Keyword: impedance
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MOP070 Investigation of the Critical RF Fields of Superconducting Cavity Connections cavity, simulation, vacuum, niobium 230
  • J.C. Wolff, J.I. Iversen, D. Klinke, D. Kostin, D. Reschke, S. Sievers, A. Sulimov, J.H. Thie, M. Wiencek
    DESY, Hamburg, Germany
  • R. Wendel, J.C. Wolff
    HAW Hamburg, Hamburg, Germany
  To optimise the length of the drift tube of a superconducting cavity (SC), it is required to know the critical value of the RF fields to prevent a potential early quench at the flange connection in case of a drift tube length reduction. To avoid changes on the SC which has been used for the tests, all RF cryogenic experiments have been carried out by using a cylinder in the center of a 1-cell cavity drift tube to increase the field magnitude at the connection. This cylinder has been designed and optimised by RF simulations to provide a field density at the connection twice as high as at a chosen reference point near the iris. Hence also a test SC with a comparatively low gradient can be used without causing field restrictions. In this contribution an approach to investigate the field limitations of 1.3 GHz TESLA-Shape SC connections and thereby the minimal drift tube length based on simulations will be presented.  
DOI • reference for this paper ※  
About • paper received ※ 23 June 2019       paper accepted ※ 04 July 2019       issue date ※ 14 August 2019  
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THP010 The Mechanism of Electropolishing of Niobium from Choline Chloride-based Deep Eutectic Solvents ECR, polarization, niobium, cavity 852
  • Q.W. Chu, H. Guo, S.C. Huang, A.D. Wu, Z.M. You
    IMP/CAS, Lanzhou, People’s Republic of China
  Funding: National Natural Science Foundation (11705252)
The mechanism of electropolishing of niobium (Nb) from choline chloride-based deep eutectic solvent (DES) was studied by anodic polarization tests and electrochemical impedance spectroscopy (EIS) using a Nb rotating disk electrode (RDE). Based on the results of an anodic polarisation test, the electropolishing of Nb is mass transport controlled. EIS results are consistent with the compact salt film mechanism for niobium electropolishing in this electrolyte. The influence of rotation rate, applied potential and electrolyte temperature on the electropolishing mechanism of Nb was investigated. As the applied potential positively shift, Rct, Rp and L increase, CPE decrease and Rs unchanged. The increase in rotation rate and electrolyte temperature leads to a decrease of Rs, Rct, Rp and L, and an increase of CPE.
DOI • reference for this paper ※  
About • paper received ※ 18 June 2019       paper accepted ※ 02 July 2019       issue date ※ 14 August 2019  
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