THOTEV —  Thursday Oral SRF Technologies   (01-Jul-21   08:00—10:50)
Paper Title Page
Overview on Worldwide Development of SRF-Gun Cavities  
  • T. Konomi
    KEK, Ibaraki, Japan
  This talk is an overview of worldwide development of SRF-gun cavities including the recent activities at KEK, BNL, FNAL, HZB, HZDR and other laboratories. SRF electron guns have a possibility to realize high acceleration voltage and high beam repetition simultaneously in many accelerator applications. The design, fabrication, surface treatments and VT results of the SRF-gun cavities in each laboratory should be summarized. The cryomodule design with a low particulate cathode insertion system and the latest results in full cryostats should be presented.  
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THOTEV02 Stable Beam Operation in Compact ERL for Medical and Industrial Application at KEK 714
  • H. Sakai, M. Adachi, D.A. Arakawa, S. Eguchi, M.K. Fukuda, K. Haga, M. Hagiwara, K. Hara, K. Harada, N. Higashi, T. Honda, Y. Honda, T. Honma, M. Hosumi, E. Kako, Y. Kamiya, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, T. Konomi, H. Matsumura, S. Michizono, C. Mitsuda, T. Miura, T. Miura, T. Miyajima, Y. Morikawa, S. Nagahashi, H. Nakai, N. Nakamura, K. Nakanishi, K.N. Nigorikawa, T. Nogami, T. Obina, F. Qiu, H. Sagehashi, M. Shimada, H. Shimizu, T. Shioya, M. Tadano, T. Takahashi, R. Takai, H. Takaki, O.A. Tanaka, Y. Tanimoto, A. Toyoda, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, M. Yamamoto
    KEK, Ibaraki, Japan
  • R. Hajima, K. Kawase
    QST, Tokai, Japan
  • N.P. Norvell
    SLAC, Menlo Park, California, USA
  • F. Sakamoto
    Akita National College of Technology, Akita, Japan
  • M. Shimada
    HSRC, Higashi-Hiroshima, Japan
  Funding: Supported by Accelerator Inc. and a New Energy and Industrial Technology Development Organization (NEDO) project and JSPS Grant-in-Aid for Scientific Research (KAKENHI) Grant Number JP18H03473.
A superconducting Compact Energy Recovery Linac (cERL) for electrons was constructed in 2013 at KEK to demonstrate energy recovery concept with low emittance, high-current CW beams of more than 10 mA for future multi-GeV ERL. Recently this cERL was operated not only to demonstrate energy recovery linac high current beam operation but also to promote and conduct a variety of industrial applications such as FEL, THz operation and Rare Isotope Production and irradiation for some materials. In this talk, I will present the status of the studies to realize the stable high-current low emittance CW beam and some applications with this beam.
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DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-THOTEV02  
About • Received ※ 19 June 2021 — Revised ※ 13 March 2022 — Accepted ※ 13 May 2022 — Issue date ※ 15 May 2022
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THOTEV03 Progress of Recent SRF Activities in India 899
  • P. Shrivastava
    RRCAT, Indore (M.P.), India
  • S. Krishnagopal
    BARC, Mumbai, India
  • P.N. Prakash
    IUAC, New Delhi, India
  • S. Som
    VECC, Kolkata, India
  Funding: Department of Atomic Energy, India
This talk is a summary talk of the recent progress of SRF activities in India including RRCAT, BARC, VECC, IUAC. The latest SRF activities for several national accelerator projects and international projects like PIP-II in FNAL are presented. RRCAT in Indore has been pursuing a complete chain of fabrication, RF tests and characterization at various stages including the SCRF infrastructure facilities, processing, HPR, vertical test stand and Horizontal Test Stand. Several cavities have been successfully tested in the vertical test stand and the Horizontal Test Stand has been commissioned and ready to test the cavities. BARC in Mumbai has developed low beta single spoke cavities for PIP-II R & D in collaboration with IUAC. VECC is pursuing development of single cell and five cell low beta SCRF cavities for PIP-II R &D. IUAC in New Delhi have developed SRF cavities in their infrastructure facilities and has supported institutes in India towards 1.3 GHz cavities, single cell LB and HB cavities and development of SSR1 cavities. Status of the SRF cavity development and the latest results of cavity performance qualification should be presented in this talk
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-THOTEV03  
About • Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 26 February 2022 — Issue date ※ 26 November 2022
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Fundamental Power Couplers and HOM Couplers for High Intensity Application  
  • W. Xu
    BNL, Upton, New York, USA
  Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
High current beams are at the basis of cutting-edge accelerator science and are required in various applications, such as election-ion colliders (EIC), accelerator-driven systems (ADS) and high power Free Electron Lasers (FEL). The RF challenges for these applications are high RF power coupler to deliver RF energy to beam and high power HOM coupler to take the unwanted HOM power out of a SRF cavity. This presentation will overview the high power FPCs and HOM couplers in high-current, high power accelerator applications around the world. Detailed consideration of BNL’s effort on design, manufacture and test 500 kW, 591 MHz input power couplers and 20 kW higher order mode absorbers for the EIC SRF systems will be shown. Both of these high power applications extend current performance of this type of hardware in power handling and size. The design motivations inherent to the EIC SRF, how these devices address the EIC-SRF requirements and current prototype testing results will be presented in this talk.
