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Harada, Hiroyuki; Saha, P. K.; Yamane, Isao*; Kato, Shinichi; Kinsho, Michikazu; Irie, Yoshiro*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.983 - 986, 2016/11
The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate.
Tamura, Fumihiko; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.808 - 810, 2016/11
J-PARC MR provides high intensity proton beams of 390 kW to the neutrino experiment. The proton beams are extracted by fast extraction. It has been found that the cavity voltage goes up for about 20 
s just after extraction. It is because the rf feed forward system for beam loading compensation outputs compensation signals for its system delay. The MR cavity has a relatively low Q value of 22 and the cavity voltage can varies in the order of 10 s. The voltage variation of the cavity voltage increases with the beam intensity and it is a possible reason of the damage of the gap capacitors. A counter measure using the inhibit function of the summation amplifier in the LLRF system has been applied. In this presentation, we present the details of the cavity voltage variation and the results of the counter measure. Also, we present the analysis of beam loading using the voltage variation.
Ikeda, Hiroshi; Kikuzawa, Nobuhiro; Yoshii, Akinobu*; Kato, Yuko
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.637 - 640, 2016/11
no abstracts in English
Kurihara, Toshikazu*; Kobayashi, Hitoshi*; Sugimura, Takashi*; Hirano, Koichiro
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.814 - 816, 2016/11
A problem of irradiation damage is the one observed in each part of a component of particle accelerators; accelerating tubs, scrapers, monitors and neutron targets. In-situ observation by an actual proton accelerator is made our last target. We observed the radiation damage of the various materials used by particle accelerators. From the distant place the target which is in the high radiation area, we propose the method to get information from the catoptric light from the target using a laser as a light source. A principle of this observation method as well as generating process of blisterings and limitation of this method will be reported.
Suganuma, Kazuaki; Hiroki, Fumio; Ito, Takashi; Yamazaki, Yoshio
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.304 - 306, 2016/11
J-PARC LINAC has a problem that the amount of the flowing water is reduced. It spends such time from alarm to the restoration that it is desirable to take measures. So we have to solve this problem. We tried to focus again on the related water level fluctuation in the storage tank of cooling water equipment and the flow rate fluctuation all of the cooling water that has observed in cooling water equipment named RI4 from RFQ to SDTL of the LINAC. At the same time, we check new information of the operating data. We have hypothesized about the cause of fluctuation of the whole flow rate. That can be deterioration of water quality and lacking of performance of circulation pumps. That can be deterioration of water quality and lacking of performance of circulation pumps.
Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.61 - 65, 2016/11
After the RF power supply upgrade, the J-PARC 3-GeV RCS restarted a 1-MW beam test in October 2015. In the beam test in October, we successfully removed longitudinal beam loss by beam loading compensation as well as minimized space-charge induced beam loss by injection painting. In addition, in this beam test, beam instability was also well suppressed by controlling the tune and the chromaticity. Furthermore, in the following beam test, the transverse painting area was successfully expanded by introducing both quadrupole correctors and anti-correlated painting scheme, by which a foil scattering part of beam loss during charge-exchange injection was further reduced. By these recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents recent progresses of 1-MW beam tuning with particular emphasis on our approaches to beam loss issues.
Yoshimoto, Masahiro; Takeda, Osamu; Harada, Hiroyuki; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1097 - 1101, 2016/11
In the 3 GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC), a beam collimation system which aims to localize the beam loss at the collimators and to reduce the level of residual doses at the other devices is installed in the ring to achieve a 1MW high power beam operation. However vacuum leakage due to the collimator trouble occurred in April, 2016. Therefore an absorber No.5 in the collimation system had to be removed from the ring. Before resuming the beam operation, a new beam loss situation was simulated by using the particle tracking code. In the beam tuning, the transition of the beam loss distribution was measured by the beam loss monitors. We verified that the new beam situation was permissible, and the beam operation can be resumed. By following-up the transition of the residual dose distribution along the ring, the detailed beam loss structure can be understood. In this presentation, we report an influence of ring-collimator malfunction on beam loss localization in the J-PARC RCS.
Horino, Koki; Takayanagi, Tomohiro; Ueno, Tomoaki; Tobita, Norimitsu*; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.703 - 707, 2016/11
A user operation with 400 MeV injection beam energy from the LINAC (Linear Accelerator) was started in February 2014. However, in 2015 one year later, the coil support bolt of the horizontal shift bump magnet was felled and the water leakage of the cooling copper pipe of the connection conductor bar was occurred. After the permanent measures, a stable operation has been continued without trouble. This paper reports the contents of the trouble and the permanent measures of the magnet.
Ueno, Tomoaki; Takayanagi, Tomohiro; Horino, Koki; Tobita, Norimitsu*; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.720 - 724, 2016/11
The horizontal and vertical paint bump magnets of the J-PARC (Japan Proton Accelerator Research Complex) 3-GeV RCS (Rapid Cycling Synchrotron) realize the uniform beam distribution of the RCS circulating beam by a small injection beam of the emittance form the Linac (Linear Accelerator). The power supply of the horizontal painting magnet has been performed a good accuracy less than 
1% deviation to programmed pattern. However, the fluctuation of the output current less than 1% is equivalent to 1 mm displacement of the beam orbit and it increases the beam loss. This paper reports the present status and the result of the fluctuation measures of the painting bump power supply system.
