Peterson, T.J. Arkan, T.T. Ginsburg, C.M. He, Y. Kaluzny, J.A. McGee, M.W. Orlov, Y.O. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-THPB119 English 1417-1421 THPB119 cryomodule vacuum cryogenics cavity operation Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-THPB119 http://srf2015.vrws.de/papers/thpb119.pdf We will present the design of the 1.3 GHz cryomodule for the Linear Coherent Light Source upgrade (LCLS-II) at SLAC. Fermilab is responsible for the design of this cryomodule, a modified TESLA-style cryomodule to accommodate continuous wave (CW) mode operation and LCLS-II beam parameters, consisting of eight 1.3 GHz superconducting RF cavities, a corrector magnet package, and instrumentation. Thirty-five of these cryomodules, approximately half built at Fermilab and half at Jefferson Lab, will become the main accelerating elements of the 4 GeV linac. The modifications and special features of the cryomodule include: thermal and cryogenic design to handle high heat loads in CW operation, magnetic shielding and cool-down configurations to enable high quality factor (Q0) performance of the cavities, liquid helium management to address the different liquid levels in the 2-phase pipe with 0.5% SLAC tunnel longitudinal slope, support structure design to meet California seismic design requirements, and with the overall design consistent with space constrains in the existing SLAC tunnel. The prototype cryomodule assembly will begin in August 2015 and is to be completed in early 2016.