Operation of the 56 MHz Superconducting RF Cavity in RHIC with Higher Order Mode Damper

TL;DR

This paper reports on the operation and performance of a novel 56 MHz superconducting RF cavity in RHIC, highlighting its design, integration, and impact on luminosity and bunch length during heavy ion collisions.

Contribution

It introduces the first superconducting quarter wave resonator operating in a high-energy storage ring and details its innovative higher order mode damping system.

Findings

Luminosity improved with the cavity at 300 kV

Bunch length was reduced during operation

Successful integration of the cavity in RHIC with different collision types

Abstract

A 56 MHz superconducting RF cavity was designed and installed in the Relativistic Heavy Ion Collider (RHIC). It is the first superconducting quarter wave resonator (QWR) operating in a high-energy storage ring. We discuss herein the cavity operation with Au+Au collisions, and with asymmetrical Au+He3 collisions. The cavity is a storage cavity, meaning that it becomes active only at the energy of experiment, after the acceleration cycle is completed. With the cavity at 300 kV, an improvement in luminosity was detected from direct measurements, and the bunch length has been reduced. The uniqueness of the QWR demands an innovative design of the higher order mode dampers with high-pass filters, and a distinctive fundamental mode damper that enables the cavity to be bypassed during the acceleration stage.