Transition radiation from electrons with orbital angular momentum

TL;DR

This paper explores how electrons with high orbital angular momentum produce distinctive transition radiation with high circular polarization, enabling measurement of their orbital momentum.

Contribution

It provides a theoretical analysis of transition radiation from electrons with orbital angular momentum, highlighting the polarization effects related to their magnetic moments.

Findings

Transition radiation exhibits up to 70% circular polarization.

The polarization degree correlates with the electron's orbital angular momentum.

Potential for using polarization measurements to determine electron OAM values.

Abstract

Several experimental groups have recently obtained the so called vortex electrons (electrons with orbital angular momentum (OAM) of l = 100h) with energies of 300 keV. The gyromagnetic ratio of such electrons becomes proportional to the OAM value, which leads to the corresponding increase of the electron magnetic moment. In this paper we investigate the transition radiation from the "charge + magnetic moment" system using the theory of classical electrodynamics. The circular polarization of optical transition radiation amounts up to 70%, which allows to use this effect for the independent measurement of the electron orbital momentum value.