Author: Dewa, H.
Paper Title Page
TUPG06 Development Status of a Stable BPM System for the SPring-8 Upgrade 322
  • H. Maesaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • H. Dewa, T. Fujita, M. Masaki, S. Takano
    JASRI, Hyogo, Japan
  A stable and precise BPM system is necessary for the low-emittance upgrade of SPring-8. Key requirements for the BPM system are: 1) long-term stability to maintain the photon beam direction of the beamline well within the intrinsic photon divergence, 2) single-pass resolution better than 100 μm rms for a 100 pC injected bunch for first turn steering in the beam commissioning, and 3) accuracy better than 100 μm rms with respect to aligned quadrupole and sextupole magnet centers to achieve the design performance of the upgraded ring. To realize the demanded stability, the BPM drift should be reduced to 1 μm level. Therefore, we have been pursuing designs to suppress the thermal deformation of a BPM head and its support and to minimize the drifts of BPM electronics and coaxial cables. The investigation results on causes of drifts of the present SPring-8 BPM system are reflected to the design of the new BPM system. A button-type BPM head has been developed*, which can generate sufficient signal to satisfy the required single-pass resolution. We have also been studying the strategies of the alignment, position survey and electric center calibration of the BPM head better than 100 μm.
* M. Masaki et al., in this conference.
poster icon Poster TUPG06 [5.250 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG06  
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TUPG18 Design Optimization of Button-Type BPM Electrode for the SPring-8 Upgrade 360
  • M. Masaki, H. Dewa, T. Fujita, S. Takano
    JASRI, Hyogo, Japan
  • H. Maesaka, S. Takano
    RIKEN SPring-8 Center, Hyogo, Japan
  The requirements for a BPM system for the SPring-8 upgrade are long-term stability, sufficient signal intensity and high accuracy*. The design of a button-type electrode for the BPM has been optimized from the perspectives of 1) mechanical structure, 2) rf characteristics, 3) thermal issue. We have adopted the electrode structure without a sleeve enclosing the button to maximize the button diameter for the narrow aperture of the vacuum chamber. The absence of an annular slot around the sleeve in a lodging hole for the electrode eliminates the associated beam impedance. To minimize the beam impedance and the trapped mode heating of the electrode, the rf structure has been optimized by 3D electro-magnetic simulations. To suppress the ohmic loss on the button and center pin thermally isolated from the water cooled BPM block, we have selected molybdenum as a material with high electric and thermal conductivities. The reduction of the heating suppresses thermal deformation of the electrode and the BPM block, and improves thermal stability of the BPM system. The mechanical tolerance of the electrode was defined to fit the error budget for the total BPM offset error of 0.1 mm rms.
* H. Maesaka et al., in this conference.
poster icon Poster TUPG18 [1.104 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG18  
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