High-energy quasi-monoenergetic proton beam from micro-tube targets driven by Laguerre–Gaussian lasers

Abstract

High-energy proton beams with low energy spread and angular divergence are highly valuable in various applications, such as proton therapy, ultrafast science, and nuclear physics. Laser-driven ion sources are being explored as a more compact and cost-effective alternative to conventional accelerators. However, producing high-quality proton beams using lasers has been a significant challenge. In this study, we propose a novel approach to achieve high-energy quasi-monoenergetic proton beams by utilizing a Laguerre–Gaussian (LG) laser to irradiate a solid hollow tube target. Our three-dimensional particle-in-cell simulations demonstrate that the LG laser efficiently pulls out and accelerates electrons. As these electrons exit the rear side of the tube, a charge-separation electric field for proton acceleration is self-established. Meanwhile, a considerable part of the electrons are confined to the laser axis by the ponderomotive force of the LG laser, generating a longitudinal bunching field and transverse focusing field. As a result, protons are accelerated and focused in these fields, producing a high- quality proton beam with high energy (247 MeV) and low energy spread (∼2%) using an LG laser with an intensity of $1.9 \times 10^{21}$ W cm ^−2 and a tube target with an electron density of 40 n _c . In comparison to a standard Gaussian laser, the LG laser exhibits superior performance in terms of proton cut-off energy, energy spread, and angular divergence.

Keywords

• ion acceleration
• Laguerre–Gaussian laser
• high-energy monoenergetic proton beam
• electron acceleration