Orbital angular momentum enhanced laser absorption and neutron generation

TL;DR

This study demonstrates that using orbital angular momentum in laser beams significantly enhances plasma absorption and neutron production, achieving record neutron yields with lower laser energies.

Contribution

It is the first experimental demonstration of OAM beams boosting laser absorption and neutron generation in plasmas, supported by PIC simulations.

Findings

Record fast-neutron yield of 1.45 million n/sr achieved.

OAM beams with topological charge 5 outperform Gaussian beams in neutron production.

Enhanced plasma wave excitation and resonance absorption observed.

Abstract

We experimentally demonstrate enhanced absorption of near relativistic optical vortex beams in $\mathrm{D_2O}$ plasmas to generate a record fast-neutron yield of $1.45 \times 10^6$ n/s/sr. Beams with a topological charge of 5 were shown to deliver up to a 3.3 times enhancement of fast-neutron yield over a Gaussian focused beam of the same energy but having two orders of magnitude higher intensity. This result was achieved with laser energies of 16 mJ and a pulse duration of 67 fs. The Orbital Angular Momentum (OAM) beam-target interactions in our experiment were also investigated through Particle-in-Cell (PIC) simulations. Electron density rippling resulting in enhanced plasma wave excitation on the critical surface and significantly enhanced resonance absorption is observed.