Practicability of methods to remove unpolarized electrons in SPH-based polarized electron sources

Ascertain which of the two proposed methods for removing unpolarized electrons when producing polarized electron beams from spin‑polarized hydrogen targets for laser wakefield acceleration is more practicable: (i) removal via ionization of the halide atoms or (ii) spatial separation of spin‑polarized hydrogen atoms from unwanted photoproducts that leaves only highly polarized hydrogen.

Background

Spin-polarized hydrogen (SPH) targets prepared by photodissociation of hydrogen halides can supply polarized electrons for laser-wakefield acceleration, but unavoidably contain unpolarized electrons from halide atoms. The literature proposes two approaches to eliminate these unpolarized electrons—either by targeted ionization or by spatial separation of the desired polarized hydrogen atoms from the residual photoproducts. The review highlights that it is currently unresolved which approach is more practical in experimental laser-plasma accelerator environments.