Plasma acceleration of polarized particle beams

TL;DR

This review surveys the developments in generating and diagnosing spin-polarized beams via laser–plasma interactions, with emphasis on spin dynamics, target preparation, and polarization-preserving injection. It consolidates spin-precession physics under the T-BMT framework, radiative polarization effects, and practical scaling laws that guide depolarization. The article compiles experimental demonstrations and theoretical proposals for polarized electrons, positrons, ions, and polarized gamma quanta, highlighting in-situ polarization schemes and near-term pathways toward high-current polarized injectors for future high-energy colliders and nuclear/particle physics applications. The work underscores the potential of laser-plasma sources to deliver ultrashort, high-current polarized beams that could revolutionize DIS, fusion diagnostics, and accelerator science, while outlining critical experimental milestones and the need for advanced polarimetry and high-intensity laser capabilities.

Abstract

Spin-polarized particle beams are of interest for applications like deep-inelastic scattering, e.g. to gain further understanding of the proton's nuclear structure. With the advent of high-intensity laser facilities, laser-plasma-based accelerators offer a promising alternative to standard radiofrequency-based accelerators, as they can shorten the required acceleration length significantly. However, in the scope of spin-polarized particles, they bring unique challenges. This paper reviews the developments in the field of spin-polarized particles, focusing on the interaction of laser pulses and high-energy particle beams with plasma. The relevant scaling laws for spin-dependent effects in laser-plasma interaction, as well as acceleration schemes for polarized leptons, ions, and gamma quanta, are discussed.

Figures (14)

• Figure 1: Schematic overview of the relevant effects affecting particle spin in laser-plasma interaction. Reproduced under the terms of the CC-BY license from Thomas2020_scaling. Copyright 2020, The Authors, published by American Physical Society.
• Figure 2: Magnetic holding setup for the acceleration of polarized Helium-3. Reproduced under the terms of the CC-BY license from Fedorets2022_he3. Copyright 2022, The Authors, published by MDPI AG.
• Figure 3: (a) Potential experimental configuration for laser-driven wakefield acceleration of spin-polarized electrons. (b) Schematic of polarized electron production from an HCl target using multiple lasers for alignment, photo dissociation and ionization. Reproduced under the terms of the CC-BY license from Wu2019_lwfa. Copyright 2019, The Authors, published by IOP Publishing Ltd.
• Figure 4: Dependence of beam charge and polarization degree, as well as emittance and peak current, on parameters of the colliding laser pulse. The driving laser pulse is fixed to $a_0 = 2.5$ and $w_0 = 20$$\mu$m. Reproduced under the terms of the CC-BY license from Bohlen2023_colliding_pulse. Copyright 2023, The Authors, published by American Physical Society.
• Figure 5: The single-species photocathode scheme for polarized electrons. (a), (b) show the plasma and beam density around the laser focus and after driver pinching, respectively. (c), (d) show the Yb ion density at the corresponding time steps. Reproduced under the terms of the CC-BY license from Nie2022_single_species. Copyright 2022, The Authors, published by American Physical Society.