THIXA —  SRF Technology V   (29-Jun-23   10:40—13:00)
Paper Title Page
THIXA01 Investigation of Plasma Processing for Coaxial Resonators 960
 
  • W. Hartung, W. Chang, K. Elliott, S.H. Kim, T. Konomi, K. Saito, P.R. Tutt, T. Xu
    FRIB, East Lansing, Michigan, USA
 
  Plasma processing has been investigated by several facilities as a method to mitigate degradation of SRF cavity performance. It provides an alternative to removal and disassembly of cryomodules for refurbishment of each cavity via repeat etching and rinsing. Promising results have been obtained by several groups. Studies of plasma processing for quarter-wave resonators (QWRs) and half-wave resonators (HWRs) were undertaken at FRIB, where a total of 324 such resonators are presently in operation. Plasma ignition and optimization measurements were done with room-temperature-matched input couplers. Plasma cleaning tests were done on several QWRs using the fundamental power coupler (FPC) to drive the plasma. We investigated the usefulness of higher-order modes (HOMs) to drive the plasma. HOMs allow for less mismatch at the FPC and hence lower field in the coupler relative to the cavity. Before-and-after cold tests showed a significant reduction in field emission X-rays with judicious application of plasma processing.  
slides icon Slides THIXA01 [2.060 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA01  
About • Received ※ 01 September 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023  
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THIXA02
Plasma Cleaning at FNAL: LCLS-II HE vCM Results and Ongoing Studies on Spoke Resonators  
 
  • P. Berrutti
    Fermilab, Batavia, Illinois, USA
 
  Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Plasma cleaning has been proven effective in eliminating multipacting and in preserving the field emission free performance of the LCLS-II HE vCM. Using high order modes (HOMs) for plasma ignition allows overcoming limitations imposed by weakly coupled fundamental modes. HOMs ignition can be applied to different SRF cavities making plasma processing potentially possible for any cavity geometry, including spoke resonators like the SSR1 for PIP-II. The results of plasma processing of LCLS-II HE cavities in vCM are presented, along with the summary of the plasma cleaning operations in the CM test cave. The preliminary results of plasma cleaning tests of SSR1 cavities and future plans are discussed.
 
slides icon Slides THIXA02 [7.045 MB]  
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THIXA03 Cryocooler Application for Accelerator and Development Status of Powerful Cryocooler at SHI Ltd. 968
 
  • T. Ikeda, S. Sasazaki
    SHI, Tokyo, Japan
 
  Advances in recent Nb₃Sn cavity development makes possible to operate the cavities with Qo ~ 1xE10 at 4.3 K and to design SRF accelerator in which the cavities are cooled directly with small mechanical cryocoolers instead of using liquid helium. Conduction-cooling with cryocoolers greatly simplify the overall design and also contribute for cost saving of an SRF accelerator, making the SRF technology feasible for industrial accelerators. However, in the case of using current cryocooler systems (like Gifford-McMahon cryocooler, Pulse-Tube cryocooler, etc.) for the conduction-cooling, since the cooling capacity per unit is small, multiple units will be used in combination depending on the required cooling capacity, it will cause problems in terms of power consumption (efficiency), footprint, and maintenance costs. Therefore, SHI have been developing a large-capacity and high-efficiency 4KGM-JT (Gifford-McMahon-Joule-Thomson) cryocooler system in the 10 W class at 4.2 K. This contribution will report the overview of this cryocooler system and its status of development.  
slides icon Slides THIXA03 [1.638 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA03  
About • Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023
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THIXA04
Development of a Prototype Superconducting Radio-Frequency Cavity for Conduction-Cooled Accelerators  
 
  • G. Ciovati, S. Balachandran, G. Cheng, E.F. Daly, P. Dhakal, K.A. Harding, F. Marhauser, T. Powers, U. Pudasaini, R.A. Rimmer, H. Vennekate
    JLab, Newport News, Virginia, USA
  • J.P. Anderson, B.R.L. Coriton, L.D. Holland, K.R. McLaughlin, D.A. Packard, D.M. Vollmer
    GA, San Diego, California, USA
  • A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • J. Rathke
    TechSource, Los Alamos, New Mexico, USA
  • T. Schultheiss
    TJS Technologies, Commack, New York, USA
 
