 1 nanowire per focal spot optimizes the interaction between laser pulse and nanowires, in which the wings of the pulse pull out electrons from the wires forming a plasma with density that allows for deep penetration of the laser pulse into the array. When moving away from this optimum in both directions, N1, the laser pulse-nanowire coupling is either too weak or unfavorable for obtaining maximum proton energy. Protonspectra are compared to simulations using 2D-3V and 3D Particle-In-Cell (PIC) codes which reproduce the experimental data with a good agreement.