Generation and measurement of gamma rays with axially symmetric polarization states via Compton scattering

Abstract

Highly polarized gamma rays with linear or circular polarization are essential light sources for nuclear and particle physics experiments, astronomical detector evaluations, and relativistic electron beam diagnostics. In this study, we demonstrate gamma-ray generation via Compton scattering with unique polarization states, termed axially symmetric polarization. To investigate this, we developed a polarimeter for Compton gamma-ray sources to measure their two-dimensional polarization distribution. We found two methods to generate gamma rays whose polarization axis follows the azimuthal direction. The first method exploits the inherent azimuthal polarization of gamma rays produced using a circularly polarized laser. In this configuration, the gamma rays along the central axis are circularly polarized, while the linear polarization components in the outer region of the beam cross section are aligned azimuthally. The second method utilizes azimuthal polarization that arises in the outer region of the beam due to the incoherent superposition of multiple linearly polarized gamma rays with varying polarization axes, generated by an axially symmetric polarized laser. Additionally, our calculations indicate the feasibility of generating gamma rays with polarization axes oriented along the radial direction. This radial polarization, observed near the beam axis, results from the incoherent superposition of second harmonic gamma rays produced through nonlinear interactions induced by an intense axially symmetric polarized laser.