Possible scheme for observing acceleration (Unruh) radiation

TL;DR

This paper proposes a method to observe Unruh radiation in free-electron lasers by detecting scattered virtual photons, highlighting potential experimental setups like the Stanford LCLS and high-energy collisions.

Contribution

It introduces a scheme to detect Unruh radiation via scattering in FELs, considering coherence effects and specific experimental configurations.

Findings

Unruh radiation can be enhanced by microbunching in FELs.

Coherent scattering of virtual photons is feasible in FEL environments.

Potential detection in high-energy electron beam collisions.

Abstract

In an FEL the electrons traveling through the undulator are surrounded in their own reference frame by Unruh radiation at a temperature of order 8,000 Kelvin. When these virtual photons scatter from the beam electrons they become real and can be detected. Because of the microbunching of the FEL electron beam this process proceeds coherently for a fraction of the electrons in the microbunch. This enhances the Unruh radiation which is still dominated by the copious spontaneous radiation in the same energy range. We discuss the particular case of the Stanford LCLS, as well as the case of extreme acceleration, when the x-ray beam is brought into collision with the 14 GeV electron beam.