Author: Reschke, D.
Paper Title Page
SUPFDV001 Update on Nitrogen Infusion Sample R&D at DESY 57
 
  • C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, H. Weise, M. Wenskat
    DESY, Hamburg, Germany
  • B. Foster
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Many accelerator projects such as the European XFEL cw upgrade or the ILC, would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on R\&D using small samples, with the goal of identifying all key parameters of the process and establishing a stable, reproducible recipe. To understand the underlying processes of the surface evolution that give improved cavity performance, advanced surface-analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized and several kinds of samples are analyzed. Furthermore, parameters such as RRR and the surface critical magnetic field denoted as Hc3 have been investigated. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Results of these analyses and their implications for the R\&D on cavities are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV001  
About • Received ※ 22 June 2021 — Accepted ※ 03 January 2022 — Issue date; ※ 27 April 2022  
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SUPTEV006 Commissioning of a Calibration Device for Second Sound Quench Detection 124
 
  • L. Ebeling, D. Reschke, L. Steder
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  An important part of research and development in the field of superconducting radio frequency technology is the quench detection since these breakdowns of superconductivity often limit the cavity performance. Although the second sound based quench detection is widely used, only few studies dealing with its systematic uncertainties exist. Hence, the vertical test stands at the cavity test facility of DESY were extended by calibration device prototypes in order to estimate the accuracy of this method. For the first time at DESY, artificial signals have been generated and reconstructed by heating power film resistors. These second sound signals are determined using noise canceling algorithms and the existing reconstruction software. To evaluate the reconstructed positions, the absolute distance between reconstructed and true coordinates is calculated. Thus, a first uncertainty map of the cavity surface is created to quantify the reconstruction results of actual cavity quenches including systematic effects of the quench positioning like the varying sensor coverage around the cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPTEV006  
About • Received ※ 20 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 20 November 2021 — Issue date ※ 30 April 2022
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SUPTEV009 Development of a New B-Mapping System for SRF Cavity Vertical Tests 137
 
  • J.C. Wolff, A. Gössel, C. Müller, D. Reschke, L. Steder, D. Tischhauser
    DESY, Hamburg, Germany
  • W. Hillert, J.C. Wolff
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the cavity to trapped magnetic flux is mainly determined by the treatment, the geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a so-called B-mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution the design, the development process as well as first performance test results of the B-mapping system are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPTEV009  
About • Received ※ 01 July 2021 — Accepted ※ 31 March 2022 — Issue date; ※ 09 April 2022  
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TUOFDV03 Vacancy-Hydrogen Dynamics and Magnetic Impurities During Mid-T Bake 342
 
  • M. Wenskat, C. Bate, D. Reschke, J. Schaffran, L. Steder, H. Weise
    DESY, Hamburg, Germany
  • C. Bate, G.D.L. Semione, A. Stierle
    University of Hamburg, Hamburg, Germany
  • M. Butterling, E. Hirschmann, M.O. Liedke, A. Wagner
    HZDR, Dresden, Germany
  • J. Cizek
    Charles University, Prague, Czech Republic
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Positron annihilation measurements allow to study the hydrogen interaction with vacancies in a crystal lattice. Furthermore, the 3/2 ratio of the positronium annihilation can be used to identify local magnetic impurities in thin layers. Dynamic studies of these properties in annealing studies up to 300°C will be presented. The discussion is accompanied by X-ray reflectivity studies performed on single crystal samples to study the niobium oxide dissolution. The dynamics of magnetic impurities during a Mid-T bake will be presented, put into the context of cavity studies and a potential link to rf properties will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUOFDV03  
About • Received ※ 23 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 05 December 2021
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TUPTEV011 SRF Accelerating Modules Repair at DESY 508
 
  • D. Kostin, J. Eschke, K. Jensch, N. Krupka, L. Lilje, A. Muhs, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst
    DESY, Hamburg, Germany
 
  Eight SRF cavities assembled in an accelerating module represent a building block of the particle linear accelerator based on TESLA SRF technology. DESY has two machines, European XFEL and FLASH. Both use almost same module and cavity types. During the module assembly many factors can deteriorate the cavity performance and cause a need for a repair action. Currently two European XFEL modules and two FLASH ones underwent reassembly procedures. The repair was not immediately successful on every of these modules and re-iterations did follow. The degradation causes were investigated. SRF modules were tested on both test-stands at DESY: AMTF and CMTB. The results of the described actions are presented and discussed.  
poster icon Poster TUPTEV011 [1.494 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPTEV011  
About • Received ※ 18 June 2021 — Accepted ※ 19 November 2021 — Issue date; ※ 01 February 2022  
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WEPCAV013 Occurring Dependency between Adjustable Coupling and Q0 - Finding and Solving a Problem during Vertical Cavity Testing at DESY 619
 
  • Y.F. Liu, C. Luo
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • D. Reschke, L. Steder, M. Wiencek
    DESY, Hamburg, Germany
 
  In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.  
poster icon Poster WEPCAV013 [1.073 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV013  
About • Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021
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THPFDV001 Status of the New Quadrupole Resonator for SRF R&D 751
 
  • R. Monroy-Villa, W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Gorgi Zadeh, P. Putek
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • M. Lemke, R. Monroy-Villa, D. Reschke, M. Röhling, J.H. Thie
    DESY, Hamburg, Germany
 
  A basic understanding of the properties of SRF samples under surface treatments would aid in the development of consistent theories. To study the RF properties of such samples under realistic superconducting-cavity-like conditions, a test device called Quadrupole Resonator (QPR) was fabricated. In this publication we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB, and its design will allow for testing samples at temperatures between 2 K and 8 K, under magnetic fields up to 120 mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with the commissioning report and the ongoing surface treatment, will be presented.  
poster icon Poster THPFDV001 [1.069 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPFDV001  
About • Received ※ 27 June 2021 — Revised ※ 23 August 2021 — Accepted ※ 23 August 2021 — Issue date ※ 29 April 2022
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