Author: Miura, A.
Paper Title Page
MOPME024 Status of Beam Loss Spatial Distribution Measurements at J-PARC Linac 524
 
  • H. Sako, T. Maruta, A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
 
  Funding: This work was supported by JSPS KAKENHI Grant Number 24510134.
We have developed 8-plane (4 horizontal and 4 vertical) scintillating fiber hodoscope system to measure proton tracks due to beam loss in the ACS section at the J-PARC linac. The detector consists of upstream 4 planes (two horizontal and two vertical) and downstream 4 planes (two horizontal and 4 vertical). The time of flight measuremments between the upstream and downstream subsystems allow proton identification and energy mesurements. In summer of 2012, we have installed remote position movement system, which enables measurements of spatial distributions of proton tracks. In this presentation we show status of mesurements and data analysis.
 
 
MOPME026 Beam Monitor Layout for Future ACS Section in J-PARC Linac 529
 
  • A. Miura, M. Ikegami, H. Oguri
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
 
  In J-PARC Linac, an energy and intensity upgrade project has started since 2009 using Annular Coupled Structure (ACS) cavities. With this upgrade, the design peak current will be increased from the present 30 mA to 50 mA, and the energy from 181 MeV to 400 MeV. Along with these significant upgrades of the beam parameters, beam monitors should be followed. Also, the bunch shape monitor and new beam loss monitoring system will be employed for the new beam line. Newly fabricated devices will be delivered in the ACS beam line. And beam monitor layout of the upstream and downstream of ACS beam line will be modified. In this paper, we introduce the development of the beam diagnostic devices for the project and the new designed beam monitor layout.  
 
MOPME027 Bunch Length Measurement of 181 MeV Beam in J-PARC Linac 532
 
  • A. Miura, H. Oguri, N. Ouchi, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
  • A. Feschenko, A.N. Mirzojan
    RAS/INR, Moscow, Russia
  • K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
  • M. Ikegami
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • T. Maruta
    KEK/JAEA, Ibaraki-Ken, Japan
 
  In J-PARC Linac, an energy and intensity upgrade project has started since 2009 using Annular Coupled Structure (ACS) cavities. Because the longitudinal matching before ACS cavities is additionally required, we decided to employ the bunch shape monitors (BSMs) to measure the longitudinal beam profile. After three years from the start of BSM project, three BSMs were fabricated. All three BSMs were installed during the summer shutdown of 2012. We tried to measure the longitudinal beam profile exited from SDTL cavities. In this paper, we introduce the outline of BSM project, the first data acquisition and related small problems.  
 
WEPFI016 Upgrade of Power Supply System for RF-Chopper At J-PARC Linac 2735
 
  • K. Futatsukawa, Z. Fang, Y. Fukui, M. Ikegami, T. Miyao
    KEK, Ibaraki, Japan
  • E. Chishiro, K. Hirano, Y. Ito, N. Kikuzawa, A. Miura, F. Sato, S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
  • T. Hori
    JAEA, Ibaraki-ken, Japan
  • Y. Liu, T. Maruta
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Suzuki
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
 
  In the J-PARC Linac, the radio frequency deflector was adopted as a chopper to capture the particles into the RF-bucket in the next synchrotron. The chopper, consists of two deflectors, was installed on the medium-energy beam-transport line. In the operation of the RF-chopper, the fast rise/fall time of the pulse is a fundamental requirement to minimize the beam loss due to insufficient deflection to some beam bunches. In the previous system, the two series-connected chopper deflectors were driven by one solid- state amplifier. However, the fall time indicated a poor result to effect the ringing into each cavity. Therefore, the additional solid-state amplifier and low level RF system were installed in the summer 2012 and the connection changed to the parallel system from the series using two amplifiers. The rise/fall time of the chopped beam, is defined as the step height of 10% and 90%, was about 20 nsec in the beam current of 15 mA and the effect of the ringing was decreased. We would like to introduce the performance of the new chopper system.  
 
THPWO028 Commissioning Plan for Energy Upgrade of J-PARC Linac 3821
 
  • M. Ikegami, Z. Fang, K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Maruta
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • A. Miura, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  In J-PARC linac, we plan to have an energy and intensity upgrade in summer 2013. The upgrade involves replacement of the ion source and RFQ (Radio Frequency Quadrupole linac), and addition of ACS (Annular Coupled Structure linac) cavities after existing SDTL (Separate Drift Tube Linac) section. With this upgrade, the design peak current will be increased from the present 30 mA to 50 mA, and the energy from 181 MeV to 400 MeV. This significant upgrade will be followed by a full-scale beam commissioning campaign. In this paper, we present the plan for the commissioning with outlining the assumed commissioning schemes.  
 
THPWO029 Beam Loss Monitoring and Mitigation at J-PARC DTL 3824
 
  • T. Maruta
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • K. Futatsukawa, M. Ikegami, T. Miyao
    KEK, Ibaraki, Japan
  • T. Ito, A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
 
  Close radiation survey at the cavity outer surface has indicated a significant beam loss in the first tank of J-PARC DTL (Drift Tube Linac) which has been localized at a certain drift tube. It has motivated us to measure the beam loss at the DTL, and we have installed beam loss monitors of scintillator type at the cavity surface. It is challenging to monitor the beam loss due to low energy of lost particles and shielding by the thick cavity wall. In this paper, we report the results of beam loss measurement and beam loss mitigation tuning using the beam loss monitors.  
 
THPWO030 Recent Progress in Beam Commissioning of J-PARC Linac 3827
 
  • M. Ikegami, Z. Fang, K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
  • Y. Liu
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Maruta
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • A. Miura, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  The beam operation of J-PARC linac has been restored from the earthquake, and started to pursue higher beam power operation. We have also started to prepare for coming energy and intensity upgrade. In this paper, we review recent progress in beam commissioning of J-PARC linac with emphasis on the beam loss mitigation and preparation for the upgrade.  
 
THPWO035 Numerical Study on the Effect of Magnetic Shield of a Bunch Shape Monitor in J-PARC Linac 3842
 
  • J. Tamura, H. Ao, A. Miura, N. Ouchi
    JAEA/J-PARC, Tokai-mura, Japan
  • M. Ikegami
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • T. Maruta
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Miyao, K. Takata
    KEK, Tokai, Ibaraki, Japan
 
  In the annual shutdown period of 2012, three bunch shape monitors (BSMs) have been installed to the J-PARC linac beam transport line at the downstream of the 181-MeV separated DTL. To measure the longitudinal micro-bunch shape, the BSM detects the electrons produced by the accelerated protons hitting the negatively energized wire. Due to the space limitation, the each BSM is installed at the center of the quadrupole doublet, where the fringe field from the quadrupole magnets exists. It has been observed that the fringe field significantly affects the orbit of the emitted electrons. To shield the magnetic field, iron plates have been inserted to the spaces between the quadrupole magnets and BSM. This causes changes of the total magnetic flux density (GL) and the amount of quadrupole component of the fringe field. In this paper, numerical estimation of the shield effect is presented.