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MOP032 Effect of Low Temperature Infusion Heat Treatments and "2/0" Doping on Superconducting Cavity Performance cavity, ECR, niobium, SRF 118
  • P.N. Koufalis, M. Ge, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  Under specific circumstances, low temperature infusion heat treatments of niobium cavities have resulted in the ubiquitous "Q-rise". This is an increase in quality factor with increasing field strength or equivalently a decrease in the temperature-dependent component of the surface resistance. We investigate the results of various infusion conditions with infusion bake time as a free parameter. To study the very near surface effects of infusion, we employ HF rinsing, light VEP, and oxypolishing to remove several or tens of nm at a time. We present results from RF performance tests of low temperature infusion heat treated niobium cavities, and correlate these with SIMS impurity depth profiles obtained from witness samples. We also present results of a cavity doped at 800 C with the "2/0" recipe.  
DOI • reference for this paper ※  
About • paper received ※ 26 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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TUP034 Microphonics Testing of LCLS II Cryomodules at Jefferson Lab cavity, cryomodule, cryogenics, vacuum 493
  • T. Powers, N.C. Brock, G.K. Davis
    JLab, Newport News, Virginia, USA
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Jefferson Lab is partnering with Fermilab to build the 36 cryomodules for the LCLS II accelerator that will be installed at SLAC. The cavities have design loaded-Q of 4×107, which means that it has a control bandwidth of 16 Hz. The JLab prototype cryomodule was instrumented with a series of seven accelerometers, and impulse hammer response measurements were made while the cryomodule was being built and after it was installed in the JLab cryomodule test facility. This was done so that we could understand the shapes of the modes of the structure. These results were compared to impulse hammer testing from the outside of the cryomodule and to individual cavity frequency shifts when the cryomodule was cold. The prototype cryomodule had excessive microphonics of 150 Hz peak due to a thermos-acoustic oscillation. Design modifications were implemented and subsequently the cryomodules had microphonics on the order of 10 to 20 Hz. Results of the modal analysis as well as the background microphonics observed when operated under various cryogenic conditions and with different modifications will be presented.
DOI • reference for this paper ※  
About • paper received ※ 21 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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