Controlling fast electron beam divergence using two laser pulses

TL;DR

This study demonstrates experimentally that using two co-linear laser pulses can guide relativistic electron beams in solid targets, reducing divergence and increasing current density, with potential applications in inertial fusion.

Contribution

First experimental demonstration of guiding relativistic electron beams with two laser pulses creating magnetic fields in solid targets.

Findings

Reduced electron beam divergence by 2.7 times

Increased electron current density by 1.8 times

Optimal conditions include 4-6 ps delay, 10:1 intensity ratio, and 186 J energy

Abstract

This paper describes the first experimental demonstration of the guiding of a relativistic electron beam in a solid target using two co-linear, relativistically intense, picosecond laser pulses. The first pulse creates a magnetic field which guides the higher current fast electron beam generated by the second pulse. The effects of intensity ratio, delay, total energy and intrinsic pre-pulse are examined. Thermal and K{\alpha} imaging showed reduced emission size, increased peak emission and increased total emission at delays of 4 - 6 ps, an intensity ratio of 10 : 1 (second:first) and a total energy of 186 J. In comparison to a single, high contrast shot, the inferred fast electron divergence is reduced by 2.7 times, while the fast electron current density is increased by a factor of 1.8. The enhancements are reproduced with modelling and are shown to be due to the self-generation of magnetic fields. Such a scheme could be of considerable benefit to fast ignition inertial fusion.