  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.
