Higher order mode damper for low energy RHIC electron cooler SRF booster cavity

TL;DR

This paper presents the design and testing of a higher order mode damper for a superconducting RF booster cavity in the LEReC linac, aimed at controlling HOMs to meet strict energy spread requirements for low energy RHIC electron cooling.

Contribution

It introduces a multiphysics design of a HOM damper for a 704 MHz SRF booster cavity and provides experimental validation of its effectiveness.

Findings

HOM damper effectively reduces HOMs in the cavity.

Experimental results show improved energy spread control.

Design meets the stringent requirements for LEReC operation.

Abstract

To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under commissioning at BNL. The Linac of LEReC is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with rms dp/p less than 5e-4. A 704 MHz superconducting radio frequency (SRF) booster cavity in this Linac provides up to 2.2 MeV accelerating voltage. With such a low energy and very demanding energy spread requirement, control of Higher Order Modes (HOMs) in the cavities becomes critical and needs to be carefully evaluated to ensure minimum impact on the beam. In this paper, we report the multiphysics design of the HOM damper for this cavity to meet the energy spread requirement, as well as experimental results of the cavity with and without the HOM damper.