Energetic spin-polarized proton beams from two-stage coherent acceleration in laser-driven plasma

TL;DR

This paper introduces a laser-driven plasma scheme that produces highly energetic, highly polarized proton beams by overcoming polarization loss through a two-stage coherent acceleration process, confirmed by 3D simulations.

Contribution

The study presents a novel two-stage coherent acceleration method using laser-driven plasma to generate high-energy, highly polarized proton beams with minimal polarization loss.

Findings

Proton beams reach energies near 0.5 GeV.

Polarization ratio of approximately 94%.

Effective suppression of polarization loss during acceleration.

Abstract

We propose a scheme to overcome the great challenge of polarization loss in spin-polarized ion acceleration. When a petawatt laser pulse penetrates through a compound plasma target consisting of a double layer slab and prepolarized hydrogen halide gas, a strong forward moving quasistatic longitudinal electric field is constructed by the self-generated laser-driven plasma. This field with a varying drift velocity efficiently boosts the prepolarized protons via a two-stage coherent acceleration process. Its merit is not only achieving a highly energetic beam but also eliminating the undesired polarization loss of the accelerated protons. We study the proton dynamics via Hamiltonian analyses, specifically deriving the threshold of triggering the two-stage coherent acceleration. To confirm the theoretical predictions, we perform three-dimensional PIC simulations, where unprecedented proton beams with energy approximating half GeV and polarization ratio $\sim$ 94\% are obtained.