Author: Yamamoto, Y.
Paper Title Page
MOP077 Ceramic Study on RF Windows for Power Coupler, Waveguide, and Klystron in Particle Accelerator 255
  • Y. Yamamoto, S. Michizono
    KEK, Ibaraki, Japan
  R&Ds on different types of ceramic used in power coupler, waveguide, and klystron for particle accelerators are under progress in Center of Innovation (COI) at KEK, and at some outside companies. There are five important parameters on the properties of ceramics; that is, relative permittivity, dielectric loss tangent, surface and volume resistivity, and secondary electron emission coefficient. For measurements of these parameters, eight kinds of ceramic samples supplied from five vendors have been measured using three different measurement systems since 2017. In this report, the recent results for these studies will be presented in detail.  
DOI • reference for this paper ※  
About • paper received ※ 22 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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MOP083 R&D of Copper Electroplating Process for Power Couplers: Effect of Microstructures on RRR 278
  • Y. Okii, J. Taguchi
    Nomura Plating Co, Ltd., Osaka, Japan
  • E. Kako, S. Michizono, Y. Yamamoto
    KEK, Ibaraki, Japan
  • H. Takahashi, H. Yasutake
    CETD, Tochigi, Japan
  Power couplers for superconducting cavities are required to have both low-thermal conductivity and high-electrical conductivity, because high-thermal conductivity and low-electrical conductivity could generate unexpected increase for heat load. In order to combine these contrary properties, power couplers are made of stainless steel and plated with copper plating. As electrical conductivity of copper layer affects dynamic heat load, it is crucial to optimize plating processes. In this study, we investigated influences of plating parameters (i.e., thickness of copper layer, plating bath composition, bath temperature, heat-treatment conditions) on RRR by collaborative work among Nomura plating, CETD, and KEK. As a result, we obtained high-RRR samples with conditions noted below; (1) electroformed copper plate, (2) copper layer thickness of over 50 µm, and (3) heat-treatment at 200deg-1h, (4) other plating bath composition. In addition, we observed microstructures of several samples, then found that microstructures of copper layer are strongly related to RRR. In this paper, we will present the recent results for this investigation.  
DOI • reference for this paper ※  
About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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TUP104 Improvement of a Clean Assembly Work for Superconducting RF Cryomodule and Its Application to the KEK-STF Cryomodule 721
  • H. Sakai, E. Kako, T. Konomi, K. Umemori, Y. Yamamoto
    KEK, Ibaraki, Japan
  • T. Ebisawa, A. Kasugai
    QST, Aomori, Japan
  We usually encountered the degradation of the superconducting RF cavities on the cryomodule test even though the performance of these cavities was good on the vertical test. In reality, the degradation of Q-values of two cavities of cERL main-linac were observed after cryomodule assembly in KEK [1] and STF cryomodule also met the degradation after the cryomodule assembly [2]. Some dusts and invisible particles might enter the cavity and generate field emission during the assembly work. Field emission is the most important cause of this degradation. In this paper, first we introduce some trials for the improved clean assembly work to SRF cavity by re-examining our clean assembly work and vacuum work. For example, slow pumping system with vacuum particle monitor was developed to know and control the particle movement during slow pumping and venting. Next we show the application of this improved work to the STF re-assemble cryomodule work in KEK.
[1} H. Sakai et al., SRF’13, Paris, France, p.855, 2013.
[2] Y. Yamamoto et al., IPAC’16, Busan, Korea, p.2158, 2016.
DOI • reference for this paper ※  
About • paper received ※ 20 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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Successful Beam Commissioning in STF-2 Cryomodules for ILC  
  • Y. Yamamoto, M. Akemoto, D.A. Arakawa, S. Araki, A. Aryshev, M. Egi, M.K. Fukuda, K. Hara, H. Hayano, Y. Honda, T. Honma, E. Kako, H. Katagiri, M. Kawamura, N. Kimura, Y. Kojima, Y. Kondou, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, T. Miyajima, Y. Morikawa, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, T. Obina, T. Oyama, F. Qiu, T. Saeki, H. Sakai, T. Sanami, M. Shimada, H. Shimizu, T. Shishido, S.I. Takahara, K. Umemori, A. Yamamoto
    KEK, Ibaraki, Japan
  • M. Kuriki, S. Notsu
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  • S. Matsuba
    JASRI, Hyogo, Japan
  • K. Sakaue
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  Beam commissioning of the STF-2 accelerator was successfully done at the Superconducting RF Test Facility (STF) in KEK from February to March 2019. As a result of various cavity tuning, LLRF control tuning, and beam tuning, the beam energy finally reached 271 MeV, and the accelerating gradient of each cavity estimated from beam energy was 32.0 MV/m. This result satisfies 31.5 MV/m, which is the operating specification of the International Linear Collider (ILC) project, and is an important milestone in the ILC technology demonstration. In this talk, we will report on the detailed results of beam commissioning.  
slides icon Slides WETEA6 [13.702 MB]  
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