Overview of SNS Cryomodule Performance

Thomas Jefferson National Accelerating Facility (Jefferson Lab) has completed production of 24 Superconducting Radio Frequency (SRF) cryomodules for the Spallation Neutron Source (SNS) superconducting linac. This includes one medium-β (0.61) prototype, eleven medium-β and twelve high-β (0.81) production cryomodules. Nine medium-β cryomodules as well as two high-β cryomodules have undergone complete operational performance testing in the Cryomodule Test Facility at Jefferson Lab. The set of tests includes measurements of maximum gradient, unloaded Q (Q
0
), microphonics, and response to Lorentz forces. The Q
ext
’s of the various couplers are measured and the behavior of the higher order mode couplers is examined. The mechanical and piezo tuners are also characterized. The results of these performance tests will be discussed in this paper.