• 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.

• 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.

• 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.