Author: Sievers, S.
Paper Title Page
MOPO037 SRF Gun Development at DESY 105
MOOP07   use link to see paper's listing under its alternate paper code  
 
  • E. Vogel, S. Barbanotti, I. Hartl, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, M. Schmökel, J.K. Sekutowicz, S. Sievers, N. Steinhau-Kühl, A.A. Sulimov, J.H. Thie, H. Weise, L. Winkelmann, B. van der Horst
    DESY, Hamburg, Germany
  • J.A. Lorkiewicz, R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  • J. Teichert
    HZDR, Dresden, Germany
  • M. Wiencek
    IFJ-PAN, Kraków, Poland
 
  A future upgrade of the European XFEL (E-XFEL) foresees an additional cw operation mode increasing the flexibility in the photon beam time structure. This mode requires among others a cw operating photo injector. We believe that using an SRF gun is the preferred approach as the beam parameters of normal conducting pulsed guns can be potentially met by SRF guns operating cw. Since more than a decade DESY in collaboration with TJNAF, NCBJ, BNL, HZB and HZDR performs R&D to develop an all superconducting RF gun with a lead cathode. In the frame of E-XFEL cw upgrade feasibility studies, the SRF-gun R&D program gained more attention and support. Within the next few years we would like to demonstrate the performance of the all superconducting injector required for the E-XFEL upgrade. The selected approach offers advantages w.r.t. the cleanliness of the superconducting surface, but requires a complete disassembly of a cryostat and stripping the gun cavity in a clean room to exchange the cathode. Thus it is practical only when the life time of the cathode is at least several months. In this paper we present the actual status of the R&D program, next steps and the longer term plans.  
slides icon Slides MOPO037 [1.966 MB]  
poster icon Poster MOPO037 [3.774 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO037  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TUPO028 Retreatment of European XFEL Series Cavities at DESY as Part of the Repair of European XFEL Accelerating Modules 384
 
  • S. Sievers, N. Krupka, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, N. Steinhau-Kühl, E. Vogel, H. Weise, B. van der Horst
    DESY, Hamburg, Germany
  • M. Wiencek
    IFJ-PAN, Kraków, Poland
 
  For the European XFEL 102 accelerating modules were built and tested. Several accelerating modules had to be reworked due to different kinds of non-conformities. The extent of this rework varied greatly. At the end of production four accelerating modules could not be qualified in time before the tunnel installation was to be finished in September 2016. Meanwhile the cavity strings of two of these accelerating modules have been disassembled in the DESY clean room. The cavities have been retreated at DESY either by additional high pressure water rinsing or BCP flash chemical treatment. All cavities were vertically tested and 15 out of 16 were qualified for the reassembly of the cavity strings. One accelerating module will be reassembled completely and tested until the end of 2018; the other will follow in the first half of 2019. We report on retreatment procedures and performance of these cavities.  
poster icon Poster TUPO028 [1.662 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO028  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TH2A01 Nitrogen Infusion R&D for CW Operation at DESY 652
 
  • M. Wenskat, A.D. Dangwal Pandey, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise
    DESY, Hamburg, Germany
  • C. Bate, G.D.L. Semione, A. Stierle
    University of Hamburg, Hamburg, Germany
  • B. Foster
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • B. Foster
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
 
  The European XFEL cw upgrade requires cavities with reduced surface resistance (high Q-values) for high duty-cycle while maintaining high accelerating gradient for short-pulse operation. To improve on European XFEL performance, a recently discovered treatment is investigated: The so called Nitrogen-infusion. The recent test results of the cavity based R&D and the progress of the relevant infrastructure is presented. The aim of this approach is to establish a stable, reproducible recipe and to identify all key parameters for this process. In parallel, advanced surface analyses, such as SEM/EDX, TEM, XPS, XRR, GIXRD and TOF-SIMS, of samples after in-situ treatment, cut-outs of cavities and samples treated together with cavities are done. The aim of this approach is to understand the underlying processes of the material evolution, resulting in the improved performance. Results of these analyses, their implications for the cavity R&D, and next steps are presented.  
slides icon Slides TH2A01 [4.597 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TH2A01  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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