HOM-Damping Studies in a Multi-Cell Elliptical Superconducting RF Cavity for the Multi-Turn Energy Recovery Linac PERLE

TL;DR

This study analyzes and optimizes HOM damping techniques in a 5-cell superconducting RF cavity for the PERLE ERL, focusing on design, broadband performance, and thermal behavior to improve stability and efficiency.

Contribution

It introduces optimized HOM coupler designs for a multi-cell SRF cavity, enhancing damping of HOMs and ensuring efficient power extraction for the PERLE ERL.

Findings

Optimized coaxial HOM couplers improve damping of monopole and dipole modes.

Broadband HOM damping confirmed by time-domain and frequency-domain simulations.

Thermal analysis supports reliable operation of HOM couplers.

Abstract

Higher order mode (HOM) damping is a crucial issue for the next generation of high-current energy recovery linacs (ERLs). Beam-induced HOMs can store sufficient energy in the superconducting RF (SRF) cavities, giving rise to beam instabilities and increasing the heat load at cryogenic temperatures. To limit these effects, using HOM couplers on the cutoff tubes of SRF cavities becomes crucial to absorb beam-induced wakefields consisting of all cavity eigenmodes. The study presented here focuses on a 5-cell 801.58 MHz elliptical SRF cavity designed for the multi-turn energy recovery linac PERLE (Powerful Energy Recovery Linac for Experiments). Several coaxial coupler designs are analyzed and optimized to enhance the damping of monopole and dipole HOMs of the 5-cell cavity. The broadband performance of HOM damping is also confirmed by the time-domain wakefield and the frequency-domain simulations. In addition, the thermal behavior of the HOM couplers is investigated. A comparison between various HOM-damping schemes is carried out to guarantee an efficient HOM power extraction from the cavity.