Gravitational Synchrotron Radiation from Storage Rings

TL;DR

This paper investigates gravitational waves generated by charged particles in storage rings, focusing on gravitational synchrotron radiation and its conversion from electromagnetic radiation, and assesses their detectability with current and future methods.

Contribution

It introduces the concept of gravitational synchrotron radiation in storage rings and analyzes its spectral properties and potential for detection.

Findings

GSR spectrum peaks at the storage ring fundamental frequency

GSR-induced spacetime perturbation is too weak for current detectors

Resonant conversion of EMSR to GWs could be detectable via 'light shining through a wall'

Abstract

We reinvestigate the gravitational waves (GWs) induced by charged particles in storage rings. There are two major components in such GWs. One is the gravitational synchrotron radiation (GSR), i.e., the direct emission by the bending of the trajectory of a relativistic charged particle, much like the conventional electromagnetic synchrotron radiation (EMSR), albeit with characteristic difference in their radiation spectra. While the conventional EMSR spectrum peaks at the critical frequency, $\omega_c=\gamma^3\omega_0\gg\omega_0$, the spectrum of GSR peaks at the storage ring fundamental frequency $\omega_0$, which is much lower. The other is the resonant conversion of EMSR to GWs at the same frequency through the storage ring bending magnets, i.e., the Gertsenshtein effect. Invoking LHC at CERN as a numerical example, we found that the spacetime perturbation associated with GSR, $h\sim 5\times 10^{-40}$, falls far below the sensitivity of GW detectors based on the LIGO-type Michelson interferometry approach. On the other hand, the GWs induced by the resonant conversion of EMSR have much higher frequencies and thus much localized, so it is conceivable to detect them through the reverse conversion, the so-called `light shining through a wall', process.