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Abstract

Spin-polarization of an ultrarelativistic electron beam head-on colliding
with an ultraintense laser pulse is investigated in the quantum
radiation-reaction regime. We develop a Monte-Carlo method to model electron
radiative spin effects in arbitrary electromagnetic fields by employing
spin-resolved radiation probabilities in the local constant field
approximation. Due to spin-dependent radiation reaction, the applied
elliptically polarized laser pulse polarizes the initially unpolarized electron
beam and splits it along the propagation direction into two oppositely
transversely polarized parts with a splitting angle of about tens of
milliradians. Thus, a dense electron beam with above 70\% polarization can be
generated in tens of femtoseconds. The proposed method demonstrates a way for
relativistic electron beam polarization with currently achievable laser
facilities.