Electron Bunch Train Excited Higher-Order Modes in a Superconducting RF Cavity

TL;DR

This paper explores how higher-order modes excited by electron bunch trains in superconducting RF cavities can be used for beam diagnostics, supported by theoretical modeling and experimental validation.

Contribution

It introduces a new approach utilizing beam harmonics in HOM spectra for improved beam diagnostics in SRF accelerators.

Findings

HOM spectra contain high signal-to-noise ratio beam harmonics.

Theoretical model aligns with experimental results.

Bunch train excited HOMs are effective for beam diagnostics.

Abstract

Higher-order mode (HOM) based intra-cavity beam diagnostics has been proved effectively and conveniently in superconducting radio-frequency (SRF) accelerators. Our recent research shows that the beam harmonics in the bunch train excited HOM spectrum, which have much higher signal-to-noise ratio than the intrinsic HOM peaks, may also be useful for beam diagnostics. In this paper, we will present our study on bunch train excited HOMs, including the theoretic model and recent experiments carried out based on the DC-SRF photoinjector and SRF linac at Peking University.