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Torikai, K.

Paper Title Page
TPAT096 Focusing-Free Transition Crossing in RHIC using Induction Acceleration 4314
 
  • K. Takayama, Y. Shimosaki, K. Torikai
    KEK, Ibaraki
  • J. Wei
    BNL, Upton, Long Island, New York
 
  Focusing-free transition crossing (FFTC) in RHIC is proposed. The original idea of FFTC proposed by J.Griffin was tried in the FNAL 500GeV main ring, where a gradient in the acceleration voltage was smoothed flat by introducing multi higher-harmonic RF. If the longitudinal focusing disappears during a limited time period near TC, various undesired features, such as bunch shortening and elongation in the momentum space, should be mitigated. In present RHIC operation, the slow ramping across transition leads into complications of nonlinear chromatic effects, vacuum pressure rise, instability, and transition-jump related lattice distortions. Recently, induction acceleration of a single RF bunch has been successfully demonstrated in KEK-PS,* where a proton bunch is trapped by the existing RF and accelerated with an induction step-voltage to 8 GeV. The utilized acceleration device is capable of generating a step voltage of 2 kV/cell at most at an arbitrary repetition rate up to 1 MHz. We here propose focusing-free TC in RHIC, introducing similar devices. In this scheme, the RF voltage is tuned off during an optimized time-period of several tens of ms, and the required acceleration voltage is provided as an induction flat-voltage.

*K.Takayama et al., submitted to Phys. Rev. Lett., http://www.arxiv.org/pdf/physics/0412006.

 
TPPT014 Induction System for a Proton Bunch Acceleration in Synchrotron 1398
 
  • K. Torikai, Y.A. Arakida, J. Kishiro, T. Kono, E. Nakamura, Y. Shimosaki, K. Takayama, T. Toyama, M. Wake
    KEK, Ibaraki
 
  Funding: The project is officially supported by Grant-In-Aid for Creative Scientific Research (KAKENHI 15GS0217, 5 years term).

An induction cavity capable of operating at a repetition rate of 1MHz with a 50% duty has been built and employed for the first induction acceleration of a proton bunch from 500MeV to 8GeV in the KEK-PS.* In this experiment, an acceleration voltage of 4.7kV and an repetition frequency of 667kHz-882kHz were required. The installed induction device consists of three induction cells, each of which can generate a bipolar induction voltage of a maximum output voltage of 2 kV with a flat-top of 300ns and a 25ns rising/falling time. Electrical characteristics of the cavity itself, such as inductance, capacitance, and resistance, have been evaluated in three independent ways: (1) excitation due to a small signal from a network analyzer, (2) excitation by a proton beam as a primary driver, (3) excitation with a actual pulse modulator in an entire system. This paper will compare these results as well as theoretical design values. A general design procedure for an induction acceleration cavity will be given.

*K.Takayama et al., submitted to Phys. Rev. Lett. http://www.arxiv.org/pdf/physics/0412006.

 
FPAE020 Induction Acceleration of a Single RF Bunch in the KEK PS 1679
 
  • K. Takayama, D.A. Arakawa, Y.A. Arakida, S. Igarashi, T. Iwashita, T. Kono, E. Nakamura, M. Sakuda, H. Sato, Y. Shimosaki, M.J. Shirakata, T. Sueno, K. Torikai, T. Toyama, M. Wake, I. Yamane
    KEK, Ibaraki
  • K. Horioka
    TIT, Yokohama
  • A.K. Kawasaki, A. Tokuchi
    NICHICON, Shiga
  • J. Kishiro
    JAERI/LINAC, Ibaraki-ken
  • K. Koseki
    GUAS/AS, Ibaraki
  • M.S. Shiho
    JAERI/NAKA, Ibaraki-ken
  • M. Watanabe
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
 
  A single bunch trapped in an RF bucket was accelerated by induction devices from 500 MeV to 8GeV beyond transition energy in the KEK-PS. This is the first demonstration of induction acceleration in a high energy circular ring. The acceleration was confirmed by measuring a temporal evolution of the RF phase through an entire acceleration.* Key devices in an induction acceleration system are an induction accelerating cavity capable of generating an induced voltage of 2kV/cell, a pulse modulator to drive the cavity (switching driver), and a DSP system to control gate signals for switching. Their remarkable characteristics are its repetition ratio of about 1MHz and duty factor of 50%. All devices have been newly developed at KEK so as to meet this requirement. The pulse modulator employing MOSFETs as switching elements is connected with the accelerating cavity through a long transmission cable in order to avoid a high-dose irradiation in the accelerator tunnel. The induction system has been running beyond more than 24 hours without any troubles. The paper will take an introductive role for related other 6 papers too, which describe more technical aspects and novel beam physics associated with the induction acceleration.

*K.Takayama et al., submitted to Phys. Rev. Lett., http://www.arxiv.org/pdf/physics/0412006.