Maximizing MeV x-ray dose in relativistic laser-solid interactions

TL;DR

This paper investigates how laser pulse parameters influence MeV x-ray production in laser-solid interactions, revealing new electron temperature scaling and the benefits of short, intense pulses for directed x-ray emission.

Contribution

It introduces a new temperature scaling law based on pulse duration and density scale length, and demonstrates how pulse duration affects x-ray beam divergence and energy.

Findings

Superponderomotive electron temperatures depend on pulse duration and density scale length.

Short, high-intensity pulses produce low-divergence, forward-directed MeV x-ray beams.

Optimal pulse parameters enhance x-ray dose and directionality.

Abstract

Bremsstrahlung x-rays generated in laser-solid interactions can be used as light sources for high-energy-density science. We present electron and x-ray spectra from particle-in-cell and Monte Carlo simulations, varying laser pulse intensity and duration at fixed energy of 200$\,$J. Superponderomotive electron temperatures are observed at low intensity; a new temperature scaling is given that depends on pulse duration and density scale length. Short, high-intensity pulses create low-divergence electron beams before self-generated magnetic fields evolve, resulting in more forward-going MeV x-rays.