Measurement of the Per Cavity Energy Recovery Efficiency in the Single Turn CBETA Configuration

TL;DR

This paper reports precise measurements of energy recovery efficiency in the CBETA test accelerator, demonstrating near-perfect energy recovery per cavity in a single-turn superconducting ERL setup, crucial for future multi-turn designs.

Contribution

It provides the first direct measurement of per cavity energy recovery efficiency in a single-turn superconducting ERL, achieving over 99.2% efficiency per cavity.

Findings

Total one-turn power balance efficiency of 99.4%

Per cavity efficiency ranging from 99.2% to 99.8%

Single particle energy recovery efficiencies from 99.8% to 100.5%

Abstract

Prior to establishing operation of the world's first mulit-turn superconducting Energy Recovery Linac, (ERL) the Cornell-BNL Energy Recovery Test Accelerator (CBETA) was configured for one turn energy recovery. In this setup, direct measurement of the beam loading in each of the main linac cavities demonstrated high energy recovery efficiency. Specifically, a total one-turn power balance efficiency of 99.4%, with per cavity power balances ranging from 99.2-99.8%, was measured. When accounting for small particle losses occurring in the path length adjustment sections of the return loop, this corresponds to per cavity single particle energy recovery efficiencies ranging from 99.8 to 100.5%. A maximum current of 70 microamps was energy recovered, limited by radiation shielding of the beam stop in its preliminary installation.