• T. Takayanagi, H. Harada, H. Hotchi, Y. Irie, J. Kamiya, M. Kinsho, P.K. Saha, T. Togashi, T. Ueno, M. Watanabe, M. Yoshimoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• K. Satou
  J-PARC, KEK & JAEA, Ibaraki-ken

The painting injection of the 3-GeV RCS in J-PARC has been tested since May in 2008. The shift bump-magnets, which give a constant bump field in a horizontal plane during injection, comprise four magnets connected in series. However, the total integrated magnetic field over the four magnets is not zero because of the magnetic field interferences with the neighboring quadrupole magnets. So the gap of each magnet was adjusted by inserting thin insulators into the splitting plane of the side yoke so that the field integration becomes zero. The thickness was determined experimentally. The closed orbit distortion due to the field imbalances was then confirmed to be less than 1 mm. Another four paint bump-magnets are also necessary to give time-dependent fields. They are connected to their own power supplies, separately. The excitation of each magnet is calibrated by using the beam so that the created bump orbit satisfies the position and inclination at the injection point, and there are no orbit distortions outside the injection area. As for a vertical plane, a vertical paint magnet is located pi-radian upstream of the injection point to control the vertical angle of the beam.

• T. Takayanagi, Y. Irie, J. Kamiya, M. Kinsho, T. Togashi, T. Ueno, M. Watanabe, M. Yoshimoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The main circuit of the switching power supplies for the injection bump system is composed of multiple-connection of the IGBT assemblies. The element of the IGBT assembly, which is the power supply of the shift bump-magnets, is a type of 3300V-1200A and 6 kHz in elementary frequency. The power supply has the output performance of 20 kA / 6.6 kV. The synthetic frequency of the multiple-connection assemblies is over 48 kHz and the tracking error less than 1 % is proved. The beam commissioning test of long-term operation for about three-week was performed. The deviation of the exciting current from the programmed current pattern has been confirmed less than 1%. The peculiar characteristic of the pulse power supply has been obtained by the analysis on the frequency response of the exciting current and the magnetic field. In the FFT analytical result of the magnetic field, the peaks of 48 kHz and its higher harmonics that are related to the switching frequency was observed. The ground loop current and the voltage were also measured.

• P.K. Saha, N. Hayashi, H. Hotchi, K. Yamamoto, M. Yoshimoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• Y. Irie
  KEK, Ibaraki
• T. Toyama
  J-PARC, KEK & JAEA, Ibaraki-ken

The beam loss issues connected to the nuclear scattering together with the multiple Coulomb scattering at the charge-exchange foil during the multi-turn injection has been studied in detail for the RCS (Rapid Cycling Synchrotron) of J-PARC (Japan Proton Accelerator Research Complex). Recently, during the beam commissioning of RCS, some experimental data related to such issue has been taken and thus a comparison of the measured beam loss to the estimated one is reported in this paper. When the beam loss from such a source is unavoidable, a realistic estimation is quite important for a fair design of the injection system and the vicinity in order to reduce especially, the uncontrolled beam loss.

• H. Hotchi, N. Hayashi, Y. Hikichi, S. Hiroki, J. Kamiya, K. Kanazawa, M. Kawase, M. Kinsho, M. Nomura, N. Ogiwara, R. Saeki, P.K. Saha, A. Schnase, T. Shimada, Y. Shobuda, K. Suganuma, H. Suzuki, H. Takahashi, T. Takayanagi, O. Takeda, F. Tamura, N. Tani, T. Togashi, T. Ueno, M. Watanabe, Y. Watanabe, K. Yamamoto, M. Yamamoto, Y. Yamazaki, H. Yoshikawa, M. Yoshimoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• A. Ando
  LASTI, Hyogo
• H. Harada
  Hiroshima University, Graduate School of Science, Higashi-Hiroshima
• K. Hasegawa, Y. Irie, C. Ohmori, M. Yoshii
  KEK, Ibaraki
• K. Satou, Y. Yamazaki
  J-PARC, KEK & JAEA, Ibaraki-ken

The beam commissioning of the J-PARC 3-GeV RCS started in October 2007. The initial machine parameter tuning and underlying beam studies were completed in February 2008 through various beam dynamics measurements, such as optical functions, turn-by-turn beam positions, and transverse and logitudinal beam profiles. Now the RCS is in transition from the first commissioning phase to the next challenging stage and our efforts hereafter will be focused on higher beam power operations. In this paper, we describe experimental results obtained in the high intensity demonstrations in October 2008, together with the corresponding simulation results.

• A. Takagi, Y. Irie, I. Sugai, Y. Takeda
  KEK, Ibaraki

Thick carbon foils (>300 ug/cm²)has been used for stripping of H^- ion beam at the 3GeV Rapid Cycling Synchrotron (3GeV-RCS) of J-PARC, where foils with long lifetime against high temperature >1800 °K are strongly required for efficient accelerator operations. The key parameter to the foil lifetime is foil temperature attained during irradiation. We have recently developed a new irradiation system for lifetime measurement using the KEK 650 keV Cockcroft-Walton accelerator with high current pulsed and dc H^- beam, which can simulate the high-energy depositions upon foils in the RCS. During irradiation tests by this system, the temperature of foil is measured by a thermometer in a dc mode, and by using a photo-transistor in a pulsed mode. This paper describes the pulsed measurements with 5-10 mApeak, 0.1-0.5 msec duration and 25 Hz repetition.