Manipulation of $\gamma$ ray polarization in Compton scattering

TL;DR

This paper explores how to control the polarization of high-brilliance gamma rays produced via Compton scattering, revealing the underlying spin transfer mechanisms and proposing polarization as a tool to observe nonlinear effects.

Contribution

It uncovers the spin transfer mechanisms in nonlinear Compton scattering and demonstrates how polarization can be used to observe multi-photon absorption effects.

Findings

Polarization mainly contributed by electron spin in multi-photon absorption.

High-brilliance and high-polarization are challenging to achieve simultaneously.

Gamma-ray polarization signatures can reveal nonlinear Compton scattering effects.

Abstract

High-brilliance high-polarization $\gamma$ rays based on Compton scattering are of great significance in broad areas, such as nuclear, high-energy, astro-physics, etc. However, the transfer mechanism of spin angular momentum in the transition from linear, through weakly into strongly nonlinear processes is still unclear, which severely limits the simultaneous control of brilliance and polarization of high-energy $\gamma$ rays. In this work, we investigate the manipulation mechanism of high-quality polarized $\gamma$ rays in Compton scattering of the ultrarelativistic electron beam colliding with an intense laser pulse. We find that the contradiction lies in the simultaneous achievement of high-brilliance and high-polarization of $\gamma$ rays by increasing laser intensity, since the polarization is predominately contributed by the electron (laser photon) spin via multi-photon (single-photon) absorption channel. Moreover, we confirm that the signature of $\gamma$-ray polarization can be applied for observing the nonlinear effects (multi-photon absorption) of Compton scattering with moderate-intensity laser facilities.