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Hotchi, Hideaki; J-PARC Beam Commissioning Team
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.6 - 10, 2011/09
The J-PARC is a multi-purpose proton accelerator facility amiming at MW-class output beam power, consisting of a 400 MeV H
linac, a 3-GeV RCS, a 50-GeV MR (Main Ring) and three experimental facilities, the MLF (materials and life science experimental facility), the HD (hadron experimental hall) and the NU (neutrino beam line). The J-PARC beam commissioning started in November 2006 from the linac to the downstream facilities. The current output beam power from the RCS to the MLF users is 210 kW, and the MR delivers 145 kW beam to the NU by fast extraction and a few kW beam to the HD by slow extraction. In this talk, we present a current status of the J-PARC beam commissioning, in which a recent progress in the course of the RCS beam power ramp-up scenario will be described in more detail. This talk will focus on the issues (including beam dynamics), challenges, solutions, and lessons learned during the commissioning and user operation of J-PARC and future plans.
Yamamoto, Kazami; Yamazaki, Yoshio; Yoshimoto, Masahiro; Kamiya, Junichiro; Harada, Hiroyuki; Saha, P. K.; Hotchi, Hideaki; Kinsho, Michikazu; Kato, Shinichi*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1605 - 1607, 2011/09
In the J-PARC RCS, the significant losses were observed at the branch of H0 dump line and the Beam Position Monitor which was put at the downstream of the H0 dump branch duct. From the beam study, we were certain that these losses were caused by the scattering of the injection and circulating beam at the charge exchange injection foil. In order to mitigate these losses, we started to develop a new collimation system in the H0 branch duct. We present latest study results and overview of this new collimation system.
Sako, Hiroyuki; Maruta, Tomofumi; Miura, Akihiko
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1251 - 1253, 2011/09
Highest beam loss has been observed at the ACS section in the J-PARC linac. The source of the loss is considered to be H
produced as Hs ionized with remnant gas. The H hits the beam duct and is converted to H
and escapes from the beam duct. We constructed scintillating fiber hodoscopes to detect these H's. They consist of 4 planes with 16 scintillating fibers of 64 mm-long and a 4 mm 
4 mm cross section. We present measurements results of beam loss particles with the hodoscopes installed at ACS.
Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Tamura, Fumihiko; Yamamoto, Masanobu; Sato, Tomonori; Yamamoto, Masahiro; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.107 - 109, 2011/09
J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and 50 GeV Synchrotron (MR) employ the Magnetic Alloy (MA) loaded RF cavities. We observed the impedance reductions of MR RF cavities. Opening the RF cavities, we found that the impedance reductions were caused by the corrosion on the core cutting surfaces. The copper ions in the cooling water from hollow conductors of main magnets might accelerate the corrosion process.
Maruta, Tomofumi
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2595 - 2597, 2011/09
Suppression of a beam loss is the key issue to operate an accelerator stably for a long term, because the beam loss makes accelerator components radioactivated and a high radioactivation becomes an obstacle for maintenance works by hand. One of the major origins of the beam loss at the J-PARC linac is the scattering process of beam particles (H for J-PARC Linac) with residual gas inside the beam duct. For the study on the beam loss coming from the H scattering process, I developed a library that can handle H and H by Geant4 toolkit. I will introduce some parameters, especially for cross sections of H and H, in the library and show some simulation results with the library.
Maruta, Tomofumi; Miura, Akihiko; Sako, Hiroyuki; Wei, G.; Ikegami, Masanori*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1245 - 1247, 2011/09
In J-PARC linac, we have been experiencing beam losses at the beam transport line after the linac exit. There has been an argument that the longitudinal loss could be a cause of the beam loss, which motivated us to conduct an experimental investigation on the margin between the longitudinal acceptance of the linac and the actual beam distribution. In the experiment, we have introduced a "tank level scan" to measure the margin in the energy direction in addition to the conventional phase scan which has been employed to measure the margin for the phase direction. The measurement scheme and experimental results are presented in this paper.