  Funding: Work supported by the U.S. DOE, ARDAP Office, under contract No. DE-AC05-06OR23177. SB¿s microscopy work at the NHMFL was partly supported by the U.S. DOE, HEP Office under Award No. DE-SC0009960.
Recent progress in the development of high-quality Nb₃Sn film coatings along with the availability of cryocoolers with high cooling capacity at 4 K makes it feasible to operate SRF cavities cooled by thermal conduction at relevant accelerating gradients for use in accelerators. We have developed a prototype single-cell cavity to prove the feasibility of operation up to the accelerating gradient required for 1 MeV energy gain, cooled by conduction with cryocoolers. The cavity has a ~3 ¿m thick Nb₃Sn film on the inner surface, deposited on a ~4 mm thick bulk Nb substrate and a bulk ~7 mm thick Cu outer shell with three Cu attachment tabs. The cavity was tested up to a peak surface magnetic field of 53 mT in liquid He at 4.3 K. A horizontal test cryostat was designed and built to test the cavity cooled with three cryocoolers. The rf tests of the conduction-cooled cavity achieved a peak surface magnetic field of 50 mT and stable operation was possible with up to 18.5 W of rf heat load. The peak frequency shift due to microphonics was 23 Hz. These results represent the highest peak surface magnetic field achieved in a conduction-cooled SRF cavity to date
 
slides icon Slides THIXA04 [3.906 MB]  
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THIXA05 Conduction-Cooled SRF Cavities: Opportunities and Challenges 973
 
  • N.A. Stilin, H. Conklin, T. Gruber, A.T. Holic, M. Liepe, T.I. O’Connell, P. Quigley, J. Sears, V.D. Shemelin, J. Turco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Thanks to improvements in the performance of both commercial cryocoolers and Nb₃Sn-coated superconducting radio-frequency (SRF) cavities, it is now possible to design and build compact, SRF cryomodules without the need for liquid cryogenics. In addition, these systems offer robust, non-expert, turn-key operation, making SRF technology significantly more accessible for smaller-scale applications in fields such as industry, national security, medicine, environmental sustainability, etc. To fully realize these systems, many technical and operational challenges must be overcome. These include properly cooling the SRF cavity via thermal conduction and designing high-power (~ 100 kW continuous) RF couplers which dissipate minimal heat (~ 1 W) at 4.2 K. This presentation will discuss these challenges and the solutions which have been developed at Cornell University and elsewhere.  
slides icon Slides THIXA05 [7.219 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-THIXA05  
About • Received ※ 27 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 04 July 2023 — Issue date ※ 08 July 2023
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THIXA06
Dark Matter and Gravitational Waves Experiments with SRF Cavities  
 
  • B. Giaccone, A. Grassellino, S. Posen, A.S. Romanenko
    Fermilab, Batavia, Illinois, USA
 
  Funding: This material is based upon work supported by the U.S. DOE, SC, National QIS Research Centers, Superconducting Quantum Materials and Systems Center (SQMS) under contract n. DE-AC02-07CH11359
Recent efforts have shown that the SRF technology developed for accelerators can be successfully applied to new applications, including quantum computing, dark matter searches and beyond the standard model physics. The ultra-high quality factor of SRF cavities can allow to achieve unprecedented sensitivity in fields outside of the usual accelerator applications, for examples in dark photon and axion searches (both as dark matter candidates and lab-produced particles). Applications of SRF cavities for gravitational waves searches are also being investigated. The SQMS Physics and Sensing thrust is leveraging SRF cavities and QIS to search for new particles and BSM physics. This talk will highlight experiments where SRF cavities have already set experimental bounds on new physics.
 
slides icon Slides THIXA06 [5.984 MB]  
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THIXA07
Compact, High-Power Superconducting Electron Linear Accelerators for Environmental and Industrial Applications: Projects and Status  
 
  • J.C.T. Thangaraj, R. Dhuley, C.J. Edwards, I.V. Gonin, S. Kazakov, T.N. Khabiboulline, T.K. Kroc, T.H. Nicol, W. Pellico, A. Saini, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  We have developed and demonstrated a novel superconducting accelerator technology ¿ conduction cooling - that eliminates the need for liquid Helium, thus dramatically simplifying the infrastructure needed to access SRF technology for industrial applications. Our machine combines R&D breakthroughs in high-temperature SRF cavities (Nb₃Sn), cost-effective radio-frequency sources, modern technology cryo-coolers, and high-average current electron guns. We will describe currently active conduction-cooled accelerator projects at 650 MHz and 1.3 GHz. We will also present the experimental results on the conduction cooling of SRF cavities and briefly discuss results from other labs. Our compact linac is designed to generate electron beam energies up to 10 MeV in continuous-wave operation. Our detailed thermal, RF, and beam transport simulations show that a single accelerator module can deliver average beam power as high as 250 kW. We can reach up to 1 MW by combining several modules. Compact and light enough to mount on mobile platforms, our machine will enable applications such as treating contaminants in water, innovative pavement construction, and X-ray medical device sterilization.  
slides icon Slides THIXA07 [3.113 MB]  
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