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Fukami, K.

Paper Title Page
WEPC076 Remote Tilt-control System of Injection Bump Magnet in the SPring-8 Storage Ring 2172
 
  • K. Fukami, C. Mitsuda, M. Oishi, M. Shoji, K. Soutome, H. Yonehara, C. Zhang
    JASRI/SPring-8, Hyogo-ken
  • M. Hasegawa, T. Nakanishi
    SES, Hyogo-pref.
  • T. Ohshima
    RIKEN/SPring-8, Hyogo
 
  The SPring-8 storage ring has four pulse-bump magnets to generate bump orbit for beam injection. Rotational error of the bump magnets around a beam-axis (tilt) induces the stored-beam oscillation in vertical direction due to horizontal error field. In the top-up operation, vertical perturbation of the stored-beam during beam injection is mainly produced by the tilt. We evaluated the tilt angle by measuring of the perturbation turn-by-turn using a single-pass BPM system and realigned bump magnets manually inside the accelerator tunnel. It was required to repeat the measurement and realignment processes two or three times for convergence. To correct the tilts smoothly, we developed a remote tilt-control system. The system consists of two fixed and one movable supports in vertical direction under each bump magnets. The movable support is driven by a stepper motor through 1/30 worm gear in the range of ±4 mrad with the accuracy of less than 0.1 mrad. By using this system, we succeeded complete on-beam reduction of the perturbation.  
THPC070 Symmetry Restoration of the SPring-8 Storage Ring by Counter-sextupole Magnets 3149
 
  • K. Soutome, S. Daté, T. Fujita, K. Fukami, C. Mitsuda, A. Mochihashi, H. Ohkuma, M. Oishi, S. Sasaki, J. Schimizu, Y. Shimosaki, M. Shoji, M. Takao, K. Tsumaki, H. Yonehara, C. Zhang
    JASRI/SPring-8, Hyogo-ken
  • S. Matsui, H. Takebe, H. Tanaka
    RIKEN/SPring-8, Hyogo
 
  In the SPring-8 storage ring there are four magnet-free long straight sections of about 30m. These were realized in 2000 by locally rearranging quadrupole and sextupole magnets. In modifying the optics we took care of the periodicity of cell structure, especially of sextupole field distribution along the ring. To keep the periodicity high and hence the dynamic aperture large, we adopted a scheme in which "betatron phase matching" and "local chromaticity correction" are combined. In this scheme the dynamic aperture for on-momentum electrons is kept by the phase matching and that for off-momentum electrons is enlarged by the local chromaticity correction with weak sextupoles (SL). After modifying the lattice, we tried to recover the symmetry of the ring further and found that a harmful effect of nonlinear kick due to SL can be minimized by additional "counter-sextupole magnets" placed 180 degrees apart in horizontal betatron phase from SL. We installed such counter-sextupoles in every long straight sections and confirmed that the aperture was improved. In the paper we discuss these topics showing experimental data of injection efficiency, momentum acceptance, etc.  
THPC127 Filling of High Current Singlet and Train of Low Bunch Current in SPring-8 Storage Ring 3284
 
  • T. Nakamura, T. Fujita, K. Fukami, K. Kobayashi, C. Mitsuda, M. Oishi, S. Sasaki, M. Shoji, K. Soutome, M. Takao, Y. Taniuchi
    JASRI/SPring-8, Hyogo-ken
  • T. Ohshima
    RIKEN/SPring-8, Hyogo
  • Z. R. Zhou
    USTC/NSRL, Hefei, Anhui
 
  We performed the storage of high current singlet of 10mA/bunch and a train of bunches of 0.3mA/bunch under the bunch by bunch feedback systems with newly developed bunch current sensitive automatic attenuators with FPGA. The automatic attenuator reduces the signal level of the high current bunch by factor three to five to avoid the saturation of the feedback systems. With this system, the feedback systems suppress horizontal and vertical mode-coupling instabilities and raise the bunch current limit from 3.5mA/bunch to 12mA/bunch, and simultaneously the systems suppress the multi-bunch instabilities by resistive-wall and cavity higher order mode impedances. The improvement of the automatic attenuation system to fit to the final target of the bunch current in the train, 0.06mA/bunch, are being performed. The other problems which limit the filling patterns, such as saturation of the readout electronics of the beam position monitor system and the heating of vacuum components by high current bunches, will be briefly presented.  
THPC146 Beam Halo Monitor Using Diamond Detectors for XFEL/SPring-8 3330
 
  • H. Aoyagi, Y. Asano, T. Bizen, K. Fukami, N. Nariyama
    JASRI/SPring-8, Hyogo-ken
  • T. Itoga, H. Kitamura, T. Tanaka
    RIKEN/SPring-8, Hyogo
 
  The construction of the XFEL facility at SPring-8 has been started. We have been developing a halo monitor as an interlock device for protection of undulator permanent magnets against radiation damage. When permanent magnets are irradiated with a halo part of 8GeV electron beam, magnetic fields are degraded permanently and laser oscillation is weakened. Therefore, the interlock device is required during machine operation. Diamond detector, which operates in photoconductive mode, is good candidate for electron beam sensor. The beam test of the diamond detector head has been carried out at the beam dump of the SPring-8 booster synchrotron. Minimum number of injected electron was about 1·105 /pulse, and we observed the pulse height of 0.1V having the pulse length of 0.6nsec FWHM without a preamplifier. The linearity of output signal on injected beam was also demonstrated. The beam halo monitor equipped with the diamond detectors is under manufacturing. The design and feasibility tests will be presented in this conference.