Design and test of 704 MHz and 2.1 GHz normal conducting cavities for low energy RHIC electron cooler

Abstract

The low energy RHIC electron cooler (LEReC) is currently under commissioning at BNL to improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon. The linac of LEReC consists of a dc photoemission gun, one 704 MHz superconducting radio frequency booster cavity, and three normal conducting cavities. It is designed to deliver a 1.6–2.6 MeV electron beam, with peak-to-peak momentum spread dp/p of less than ±7×10^{-4}. Two of the three normal conducting cavities will be used in LEReC for energy spread correction: a single-cell 704 MHz cavity for energy dechirping and a three-cell 2.1 GHz third harmonic cavity for rf curvature correction. In this paper, we present the designs and rf test results of these two cavities.