Radiation pressure acceleration of high-quality ion beams using ultrashort laser pulses

TL;DR

This paper demonstrates that controlling Rayleigh-Taylor-like instabilities in radiation pressure acceleration with ultrashort laser pulses enables the production of high-quality, high-energy ion beams with predictable energy limits, validated by simulations.

Contribution

It identifies the instability growth as a key factor in beam quality and establishes optimal laser parameters for producing high-energy ion beams with consistent energy spread.

Findings

High-energy proton beams of 100-300 MeV achievable with ultrashort pulses.

Beam spectral quality depends on controlling electron heating and instabilities.

Maximum ion energy per nucleon is independent of target and laser parameters under optimal conditions.

Abstract

The generation of compact, high-energy ion beams is one of the most promising applications of intense laser-matter interactions, but the control of the beam spectral quality remains an outstanding challenge. We show that in radiation pressure acceleration of a thin solid target the onset of electron heating is determined by the growth of the Rayleigh-Taylor-like instability at the front surface and must be controlled to produce ion beams with high spectral quality in the light sail regime. The growth rate of the instability imposes an upper limit on the laser pulse duration and intensity to achieve high spectral beam quality and we demonstrate that under this optimal regime, the maximum peak ion beam energy per nucleon is independent of target density, composition, and laser energy (transverse spot size). Our predictions are validated by two- and three-dimensional particle-in-cell simulations, which indicate that for recent and upcoming experimental facilities using ultrashort ($\lesssim 25$ fs) laser pulses it is possible to produce $100 - 300$ MeV proton beams with $\sim 30\%$ energy spread and high laser-to-proton energy conversion efficiency.