Author: Jing, C.-J.
Paper Title Page
MOPTEV009 A Method for In-Situ Q0 Measurements of High-Quality SRF Resonators 221
 
  • S.V. Kuzikov, P.V. Avrakhov, C.-J. Jing, R.A. Kostin, Y. Zhao
    Euclid TechLabs, Solon, Ohio, USA
  • C.-J. Jing, C.-J. Jing
    ANL, Lemont, Illinois, USA
  • C.-J. Jing, R.A. Kostin
    Euclid Beamlabs, Bolingbrook, USA
  • R.A. Kostin, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • T. Powers, R.A. Rimmer
    JLab, Newport News, Virginia, USA
 
  Funding: The work was supported in the part by DoE SBIR grant #DE-SC0019687.
Accelerator projects such as LCLS-II naturally require low-loss superconducting (SRF) cavities. Due to strong demand for improving intrinsic quality factor (Q0), importance of accurate cavity characterization increases. We propose a method to measure Q0 in situ for an SRF resonator installed in its cryogenic module and connected with a RF feed source via a fixed RF coupler. The method exploits measurements of a response for an SRF resonator fed by an amplitude-modulated signal. Such a signal can be synthesized as a beat-wave composed of two frequencies that are close to the resonant frequency. Analyzing the envelope of the reflected signal, one can find the difference in reflection for the chosen frequencies and use them to compute the intrinsic Q. We also develop the methodology to carry out measurements of Q0 at the nominal cavity operating voltage. We verified our method in experiments with a room temperature copper resonator and with two SRF resonators including Fermilab’s 650 MHz cavity and JLab’s 1500 MHz cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPTEV009  
About • Received ※ 15 June 2021 — Revised ※ 26 August 2021 — Accepted ※ 19 February 2022 — Issue date ※ 06 April 2022
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SUPTEV010 Electrical and Thermal Properties of Cold-Sprayed Bulk Copper and Copper-Tungsten Samples at Cryogenic Temperatures 142
 
  • H. Pokhrel
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, P. Dhakal, J.K. Spradlin
    JLab, Newport News, Virginia, USA
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, Solon, Ohio, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, SBIR grant DE-SC00195589
The development of high thermal conductivity coatings with pure copper or copper-tungsten alloy could be beneficial to improve the heat transfer of bulk Nb cavities for conduction cooling applications and to increase the stiffness of bulk Nb cavities cooled by liquid helium. Cold-spray is an additive manufacturing technique suitable to grow thick coatings of either Cu or CuW on a Nb substrate. Bulk (~5 mm thick) coatings of Cu and CuW were deposited on standard 3 mm thick, high-purity Nb samples and smaller samples with 2 mm x 2 mm cross section were cut for measuring the thermal conductivity and the residual resistivity ratio. The samples were subjected to annealing at different temperatures and a maximum RRR of ~130 and ~40 were measured for the Cu samples and CuW samples, respectively.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPTEV010  
About • Received ※ 21 June 2021 — Revised ※ 13 August 2021 — Accepted ※ 15 November 2021 — Issue date ※ 21 March 2022
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THOTEV05
Ferro-Electric Fast Reactive Tuners for SRF  
 
  • N.C. Shipman, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, D. Valuch, W. Venturini Delsolaro
    CERN, Geneva, Switzerland
  • I. Ben-Zvi
    BNL, Upton, New York, USA
  • C.-J. Jing, A. Kanareykin
    Euclid TechLabs, Solon, Ohio, USA
 
  A Ferro-Electric Fast Reactive Tuner (FE-FRT) is a new type of tuner, utilising a novel ferro-electric material, which can change the frequency of an RF cavity on the sub-microsecond timescale and has the potential to reduce a cavity’s RF power requirements by an order of magnitude in some cases. During operation, power is continuously coupled out of the cavity, through the tuner, and reflected back into the cavity. By applying a high voltage across a ferro-electric within the tuner, the reactive load seen by the cavity is altered which causes a frequency shift in the cavity. The extremely fast response times of FE-FRTs make them especially suited to the correction of frequency variations caused by microphonics. New closed loop tuning measurements at CERN with a prototype FE-FRT and superconducting RF cavity have recently demonstrated excellent suppression of the cavity’s microphonics. The experimental set-up and the recent test results will be presented and the capabilities of this approach contrasted with more common systems, such as piezoelectric based tuners.  
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