Takayanagi, Tomohiro; Ueno, Tomoaki; Horino, Koki; Togashi, Tomohito; Tobita, Norimitsu*; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.699 - 702, 2016/11
no abstracts in English
Tani, Norio; Watanabe, Yasuhiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Kinsho, Michikazu; Igarashi, Susumu*; Sato, Yoichi*; Shirakata, Masashi*; Koseki, Tadashi*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.708 - 711, 2016/11
At the J-PARC Main Ring (MR), there have been various investigation carried out at the moment aiming at the beam operation of MW order. As one of the investigations, a study of the Rapid-Cycling Synchrotron (RCS) magnets was implemented. Increase of the extraction energy of RCS was needed to reduce beam loss, as beam loss in the MR injection region was large under influence of Space Charge effect at the injection beam of 3GeV. Therefore conceptual design of the extraction energy upgrade using dipole and quadrupole magnets of RCS was performed. In this paper, we will report the contents of the study in extraction energy upgrade of RCS magnets and problems which became clear as a result.
Takei, Hayanori; Hirano, Koichiro; Tsutsumi, Kazuyoshi; Chishiro, Etsuji; Miura, Akihiko; Kondo, Yasuhiro; Morishita, Takatoshi; Oguri, Hidetomo; Meigo, Shinichiro
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.987 - 991, 2016/11
Accelerator-driven system (ADS) is one of candidates to transmute long-lived nuclides such as minor actinide (MA) produced at nuclear reactor. For efficient transmutation of the MA, precise prediction of neutronics of ADS is indispensable. In order to obtain the neutronics data for the ADS, J-PARC has a plan to build the Transmutation Physics Experimental Facility (TEF-P). Since the TEF-P requires stable power of the beam and will operate with thermal power less than 500 W and the proton beam power of 10 W so that a stable and meticulous beam extraction method is required to extract small amount of the beam from the high power LINAC beam with 250 kW. To fulfill requirement, Laser charge exchange method (LCE) has been developed for delivery of 400-MeV proton beam with 25Hz to the TEF-P. The LCE strips the electron of H
beam and H
will separate at the bending magnet at the proton beam transport. The LCE device consists of YAG-laser with high power as 1.6 J/shot and 25 Hz and transport control system with high accuracy of the beam position. For the demonstration of the charge exchange of the H, the further LCE tests is conducted using H beam with energy of 3-MeV at RFQ test stand in J-PARC. In this paper, present status of LCE tests is presented.
Chishiro, Etsuji; Sagawa, Ryu*; Toriyama, Minoru*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.400 - 402, 2016/11
Klystron power supplies in the J-PARC have been generated high voltage DC power by chopping 12-phase AC voltage power by thyristors, and boosting the voltage up to 110 kV in step-up transformer and rectifying the voltage in high voltage rectifiers. Some of the high voltage transformers (HVTR), which consist of the step-up transformer and the high voltage rectifier and the reactor, were often broken in the running time of over 30,000 hours. This failure caused the long-term shut down of the J-PARC facility. The high voltage rectifier composed diodes and condensers by a series connection of 66 stages. Investigation of the failed rectifier shows that the capacitors ware applied the overvoltage because the flashover occurred on the ceramic surface. We investigated the mechanisms applying the overvoltage and took measure for the overvoltage to the rectifier. The HVTR with the improved rectifier has been operating for long term to assess the modification effect.
Togashi, Tomohito; Takayanagi, Tomohiro; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.725 - 728, 2016/11
The 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC (Japan Proton Accelerator Research Complex) has the pulse kicker power supply system which use the thyratron switches for beam extraction. It has passed from operation starting for more than 10 years, but an exchange of a part and check are being put into effect periodically, so a kicker power supply also keeps operation smoothly now. I spent long time and studied how to use, so thyratron could be used now for more than 10,000 hours. But long years have passed, so selection of a substitute of a discontinuance part is a pending problem. Silicon oil has also degraded, so I have to consider a way of a performance recovery and a procedure of an exchange. This report explains the current state of the kicker magnet power supply from a result of the regular inspection and conditions.
Kato, Shinichi; Harada, Hiroyuki; Hatakeyama, Shuichiro; Kawase, Masato; Yamamoto, Kazami; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1089 - 1093, 2016/11
In the J-PARC RCS, the residual gas ionization profile monitor (IPM) is adopted for the nondestructive detection of the 1D transverse distribution of the circulating proton beam. The IPM mainly consists of the divided electrodes generating the external electric field and the detection unit. For the profile measurement, the residual gas ionized by the beam is transported to the detection unit by the external transverse electric field and amplified by the Multi-Channel Plate (MCP) as the electron. After that, these electrons are detected and the 1D distribution is reconstructed. To improve IPM performance, some updates have been performed continuously such as the optimization of the electric field potential and the introduction of the new MCP which has the gradual gain response to the applied voltage. As a result, the IPM shows intended performance in the beam commissioning with the low current condition. However, the distribution cannot be measured in the high current condition such as over 100 kW because the noise increases and hides the signal. To solve this problem, we investigated the source of this noise and examined measures. To compare the simulation and the noise measurement results, we identified the cause of the noise as the electric field from the beam. Therefore, we developed additional electrode component to shield that field based on the simulation result. This component will be installed in 2016 summer. It is expected that the noise is reduced to be 1/100 compared with present one by the new component and the distribution measurement can be performed in the high current condition.
Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Ueno, Akira; Shibata, Takanori*; Nammo, Kesao*; Shinto, Katsuhiro; Oguri, Hidetomo
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.940 - 943, 2016/11
In 2014 October, operation of cesium-seeded Radio Frequency (RF)-driven negative hydrogen ion (H) source was started in J-PARC LINAC. Due to the skillful RF antenna screening and the proper pre-conditioning process, long term unscheduled beam stop due to the antenna failure did not occur for more than 1 year. The continuous operation of 1,350 hours with a peak beam current of 45 mA was achieved in the recent beam run. Moreover, the fluctuation of beam current in a low energy beam transport (LEBT) is kept within 2% of target value by application of three feedback systems. An ion source test-stand was assembled to investigate the ion source beam characteristic, for example, the emittance at the position of the RFQ entrance. In the presentation, we will report the recent status of the ion source operation and some experimental results obtained at the ion source test-stand.
Kamiya, Junichiro; Yanagibashi, Toru; Ogiwara, Norio; Kinsho, Michikazu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1193 - 1196, 2016/11
In this study, we propose a new in situ degassing method by which only kicker magnets in the accelerator beam line are baked out without raising the temperature of the vacuum chamber to prevent unwanted thermal expansion of the chamber. By simply installing the heater and thermal radiation shield plates between the kicker magnet and the chamber wall, most of the heat flux from the heater directs towards the kicker magnet. The result of the verification test showed that each part of the kicker magnet was heated to above the target temperature with a small rise in the vacuum chamber temperature. The outgassing rage was reduced to one tenth comparing to the case without bake out.
Yamamoto, Kazami; Okabe, Kota; Kamiya, Junichiro; Yoshimoto, Masahiro; Takeda, Osamu; Takayanagi, Tomohiro; Yamamoto, Masanobu
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.314 - 318, 2016/11
The 3 GeV Rapid-Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) project generates 1MW proton beam for the neutron experiments and Main ring accelerator. In case of such high intensity hadron accelerator, the most important issue is to reduce the uncontrolled loss. The beam collimation system is designed for this purpose. In the present design, the physical aperture is 1.5 times wider than the primary collimator aperture and the beam loss can be enough localized on this condition. After a startup of RCS in 2007, the collimator system of RCS worked well. But vacuum leakage occurred during the maintenance period in April, 2016. Since it was expected that the beam collimator was radio-activated very much, we took the influence of radiation into consideration and designed the collimator (ie. a remote clamp system to connect/take off it with a vacuum flange away from itself). Therefore, during the recovery work of the collimator, we were able to reduce the worker dose to less than 60 micro Sv though the collimator block had a residual dose of 40 mSv/h.
Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Naito, Fujio*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1409 - 1412, 2016/11
After the summer maintenance in 2015, user operation for the hadron experimental facility (HD) and the life science experimental facility (MLF) was resumed in the middle of October after the tuning of accelerator at J-PARC. In December, we reduced the repetition cycle from 6.0 seconds to the 5.52 seconds at the main ring (MR) and therefore, we have improved beam power to 42 kW, while it was 24 kW in April. The peak beam current at the linac by December 2015 was 30 mA, but we have increased to 40 mA in January, and the tuning was followed by the 3 GeV synchrotron (RCS) and the MR for user operation condition. As a result we improved a beam power to the neutrino experimental facility (NU) to 390 kW by the tuning while it was ranged 300 to 330 kW at 30 mA. User program was performed at 500 kW at the MLF, but it was suspended by a defect of a target in November. It was replaced for a spare one and resumed at 200 kW in February. We have several faults to stop beam operations: ventilation system at the linac by a short circuit, a vacuum leak at the RCS collimator, a breakdown of bending magnet of the MR, etc.
Matsuda, Makoto; Osa, Akihiko; Ishizaki, Nobuhiro; Tayama, Hidekazu; Nakanoya, Takamitsu; Kabumoto, Hiroshi; Nakamura, Masahiko; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1413 - 1417, 2016/11
The tandem accelerator was operated over a total of 140 days and delivered 22 different ions to the experiments in the fields of nuclear physics, nuclear chemistry, atomic physics, solid state physics and radiation effects in material. Maximum accelerating voltage is keeping up 18 MV and there was used for ten days on this voltage. However, electric discharge was occurred frequently in December and accelerating voltage fell to 12 MV. The damaged acceleration tubes were replaced with the spare tube at the regular maintenance period in March. The superconducting booster was not operated. This paper describes the operational status of the accelerators and the major technical developments.
