Stochasticity in radiative polarization of ultrarelativistic electrons in an ultrastrong laser pulse

Abstract

Stochastic effects in the spin (de)polarization of an ultrarelativistic electron beam during photon emissions in a counterpropagating ultrastrong focused laser pulse in the quantum radiation reaction regime are investigated. We employ a Monte Carlo method to describe the electron dynamics semiclassically and photon emission and electron radiative polarization quantum mechanically. While in the latter the photon emission is inherently stochastic, we are able to identify its imprints in comparison with the semiclassical stochasticity-free method of radiative polarization applicable in the quantum regime. With an initially-spin-polarized electron beam, the impact of stochastic effects of photon emissions on the spin observable is demonstrated in the dependence of the depolarization degree on the electron scattering angle and the final electron energy (spin stochastic diffusion). With an initially unpolarized electron beam, the stochastic effects on the spin are exhibited in enhancing the known effect of splitting of the electron beam along the propagation direction into two oppositely polarized parts by an elliptically polarized laser pulse. The considered stochastic effects for the spin are observable with currently achievable laser and electron-beam parameters.

Radiative polarization dynamics of relativistic electrons in an intense electromagnetic field

“…where This continuous expression completely agrees with the corresponding formula in Refs. [48,49], which is also evidence for the correctness of our MCPV model.…”

“…The polarization vector completely describes the spin state of the electron and corresponds to the spin vector in the classical theory. So if we utilize the polarization vector to describe the evolution of the relativistic electron spin, the complete information on spin will be kept throughout the simulation, and some models have been developed based on this idea [47][48][49].…”

“…Our Monte Carlo polarization vector (MCPV) model maintains the complete information on the spin polarization of the electron at any simulation moment, and it has a computational efficiency higher than that of the 3D-SQA model and a time step condition more relaxed than that of the 3D-SQA model. Compared with other continuous models described by the mean spin vector [48,49], the MCPV model has the advantage of handling photon emission and electron spin simultaneously, and is more suitable for the interaction in the quantum regime. The correctness of the MCPV model is confirmed by the successful reproduction of the Sokolov-Ternov effect and the comparison of simulation results with other models in the literature.…”

Production of multi-oriented polarization for relativistic electron beams via a mutable filter for nonlinear Compton scattering

“…The simulation method is valid under the assumptions that γ 1, a 0 1, and the electromagnetic fields are small with respect to the Schwinger limit field E crit = m 2 e c 3 /e ≈ 1.32 × 10 18 V/m [41]. Our code is verified by reproducing the result of Sokolov-Ternov effect and other spin polarization models [20,64,65].…”

Generation of quasi-monoenergetic proton beams via quantum radiative compression

“…2]. To describe the plasma dynamics accurately in the applied QRR regime, we have implemented the spin-resolved Monte Carlo processes of electron dynamics and radiation [47][48][49][50][51] into the 3D particle-in-cell (PIC) code EPOCH [52]. With up-coming laser facilities [16][17][18][19][20][21], proton bunches with a peak energy of GeV order, relative energy spread of few percents and total number N p ∼ 10 10 can be obtained [see Fig.…”