A plasma photocathode for spin-polarized electron beams using excited hydrogen halides

2026/08/05 by Lars Reichwein, Thomas C. Wilson, Dimitris Sofikitis +6
Physics and Astronomy · #physics.plasm-ph

paper · pdf

7 pages, 4 figures

arxiv created 2026/08/05 · arxiv updated 2026/08/06

Abstract

Spin-polarized electron beams are essential tools for probing fundamental symmetries and for the search beyond the Standard Model. While plasma-based accelerators are a promising pathway towards higher-energy frontiers, they have so far failed to deliver a competitive polarized source: existing proposals are challenging to realize and achievable polarizations remain far below conventional sources. Here, we introduce a photocathode-like scheme, applied to a gas of pre-polarized hydrogen halides. A VUV and a visible laser pulse excite the halide atoms to create a two-component ionization medium, consisting of low-threshold excited halide and high-threshold polarized hydrogen. Particle-in-cell simulations show witness beams of approx. 10 pC retaining 97% of the initial polarization P₀, reaching P ≈ 68% for unaligned bonds (P₀ = 70%) and P=97% for aligned bonds (P₀ = 100%), rivaling state-of-the-art conventional sources.

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