Author: Miura, A.
Paper Title Page
MOPB096 Beam Loss Mitigation in J-PARC Linac after the Tohoku Earthquake 401
  • M. Ikegami, Z. Fang, K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Maruta, A. Miura, J. Tamura, G.H. Wei
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • H. Sako
    JAEA, Ibaraki-ken, Japan
  The beam operation of J-PARC linac was interrupted by the Tohoku earthquake in March 2011. After significant effort for its restoration, we have resumed the beam operation of J-PARC linac in December 2011. After resumption of beam operation, we have been suffering from beam losses which were not observed before the earthquake. Tackling with the beam loss issues, we have been reached the comparable beam power for user operation to the one before the earthquake. In this paper, we present the experience in the beam start-up tuning after the earthquake with emphasis on the beam loss mitigation efforts.  
TUPB082 Beam Loss Track Measurements by a Fast Trigger Scheme in J-PARC Linac 663
  • H. Sako, T. Maruta, A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
  Funding: Work partially supported by Grant-in-Aid for Challenging Exploratory Research
In J-PARC Linac, highest beam loss has been observed at the ACS (Annular-Coupled Structure linac) section. The primary source of the beam loss is considered to be H0 produced by an interaction of H beams with remnant gas. The H0 hits the beam duct, converted to H+, and escapes from the beam duct. To detect the H+'s and estimate the absolute magnitude of the beam loss, we constructed a detector system, which consists of 6 planes of hodoscopes made of 16 scintillation fibers with 64 x 64 mm2 area. The scintillation light is measured by multi-anode photomultipliers. In the ACS section, two planes to measure horizontal positions are installed, and at about 1 m downstream positions, two planes for horizontal measurements and two for vertical measurements are placed. We will reconstruct charged particles passing through all the 6 planes, and measure the velocity by time-of-flight and energy loss to identify particle species. We present new measurements since the recovery of the J-PARC after the earthquake started in April 2012 by a new fast trigger scheme using dynode signals of photomultipliers in order to improve signal-to-noise ratios.
TUPB101 Beam Loss Occurred at DTL Cavity in J-PARC Linac 696
  • A. Miura, K. Hirano, T. Ito, T. Maruta
    JAEA/J-PARC, Tokai-mura, Japan
  • M. Ikegami
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • T. Miyao, F. Naito, K. Nanmo
    KEK, Ibaraki, Japan
  The beam operation of J-PARC linac was suspended until December 2011 due to the damage by the Tohoku earthquake in March 2011. After resumed the operations, we measured the residual radiation along with the beam line during a short interval. Because the higher residual radiation was detected at the surface of drift tube linac (DTL) cavity by radiation survey, we installed the scintillation beam loss monitors (BLM) at the points where the higher radiation was detected to understand the cause of the radiation. Even the DTL section is low energy part of the linac, fine structure of the beam loss was observed by the scintillation BLM. And we measured the beam loss occurred at the DTL with the parameters of beam orbit and cavity settings. Also, the BLM is employed for the linac tuning. In this paper, the result of the radiation measurement and beam loss signals obtained by the scintillation BLMs are presented.  
TUPB102 Design and Performances of Phase Monitor in J-PARC Linac 699
  • A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
  • Z. Igarashi, T. Miyao
    KEK, Ibaraki, Japan
  J-PARC linac employs a fast current transformer (FCT) as a beam phase monitor to calculate the beam energy by time-of-flight method. We have installed and used 61 FCTs in the current beam line. Because the phase measurements at additional 41 points in the future ACS sections are required for the energy upgrade project with adding 21 ACS (Annular Coupled Structure) cavities, we stared the design and fabrication of FCTs as the phase measurement devices. In addition, J-PARC linac employs the 4-stripline beam position monitors (BPMs) for the beam position measurement. It has been considered that the signals from striplines of BPM would be useful for a phase measurement. A phase measurement using a BPM has been successfully conducted. In order to evaluate the performances of the FCT, the signal sensitivity and cut-off frequency of newly fabricated FCT are measured. Also, these data of the BPM are also measured to be compared with the data of FCT. Based on the results of the comparing both measurements, the superiority of both monitors for beam phase measurement is discussed.