CLASSE NEWS | 5 Aug 2014
Cornell has successfully completed RF testing of the first LCLSII 9-cell cavity in a realistic cryomodule configuration. This first cryomodule test of an LCLSII cavity is a very important milestone for the LCLSII project. The Cornell team demonstrated for the first time that the important LCLSII cavity intrinsic quality factor (Q0) specification can be achieved in a cryomodule configuration, and has set a new record for the efficient operation of an SRF cavity in a cryomodule.
The cavity (TB9ACC012) was etched, N-doped and tank welded by the Fermilab team, and then was sent to Cornell for final cleaning (HPR), mounting, and installation into the Cornell Horizontal-Test-Cryomodule (HTC). After fast cool-down from 100K to operating temperature with large temperature gradients over the cavity during cool-down, the intrinsic quality factor Q0 at 2K, 14 MV/m was (3.2+-0.3)E10, thus significantly exceeding LCLSII specifications of 2.7E10.
Detailed cool-down studies with the cavity in the HTC showed that large spatial temperature gradients over the cavity during cool-down (rather than large temporal gradients) are critical to reduce trapping of ambient magnetic field in the cavity walls.
LCLSII 9-cell Cavity exceeds Intrinsic Quality Factor Specification in Cryomodule for the First Time
