Author: Umemori, K.
Paper Title Page
TUCOYBS01
 KEK ERL SRF Operation Experience  
 
  • H. Sakai, T. Furuya, E. Kako, T. Konomi, T. Miura, F. Qiu, K. Umemori
    KEK, Ibaraki, Japan
  
  We will present the SRF operation experience during long-term cERL operation in KEK.  
slides icon Slides TUCOYBS01 [8.289 MB]  
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TUCOZBS04 Characterization of Microphonics in the cERL Main Linac Superconducting Cavities 48
 
  • F. Qiu, D.A. Arakawa, M. Egi, E. Kako, H. Katagiri, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • M. Egi, S. Michizono
    Sokendai - Hayama, Hayama, Japan
  • E. Kako, T. Konomi, T. Matsumoto, T. Miura, F. Qiu, H. Sakai, K. Umemori
    Sokendai, Ibaraki, Japan
  
  In the main linac (ML) of the KEK-cERL, two superconducting cavities with high loaded Q (QL ¿ 1×107) are operated in continuous wave (CW) mode. It is important to control and suppress the microphonics detuning owing to the low bandwidth of the cavities. We evaluated the background microphonics detuning by the low level radio frequency system during the beam operation. Interestingly, a ¿field level dependence microphonics¿ phenomenon was observed on one of the cavities in the ML. Several frequency components were suddenly excited if the cavity field is above a threshold field (~3 MV/m). We found that this threshold field is probably related with the cavity quench limits despite the unclear inherent physical mechanism. Furthermore, in order to optimize the cavity resonance control system for better microphonics rejection, we have measured the mechanical transfer function between the fast piezo tuner and cavity detuning. Finally, we validated this model by comparing the model response with actual system response.  
slides icon Slides TUCOZBS04 [7.564 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-TUCOZBS04  
About • paper received ※ 13 September 2019       paper accepted ※ 01 November 2019       issue date ※ 24 June 2020  
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THCOXBS02 Development of HOM Coupler with C-Shaped Waveguide for ERL Operation 138
 
  • M. Sawamura, R. Hajima
    QST, Tokai, Japan
  • M. Egi, K. Enami, T. Furuya, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  
  HOM damping in the superconducting cavities has been becoming increasingly important for high current beam acceleration. Though some HOM damping devices have already been used with success at moderate currents, they have some inherent disadvantages for high current in principle. We have proposed the new type of the HOM coupler using the C-shaped wave guide (CSWG). The CSWG is structured by topologically transforming a rectangular waveguide into coaxial-like structure whose inner and outer conductors are connected with a plate. Similar to the rectangular waveguide, the CSWG has cutoff frequency whose half wave length is approximately equal to the mean circumference. This enables a smaller low-pass filter than the rectangular waveguide. Since the inner conductor can be easily cooled through the plate and the outer conductor, this prevents the connector for HOM power extraction from temperature rising. These characteristics of the CSWG-type HOM coupler can solve the disadvantages of the conventional damping devices. The properties of sufficient HOM damping were confirmed by the measurements with the CSWG-type HOM couplers equipped to the cavity models.  
slides icon Slides THCOXBS02 [7.418 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ERL2019-THCOXBS02  
About • paper received ※ 13 September 2019       paper accepted ※ 01 November 2019       issue date ※ 24 June 2020  
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