Keyword: injection
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MOP027 Study on Nitrogen Infusion using KEK New Furnace cavity, SRF, accelerating-gradient, vacuum 95
 
  • K. Umemori, E. Kako, T. Konomi, S. Michizono, H. Sakai
    KEK, Ibaraki, Japan
  • T. Okada
    Sokendai, Ibaraki, Japan
  • J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  KEK has been carried out high-Q/high-G R&D, to realize high performance of SRF cavities toward ILC. KEK constructed a new furnace, which is dedicated for N-infusion studies. We performed more than 10 times of N-infusion trials using 1.3 GHz single-cell cavities. Some results showed better Q-values up to high field, however, some results showed degraded Q-E slopes probably due to contamination. Improvement of accelerating gradient is not observed at moment. We have tried to clean the furnace and Nitrogen injection line to reduce the effect of contamination. Details of procedures of N-infusion, results of vertical tests, condition of the furnace including RGA spectrum and Nb sample analysis results are shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP027  
About • paper received ※ 04 July 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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TUFUA5 Recent Development on Nitrogen Infusion Work Towards High Q and High Gradient cavity, SRF, niobium, radio-frequency 355
 
  • P. Dhakal
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A quality factor as high as 2 × 1010 at 1.5 GHz was achieved at a gradient of 35 MV/m by 800 °C annealing and N-infusion at 140 °C. A comparison of the field dependence of the surface resistance after N-infusion with a recent theoretical model that extends the calculation of the BCS surface resistance to high rf fields suggests an increase in the quasiparticles’ relaxation time with increasing infusion temperature, which could be due to a decreasing density of subgap states. Nb coupons treated similarly showed the formation of thicker oxynitride layer on the surface beneath thin dielectric Nb2O5 layer. A plausible explanation for the improved Q0 is that the oxynitride layer on the Nb surface adds additional electron scattering within RF penetration depth.
 
slides icon Slides TUFUA5 [6.077 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUA5  
About • paper received ※ 19 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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THP031 Operation Experience with the LHC ACS RF System cavity, cryomodule, operation, MMI 911
 
  • K. Turaj, L. Arnaudon, P. Baudrenghien, O. Brunner, A.C. Butterworth, F. Gerigk, M. Karppinen, P. Maesen, E. Montesinos, F. Peauger, G.J. Rosaz, E.N. Shaposhnikova, D. Smekens, M. Taborelli, M. Therasse, H. Timko, D. Valuch, N. Valverde Alonso, W. Venturini Delsolaro
    CERN, Meyrin, Switzerland
 
  The LHC accelerating RF system consists of two cryomodules per beam, each containing four single-cell niobium sputtered 400.8 MHz superconducting cavities working at 4.5 K and an average accelerating voltage of 2 MV. The paper summarises the experience, availability and evolution of the system within 10 years of operation. The lessons learned from the successful replacement and re-commissioning of one cryomodule with a spare module, and the recent re-test of the originally installed module on the test stand are also included. Finally, a review of currently launched spare cavity production and long-term developments are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP031  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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