Author: Schnase, A.
Paper Title Page
WEPPR008 Simulation of Controlled Longitudinal Emittance Blow-up in J-PARC RCS 2952
 
  • M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, F. Tamura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • T. Toyama
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
 
  In the J-PARC RCS, a high intensity beam is prepared for the MR. The longitudinal beam emittance at the RCS extraction should be optimized to avoid beam loss during and after MR injection. In order to match the longitudinal emittance shape between the RCS and the MR, it is desirable to enlarge the longitudinal emittance during the RCS acceleration. We have performed the particle tracking simulation for the controlled longitudinal emittance blow up in the RCS.  
 
MOPPD051 Performance of Resonant Slow Extraction from J-PARC Main Ring 481
 
  • M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nakagawa, K. Okamura, H. Sato, Y. Shirakabe, T. Toyama, E. Yanaoka, M. Yoshii
    KEK, Ibaraki, Japan
  • D. Horikawa
    Sokendai, Ibaraki, Japan
  • K. Mochiki
    Tokyo City University, Tokyo, Japan
  • A. Schnase
    JAEA/J-PARC, Tokai-mura, Japan
 
  Proton beam accelerated by the J-PARC main ring (MR) with an imaginary transition lattice is slowly extracted by a third integer resonant extraction scheme and delivered to the hadron experimental hall. One of the critical issues in the slow extraction from a high intensity proton synchrotron is the inevitable beam loss caused by the extraction process at septum devices. A design with low beam loss (high extraction efficiency) is required to reduce machine damage and radiation exposure during hands-on maintenance. We have designed the slow extraction scheme to obtain high extraction efficiency for the MR lattice. The scheme has a large step size and a small angular spread enabling a hit rate of the beam on the developed thin septum device. Since the first 30 GeV proton beam was successfully delivered to the experimental hall in January 2009, an extremely high extraction efficiency of 99.5% has been achieved by an intensive beam tuning. In this paper, we report details of such performance. We will also describe some schemes to improve the serious spiky spill time structure due to large current ripples from the power supplies for the bending and quadrupole magnets.  
 
THPPC005 Design of Magnetic Alloy Resonant System (MARS) Cavity for J-PARC MR 3278
 
  • C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  The Magnetic Alloy Resonant System (MARS) cavity is a new type of Magnetic Alloy (MA) cavity using an external energy storage system. It is proposed as a back-up system of the present J-PARC high-Q MA cavity using cut cores. MARS consists of un-cut core loaded wideband MA cavities combined with an energy storage system using high-impedance, FT3L, cut cores. The main cavities are water-cooled and already established at J-PARC RCS. The energy storage system will be relatively high-Q (>100) to be stable under heavy beam loading. It also has a higher impedance than the main cavity and is air-cooled. The design of this cavity system will be presented.  
 
THPPC006 Status of the J-PARC Ring RF Systems 3281
 
  • M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda
    KEK, Tokai, Ibaraki, Japan
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  Due to the 11th march earthquakes, J-PARC was forced to stop operation. The restoration is following the schedule so that J-PARC is restarted in December. Before the earthquake, we had considerable success in the 400 kW equivalent proton beam in the RCS. Multi-harmonic RF feedforward was established, which contributes to the reduction of beam loss and stable acceleration in RCS. The MR synchrotron achieved stable 150 kW beam operation for the T2K experiment. This summer, we installed two new RF systems in MR. Eight RF systems in total allow a more stable beam acceleration and flexible bunch shape manipulation. Also, we prepare the RF feedforward to compensate beam loading in MR. To achieve a beam power in excess of 1 MW in MR, it is considered to double the MR repetition rate. We developed an annealing scheme for large magnetic alloy cores while inside a DC B-field that results in higher core impedance, and have succeeded in producing large FT3L cores in this summer. With such cores we can almost double the accelerating voltage without re-designing the existing RF sources. For the near future, we plan to replace the existing RF cavities with upgraded cavities using the FT3L cores.  
 
THPPP082 RF Feedforward System for Beam Loading Compensation in the J-PARC MR 3924
 
  • F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • M. Toda
    KEK/JAEA, Ibaraki-Ken, Japan
 
  For acceleration of high intensity proton beams in the J-PARC MR, beam loading compensation is important. In the MA-loaded RF cavity in the MR, which has a Q-value in the order of 20, the wake voltage consists of the accelerating harmonic (h=9) and the neighbor harmonics (h=8, 10). We employ the RF feedforward method for the beam loading compensation, like in the J-PARC RCS, in which the impedance seen by the beam is greatly reduced by the feedforward. The full-digital feedforward system developed for the MR has a similar architecture to that of the RCS. The system compensates the beam loading of the important three harmonics (h=8, 9, 10). We present the structure of the RF feedforward system. Also, we report the preliminary results of the beam tests.