Synchrotron radiation from a charge moving along a helical orbit inside a dielectric cylinder

TL;DR

This paper analyzes the electromagnetic radiation emitted by a charged particle moving helically inside a dielectric cylinder, revealing conditions for enhanced radiation peaks and increased intensity compared to a homogeneous medium.

Contribution

It derives new expressions for the electromagnetic fields and spectral-angular distribution of radiation, highlighting the impact of the dielectric cylinder on radiation enhancement and peak formation.

Findings

Strong narrow peaks in angular distribution under Cherenkov condition

Radiated energy can exceed that in a homogeneous medium by orders of magnitude

Presence of the cylinder significantly increases radiation intensity

Abstract

The radiation emitted by a charged particle moving along a helical orbit inside a dielectric cylinder immersed into a homogeneous medium is investigated. Expressions are derived for the electromagnetic potentials, electric and magnetic fields, and for the spectral-angular distribution of radiation in the exterior medium. It is shown that under the Cherenkov condition for dielectric permittivity of the cylinder and the velocity of the particle image on the cylinder surface, strong narrow peaks are present in the angular distribution for the number of radiated quanta. At these peaks the radiated energy exceeds the corresponding quantity for a homogeneous medium by some orders of magnitude. The results of numerical calculations for the angular distribution of radiated quanta are presented and they are compared with the corresponding quantities for radiation in a homogeneous medium. The special case of relativistic charged particle motion along the direction of the cylinder axis with non-relativistic transverse velocity (helical undulator) is considered in detail. Various regimes for the undulator parameter are discussed. It is shown that the presence of the cylinder can increase essentially the radiation intensity.