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Description
This paper describes the initial operational experience gained from testing Linac Coherent Light Source II (LCLS-II) cryomodules at Fermilab’s Cryomodule Test Facility (CMTF). Strategies for a controlled slow cooldown to 100K and a fast cooldown past the niobium superconducting transition temperature of 9.2K will be described. The test stand for the cryomodules at CMTF is sloped to match gradient in the LCLSII tunnel at Stanford Linear Accelerator (SLAC) laboratory, which adds an additional challenge to stable liquid level control. Control valve regulation, Radio-Frequency (RF) power compensation, and other methods of stabilizing liquid level and pressure in cryomodule 2.0 K SRF cavity circuit will be discussed. Several different pumping configurations using cold compressors and warm vacuum pumps have used on the cryomodule 2.0 K return line and the associated results will be described.