Author: Tamashevich, Y.
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MOPTEV006 Synchrotron XPS Study of Niobium Treated with Nitrogen Infusion 211
  • A.L. Prudnikava, J. Knobloch, O. Kugeler, Y. Tamashevich
    HZB, Berlin, Germany
  • V. Aristov, O. Molodtsova
    DESY, Hamburg, Germany
  • S. Babenkov
    LIDYL, Gif sur Yvette, France
  • A. Makarova
    FUB, Berlin, Germany
  • D. Smirnov
    Technische Universität Dresden, Dresden, Germany
  Processing of niobium cavities with the so-called ni-trogen infusion treatment demonstrates the improve-ment of efficiency and no degradation of maximal accelerating gradients. However, the chemical compo-sition of the niobium surface and especially the role of nitrogen gas in this treatment has been the topic of many debates. While our study of the infused niobium using synchrotron X-ray Photoelectron Spectroscopy (XPS) showed modification of the surface sub-oxides surprisingly there was no evidence of nitrogen con-centration build up during the 120°C baking step, irre-spectively of N2 supply. Noteworthy, that the niobium contamination with carbon and nitrogen took place during a prolonged high-temperature anneal even in a high vacuum condition (10-8-10-9 mbar). Evidently, the amount of such contamination appears to play a key role in the final cavity performance  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV006  
About • Received ※ 21 June 2021 — Revised ※ 13 July 2021 — Accepted ※ 19 August 2021 — Issue date ※ 05 September 2021
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MOPTEV007 RF Conditioning of 120 kW CW 1.3 GHz High Power Couplers for the bERLinPro Energy Recovery Linac 216
  • A. Neumann, W. Anders, A. Frahm, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich
    HZB, Berlin, Germany
  Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
This year, the commissioning of the 50 MeV, 100 mA bERLinPro Energy Recovery Linac test facility [1] will resume. For the Booster cryo-module of the injector line, operated with three modified 1.3 GHz Cornell style 2-cell SRF cavities, a new type of power coupler was developed, based on KEK’s C-ERL injector coupler. Modifications were made for a stronger coupling and lower emittance diluting coupler tip variant, a so-called "Golf Tee" shape and the cooling concept was redesigned based on KEK’s first experiences. For the final stage, the injector needs to deliver a low emittance beam of 100 mA average beam current at 6.5 MeV. That results in a traveling and continuous wave forward power requirement of up to 120 kW each of the twin setup feeding one Booster cavity. In this contribution we will give a short overview of the RF design and its impact on the beam’s emittance, give an overview of the conditioning teststand and the results achieved with the first pairs of couplers.
[1] M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034
poster icon Poster MOPTEV007 [2.466 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV007  
About • Received ※ 19 June 2021 — Accepted ※ 19 August 2021 — Issue date ※ 17 January 2022  
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WEPCAV010 Comparison of Electromagnetic Properties During Fabrication of Copper and Niobium Prototypes of 325 MHz Coaxial Half-Wave Resonator 609
  • D. Bychanok, V. Bayev, S. Huseu, S.A. Maksimenko, A.E. Sukhotski, E. Vasilevich
    INP BSU, Minsk, Belarus
  • A.V. Butenko, E. Syresin
    JINR, Dubna, Moscow Region, Russia
  • M. Gusarova, M.V. Lalayan, S.M. Polozov
    MEPhI, Moscow, Russia
  • V.S. Petrakovsky, A.I. Pokrovsky, A. Shvedov, S.V. Yurevich
    Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
  • Y. Tamashevich
    HZB, Berlin, Germany
  The main fabrication stages of niobium and copper prototypes of coaxial half-wave resonators (HWR) operating at frequency 325 MHz for the Nuclotron-based Ion Collider fAcility (NICA) injector are presented and discussed. Results of intermediate measurements and electromagnetic properties control for niobium and copper cavities of equivalent geometrical characteristics are compared and analyzed. The comparison of electromagnetic properties of Cu- and Nb-prototypes allows estimating specific features and differences of intermediate "warm" measurements of niobium and copper cavities. The presented results will be used for further development and production of superconductive niobium cavities with a similar design for the NICA-project.  
poster icon Poster WEPCAV010 [3.185 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV010  
About • Received ※ 21 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 27 December 2021 — Issue date ※ 05 May 2022
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WEPTEV003 A Superconducting Magnetic Shield for SRF Modules with Strong Magnetic Field Sources 637
  • J. Völker, A. Frahm, S. Keckert, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, Y. Tamashevich
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  Frequently SRF modules require strong focusing magnets close to SRF cavities. The shielding of those magnetic fields to avoid flux trapping, for example during a quench, is a challenge. At HZB, the bERLinPro photo-injector module includes a 1.4 cell SRF cavity placed in close proximity to a superconducting (SC) focusing solenoid. At full solenoid operation, parts of the double mu-metal shield are expected to saturate. To prevent saturation, we developed a new superconducting Meissner-Shield. Several tests of different designs were performed both in the injector module and in the HoBiCaT test facility. The measured results of the final design show a significant shielding that are in good agreement with calculations. Based on these results, a reduction of the magnetic flux density in the mu-metal shields of almost one order of magnitude is expected The design has now been incorporated in the injector module. In this paper we will present the design, the setup and results of the final testing of the superconducting shield.  
poster icon Poster WEPTEV003 [1.859 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV003  
About • Received ※ 21 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 15 March 2022
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Damage Recovery for SRF Photoinjector Cavities  
  • Y. Tamashevich, A. Frahm, F. Göbel, S. Heling, A. Hellwig, K. Janke, S. Klauke, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, A.L. Prudnikava, S. Rotterdam, M. Schuster, J. Ullrich
    HZB, Berlin, Germany
  Two niobium elliptical 1.3 GHz SRF electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both injector cavities had deep imprints in critical high surface electric field area around the photoelectric cathode position. The repairing procedure, consisting of surface inspection, mechanical polishing and light chemical etching is described in detail. Subsequent cold RF tests demonstrate complete performance recovery.  
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