Shadowing of the electromagnetic field of a relativistic electron

TL;DR

This paper investigates how the electromagnetic self-field of a relativistic electron is partially shadowed by a material object, affecting the intensity of coherent diffraction radiation and potentially reducing total radiated energy.

Contribution

It provides experimental evidence of the shadowing effect on the electron's self-field in coherent radiation sources, highlighting its impact on radiation intensity and energy output.

Findings

Shadowing reduces diffraction radiation when the screen is close and on the same side as the source.

No shadowing effect observed when the screen is on the opposite side.

Shadowing can significantly decrease total radiated energy in long radiators.

Abstract

In coherent radiation sources (diffraction radiation, Smith-Purcell effect, etc.) based on relativistic electrons passing by a material radiator, the electron self-field is partly shadowed after each part of the radiator over a distance of the order of the formation length g2l. This effect has been investigated on coherent diffraction radiation (DR) by electron bunches. An absorbing half-plane screen was placed at various distances L before a standard DR source (inclined half-plane mirror). The DR intensity was reduced when the screen was at small L and on the same side as the mirror. No reduction was observed when the screen was on the opposite side. The shadowing effect can significantly reduce the total energy radiated in a long radiator.