Maruta, Tomofumi; Miura, Akihiko; Sako, Hiroyuki; Wei, G.; Ikegami, Masanori*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2592 - 2594, 2011/09
Since we have no tool to measure the longitudinal beam profile at the J-PARC linac, we have tuned operational parameters for the matching of both longitudinal and transverse directions only from the measurement of the transverse beam profile by wire scanners at matching sections. Therefore it is very useful for us if the beam profile on the longitudinal phase space can be measured. It motivated us to measure the longitudinal acceptance of the DTL. In the measurement, we introduced a "tank level scan" to measure the shrinkage of the acceptance when we reduce the tank level of 1st DTL cavity in addition to the conventional phase scan. In this presentation, we will present the measurement scheme and experimental results.
Tamura, Fumihiko; Yamamoto, Masanobu; Omori, Chihiro*; Schnase, A.; Yoshii, Masahito*; Nomura, Masahiro; Toda, Makoto*; Shimada, Taihei; Hara, Keigo*; Hasegawa, Katsushi*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2733 - 2735, 2011/09
The beam loading compensation is a key part for acceleration of high intensity proton beams in the J-PARC RCS. In the wide-band MA-loaded RF cavity, the wake voltage consists of not only the accelerating harmonic component but also the higher harmonics. The higher harmonic components cause the RF bucket distortion. We employ the RF feedforward method to compensate the multi-harmonic beam loading. The full-digital feedforward system is developed, which compensates the first three harmonic components of the beam loading. We present the results of the beam test with a high intensity proton beam (
ppp). The impedance seen by the beam is greatly reduced, the impedance of the fundamental accelerating harmonic is reduced to less than 25 
in a full accelerating cycle, while the shunt resistance of the cavity is in the order of 800 . The performance of the feedforward system is promising for achievement of the design beam power, 1 MW, in the future.
Hayashi, Naoki; Hotchi, Hideaki; Kamiya, Junichiro; Saha, P. K.; Takayanagi, Tomohiro; Yamamoto, Kazami; Yamamoto, Masanobu; Yamazaki, Yoshio
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2730 - 2732, 2011/09
The J-PARC RCS is a high beam power Rapid-Cycling Synchrotron (RCS). The original designed injection energy is 400 MeV, although presently it is 181 MeV, and its beam power is limited to 0.6 MW. Works to recover the Linac energy are ongoing and injection magnets power supplies upgrade for two bump and new knob are required in the RCS. In order to achieve 1 MW designed beam power, new instrumentation, like quadrupole corrector or to reduce kicker impedance, are also planned simultaneously. Activities related injection energy recovery in the J-PARC RCS are presented.
Miura, Akihiko; Hasegawa, Kazuo; Oguri, Hidetomo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2328 - 2330, 2011/09
On March 11, 2011, the great earthquake occurred off the Pacific coast of Tohoku. This earthquake and related ones caused the big damage of the J-PARC accelerators. As for the beam monitors in J-PARC linac, some commissioning tools had damage and the vacuum leakage was observed. In the recovery work, we inspected the damage and put the emergency steps for the vacuum equipment. In this paper, detailed inspection results of beam monitors are described and also the recovery work is introduced.
Miura, Akihiko; Maruta, Tomofumi; Sako, Hiroyuki; Hasegawa, Kazuo; Ouchi, Nobuo; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1257 - 1259, 2011/09
Ar-CO
gas proportional beam loss monitors (BLMs) have measured the beam loss through operations, but they are also sensitive to background noise of X-ray emitted from RF cavities. For the future energy upgrade of J-PARC linac, because 21 RF cavities are additionally installed in the beam line, the background noise would be serious problem. We employed the scintillation monitors to measure the beam loss which would bring more accurate beam loss measurements with suppression of X-ray noise. As the measurement results, a good signal to noise ratio is observed for the scintillation monitor with quite low sensitivity to the background X-ray. In addition, the availability of the scintillation monitor is also confirmed at the low energy part. This paper describes the beam loss measurement system using a scintillation monitor.
