DESY 2011 CMTB Experiment Summary PXFEL2-1 cryomodule used to investigate LP and CW operation in the summer of 2011: CW operation up to 7.5 MV/m Determined heating on HOM couplers due to low heat conduction feedthroughs, did not cause quench 4.8 watts additional heat load due to end group heating Measurements at 1.8K operation showed lower heating on endgroups but still significant Operation at 7.5 MV/m CW not verified in this experiment but did operate at 3.3 MV/m, and at 8.8 MV/m but not all cavities 1.IPAC2012, J. Sekutowicz, CW Operation Test of XFEL-Like Cryomodule

DESY 2013 Components Developed for CW Operation Summary of R&D: Focus on building prototypes for CW and LP operation – For CW higher then 7MV/m LP operation is intended – Modules are currently limited to heat loads of (static + dynamic) 20 W due to the diameter of the 2 phase tube and 12 cryomodule string constraints – 17 cryomodules would need to be replaced with modified ones for CW operating between 11 and 16 MV/m – Heat loads Current Configuration Capacity – 2450 W, Heat Load 1175 W CW/LP operation Capacity W, Heat Load 3320 W Modified HOM couplers – Reduce the residual magnetic flux of fundamental mode – Hook modified with additional inductance which moves the antenna out of the coupler and into a cutoff tube – Ready for testing prototype end of this year – Feed throughs now made from highly conductive materials : Nb, moly, sapphire, Nb probe tip brazed – Copper braid strapping to 2-phase return tube IPAC 2013, J. Sekutowicz, Components for CW operation of the XFEL Linac

Additional concerns for CW operation Beam line HOM absorbers – Between cryomodules – Currently 3.8 Watts 10% DF – CW ~ 100 Watts

Cryostat vessels -13 from Zanon and 8 from IHEP/Beijing

OD- 1.06m OAH – 1.56m

XFEL Final TDR