Observation of high efficiency Betatron radiation from femtosecond petawatt laser irradiated near critical plasmas

TL;DR

This paper demonstrates a highly efficient Betatron x-ray radiation process using petawatt laser irradiation of near critical plasmas, achieving significantly higher energy conversion efficiency than previous methods.

Contribution

It provides the first experimental demonstration of high-efficiency Betatron radiation from petawatt laser-irradiated near critical plasmas, with detailed analysis and simulations.

Findings

Electron beams up to 70 MeV were generated.

Energy conversion efficiency from laser to x-rays reached 1e-4.

Enhanced acceleration observed with sharp plasma density boundaries.

Abstract

We present an experimental demonstration of high conversion efficiency Betatron x-ray radiation from petawatt laser irradiated near critical plasmas. Direct laser acceleration serves as the dominant regime when laser pulse of ~5e20 W/cm2 intensity is focused into plasmas with electron density of 3e20 /cm3. Electron beam with a charge of ~35 nC is accelerated up to a maximum energy of 70 MeV and emit x-rays when oscillating in the laser field. The deduced energy conversion efficiency from laser to x-rays is up to 1e-4, orders of magnitude higher than other betatron regimes. Enhancement of acceleration and radiation with sharp plasma density boundary is also obtained and further interpretated with 2D particle-in-cell simulations.