Morishita, Takatoshi; Asano, Hiroyuki; Ikegami, Masanori*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2601 - 2603, 2011/09
The alignment has seriously been damaged due to the large earthquake on March 11th, 2011 in eastern Japan. There has been observed more than 40 mm settlement and about 25 mm horizontal deformation at the straight section in the linac accelerator tunnel. After that earthquake, there was continuous settlement in the straight section for two months. The linac accelerator tunnel has two expansion joints at the transport section to RCS. At these joints, abrupt displacements have been observed more than several millimeters both horizontally and vertically. Now, realignment started for restoration of the linac alignment.
Takahashi, Hiroki; Kojima, Toshiyuki; Tsutsumi, Kazuyoshi; Narita, Takahiro; Nishiyama, Koichi; Sakaki, Hironao; Maebara, Sunao
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1734 - 1736, 2011/09
Control system for the IFMIF/EVEDA prototype accelerator consists of six subsystems; Central Control System (CCS), Local Area Network (LAN), Personnel Protection System (PPS), Machine Protection System (MPS), Timing System (TS) and Local Control System (LCS). The Prototype Accelerator provides the deuteron beam with the beam power more than 1 MW, and this control system is required the high reliability and usability to perform various operation modes for beam commissioning. To satisfy these requirements, we are developing mainly PPS, MPS and TS at the beginning. This paper presents the status of hardware development of the PPS, MPS and TS.
Maebara, Sunao
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.101 - 103, 2011/09
In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a coupled cavity type of RFQ, which has a longitudinal length of 9.78 m, was proposed to accelerate deuteron beam up to 5 MeV. The operation frequency of 175 MHz was selected to accelerate a large current of 125 mA in CW mode. The driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As the RF input coupler design, RF losses including a loop antenna and an RF vacuum window, based on a 6 1/8 inch co-axial waveguide were calculated. In this conference, these results and thermal analysis results in CW operation mode will be presented in details.
Takayanagi, Tomohiro; Hayashi, Naoki; Togashi, Tomohito; Ueno, Tomoaki; Watanabe, Yasuhiro; Kinsho, Michikazu
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.3403 - 3405, 2011/09
In the bump system of the J-PARC (Japan Proton Accelerator Research Complex) 3-GeV RCS (Rapid Cycling Synchrotron), the performance improvement according to upgrade of the LINAC (Linear Accelerator) to 400 MeV beam is planned. Both the increase of the power supply capacity and the improvement of the setting accuracy of the output current are required. Moreover, the operating point that the vibration of the current ripple resonates with betatron tune was clarified. Therefore, the present level of the current ripple is necessary to decrease to half or less. The development of the pulse power supply system that solves the problems of the current ripple is required. The contents both the improvement plane of the bump system performance and the upgrade system of the power supply are explained.
Shobuda, Yoshihiro; Tamura, Fumihiko; Yamamoto, Masanobu; Chin, Y. H.*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.595 - 597, 2011/09
Saha, P. K.; Yoshimoto, Masahiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamazaki, Yoshio; Kinsho, Michikazu; Irie, Yoshiro*; Sugai, Isao*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.3511 - 3513, 2011/09
Yoshimoto, Masahiro; Hayashi, Naoki; Yamamoto, Kazami; Hotchi, Hideaki; Saha, P. K.; Harada, Hiroyuki; Kinsho, Michikazu
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.2412 - 2414, 2011/09
In the Japan Particle Accelerator Complex (J-PARC) 3 GeV Rapid Cycling Synchrotron (RCS), we found that CD leakage fields from the extraction beam line significantly affected the beam. For this issue, we installed additional shields and got the 40% reduction of the DC leakage field. Thus the circulating beam loss was successfully reduced.
Yoshimoto, Masahiro; Yamamoto, Kazami; Yamazaki, Yoshio; Kinsho, Michikazu; Kato, Shinichi*
Proceedings of 2nd International Particle Accelerator Conference (IPAC 2011) (Internet), p.1545 - 1547, 2011/09
For the new collimation system at the H0 dump line junction in the J-PARC RCS, we redesigned a new H0 dump branch duct. This new branch duct is made of the two kinds of the stainless steels as follows; SUS316L austenitic stainless steel and SUS430 ferritic stainless steel. In order to verify the material selection, several material testing of SUS430 were carried out with test ducts, and the magnetic annealing condition for SUS430 was fixed.
