Colliding pulse injection of polarized electron bunches in a laser-plasma accelerator

Abstract

Highly polarized, multi-kiloampere-current electron bunches from compact laser-plasma accelerators are desired for numerous applications. Current proposals to produce these beams suffer from intrinsic limitations to the reproducibility, charge, beam shape, and final polarization degree. In this paper, we propose colliding pulse injection (CPI) as a technique for the generation of highly polarized electron bunches from prepolarized plasma sources. Using particle-in-cell simulations, we show that colliding pulse injection enables trapping and precise control over electron spin evolution, resulting in the generation of high-current (multi-kA) electron bunches with high degrees of polarization (up to 95% for >2kA). Bayesian optimization is employed to optimize the multidimensional parameter space associated with CPI to obtain a percent-level energy spread, submicron normalized emittance electron bunches with 90% polarization using 100-TW class laser systems.