Monoenergetic proton beams accelerated by a radiation pressure driven shock

TL;DR

This paper demonstrates that intense infrared laser interactions with gaseous hydrogen can produce monoenergetic proton beams with low energy spread via radiation pressure driven shock acceleration, offering a promising alternative to traditional ion sources.

Contribution

It introduces a novel method of generating monoenergetic proton beams using radiation pressure acceleration on gaseous targets, achieving small energy spread and high contrast.

Findings

Proton spectra with ~4% energy spread were achieved.

The acceleration is driven by shock from radiation-pressure hole-boring.

First theoretical demonstration of high contrast monoenergetic beams from RPA.

Abstract

High energy ion beams (> MeV) generated by intense laser pulses promise to be viable alternatives to conventional ion beam sources due to their unique properties such as high charge, low emittance, compactness and ease of beam delivery. Typically the acceleration is due to the rapid expansion of a laser heated solid foil, but this usually leads to ion beams with large energy spread. Until now, control of the energy spread has only been achieved at the expense of reduced charge and increased complexity. Radiation pressure acceleration (RPA) provides an alternative route to producing laser-driven monoenergetic ion beams. In this paper, we show the interaction of an intense infrared laser with a gaseous hydrogen target can produce proton spectra of small energy spread (~ 4%), and low background. The scaling of proton energy with the ratio of intensity over density (I/n) indicates that the acceleration is due to the shock generated by radiation-pressure driven hole-boring of the critical surface. These are the first high contrast mononenergetic beams that have been theorised from RPA, and makes them highly desirable for numerous ion beam applications.