Bright synchrotron radiation from relativistic self-trapping of a short laser pulse in near-critical density plasma

TL;DR

This paper demonstrates how relativistic self-trapping of short laser pulses in near-critical density plasma can generate bright, high-energy X-ray and gamma-ray radiation with high efficiency, using 3D particle-in-cell simulations.

Contribution

It introduces a regime of relativistic self-trapping in dense plasma that enhances laser energy conversion into high-energy photons, supported by detailed simulation results.

Findings

Generation of 0.1-1 MeV photons with high brightness and low divergence.

Laser energy conversion efficiency up to 10^{-4} for high-energy photons.

Production of billions to trillions of photons with PW-class lasers.

Abstract

In a dense gas plasma a short laser pulse propagates in relativistic self-trapping mode, which enables effective conversion of laser energy to the accelerated electrons. This regime sustains effective loading which maximizes the total charge of the accelerating electrons, that provides a large amount of betatron radiation. The 3D particle-in-cell simulations demonstrate how such regime triggers X-ray generation with 0.1-1 MeV photon energies, low divergence, and high brightness. It is shown that a 135 TW laser can be used to produce $3\times 10^{10}$ photons of $>10$ keV energy and a 1.2 PW laser makes it possible generating about $10^{12}$ photons in the same energy range. The laser-to-gammas energy conversion efficiency is up to $10^{-4}$ for the high-energy photons, $\sim 100$ keV, while the conversion efficiency to the entire keV-range x-rays is estimated to be a few tenths of a percent.