slides icon Slides THOTEV04 [5.722 MB]  
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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, Meyrin, 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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THOTEV06 Plasma Electrolytic Polishing as a Promising Treatment Replacement of Electropolishing in the Copper and Niobium Substrate Preparation for SRF 718
  • C. Pira, O. Azzolini, R. Caforio, E. Chyhyrynets, V.A. Garcia, G. Keppel, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  Superconducting radio frequency (SRF) cavities performances strongly depend on the substrate preparation. Currently, the conventional protocol of SRF surface preparation includes electropolishing (EP) as the main treatment achieving low roughness, clean and non-contaminated surfaces, both for bulk Nb and Cu substrates. Harsh and non-environmentally friendly solutions are typically used: HF and H2SO4 mixture for Nb, and H3PO4 with Butanol mixtures for EP of Cu. This research is focused on the application of a relatively new technique "Plasma Electrolytic Polishing" (PEP) for the SRF needs. PEP technology is an evolution of EP with a list of advantages that SRF community can benefit from. PEP requires diluted salt solutions moving to a greener approach in respect to EP. PEP can in principle substitute, or completely eliminate, intermediate steps, like mechanical and/or (electro) chemical polishing. Thanks to the superior removing rate in the field (up to 3.5 µm/min of Nb, and 10 µm/min of Cu) in one single treatment roughness below 100 nm Ra has been obtained both for Nb and Cu. In the present work a proof of concept is shown on Nb and Cu planar samples.  
slides icon Slides THOTEV06 [7.202 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-THOTEV06  
About • Received ※ 21 June 2021 — Accepted ※ 18 October 2021 — Issue date ※ 01 May 2022  
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THOTEV07 Industrial X-Ray Tomographie as a Tool for Shape and Integrity Control of SRF Cavities 725
  • H.-W. Glock, J. Knobloch, A. Neumann, A. Veléz
    HZB, Berlin, Germany
  Industrial X-ray tomography offers the possibility to capture the entire inner and outer shape of an SRF cavity, providing also insights in weld quality and material defects. As a non-contact method this is especially attractive to investigate shape properties of fully processed and closed cavities. A drawback is the inherently strong X-ray damping of niobium, which causes the demand for intense hard X-rays, typically beyond the capabilities of dc-X-ray-tubes. This also limits the accuracy of material borders found by the tomographic inversion. To illustrate both capabilities and limitations, results of X-ray tomography investigations using three different cavities are reported, also describing the fundamental parameters and the hard- and software demands of the technology. We also discuss the non-trivial transferring of tomography data into RF simulation tools.  
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slides icon Slides THOTEV07 [9.705 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-THOTEV07  
About • Received ※ 30 June 2021 — Revised ※ 03 January 2022 — Accepted ※ 03 March 2022 — Issue date ※ 08 April 2022
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LCLS-II HE R&D Collaboration Overview  
  • M. Martinello
    Fermilab, Batavia, Illinois, USA
  This talk will present an overview of the LCLS-II HE R&D programs carried in collaboration between SLAC, Fermilab and Jlab in order to develop a new N-doping recipe and cavity processing protocol to meet the new challenging specifications and optimize flux expulsion management. Performance of the first set of cavities will be discussed comparing results from the vertical test to the cryomodule. Different aspects studied in detail during the verification cryomodule (vCM) test such as, multipacting processing optimization, Q-factor quench degradation and plasma processing will be discussed in this talk.  
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