Pressure Relieving Approach for the S³FEL Cryogenic Distribution System

Abstract Shenzhen Superconducting Soft-X-ray Free Electron Laser (S 3 FEL), located at Shenzhen, China, aims to construct a new light source that can generate high brightness X-Ray pulses between 40 eV and 1 keV at repetition rate up to 1 MHz. The S 3 FEL is based on superconducting accelerator technology comprised of 25 cryomodules (CMs) operating at 2 K temperature with 5 K thermal intercept circuit and 40 K thermal shield. The cryogenic distribution system (CDS) supplies and returns cryogens to 2 K, 5 K and 40 K flow circuits of the CMs strings, via vacuum insulated cryogenic pipes, valve boxes, and feed and end caps. To prevent overpressure of the process circuits of CDS and CMs, pressure relief devices shall be sized for all circuits to meet capacity requirements. In this paper, all credible failure scenarios and the determination of heat flux will be presented. The preliminary design results of the relief system will be discussed. Also, the relieving approach of sub-atmospheric 2 K circuit which has dual pressure ratings in the CM will be discussed.