Thermodynamic Analyses of the LCLS-II Cryogenic Distribution System

Abstract

Abstract-The Linac Coherent Light Source (LCLS) atStanford Linear Accelerator Center (SLAC) is in the process of being upgraded to a superconducting radio frequency (SRF) accelerator and renamed LCLS-II. This upgrade requires thirtyfive 1.3 GHz SRF cryomodules (CM) and two 3.9 GHz CM. A cryogenic distribution system (CDS) is in development by Fermi National Accelerator Laboratory to interconnect the CM Linac with the cryogenic plant (CP). The CDS design utilizes cryogenic helium to support the CM operations with a high temperature thermal shield around 55 K, a low temperature thermal intercepts around 5 K, and a SRF cavity liquid helium supply and subatmospheric vapor return both around 2 K. Additionally the design must accommodate a Linac consisting of two parallel cryogenic strings, supported by two independent CP utilizing CDS components such as distribution boxes, transfer lines, feed caps and endcaps. The paper describes the overall layout of the cryogenic distribution system and the major thermodynamic factors which influence the CDS design including heat loads, pressure drops, temperature profiles, and pressure relieving requirements. In addition the paper describes how the models are created to perform the analyses. 

Pressure safety approach for PIP-II cryogenic distribution system and cryomodules

“…To convert to heating rate, need time constant to apply for the duration of the heating period. Use same time constant as previously used for LCLSII transfer line which has similar geometry [9], 70 sec. This is based on experimental results from DESY/XFEL Cryomodule crash tests [7] for air ingress choked flow, with active cryo-pumping, using opening to vacuum from DN80 pumping port.…”

Physics Opportunities for the Fermilab Booster Replacement

“…E137 [103]) have been conducted in the past, but under conditions that optimized for long lived axion-like particles over a ∼ few 100 meter baseline with 10 20 electrons on target; there is considerable room for improvement for dark matter detection, specifically. Potentially useful electron beams also currently exist in the United States at Jefferson Lab CEBAF at 12 GeV [104] and the SLAC LCLS-II at 4-8 GeV (depending on upgrade) [105,106]. At CERN the secondary 100 GeV electron beam at the SPS is currently being utilized for dark photon searches by the NA64 experiment [107] and there are lower energy options currently available: the Mainz Mircotron MAMI-C [108] and the DAΦNE test beam facility at INFN Frascati [109] currently operate relativistic electron beams at few 100 MeV-GeV scale energies.…”