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Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:0 Percentile:0.01(Optics)

Journal Articles

Dependence of charge-exchange efficiency on cooling water temperature of a beam transport line

Yamamoto, Kazami; Hatakeyama, Shuichiro; Saha, P. K.; Moriya, Katsuhiro; Okabe, Kota; Yoshimoto, Masahiro; Nakanoya, Takamitsu; Fujirai, Kosuke; Yamazaki, Yoshio; Suganuma, Kazuaki

EPJ Techniques and Instrumentation (Internet), 8(1), p.9_1 - 9_9, 2021/07

The 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex supplies a high-intensity proton beam for neutron experiments. Various parameters are monitored to achieve a stable operation, and it was found that the oscillations of the charge-exchange efficiency and cooling water temperature were synchronized. We evaluated the orbit fluctuations at the injection point using a beam current of the injection dump, which is proportional to the number of particles that miss the foil and fail in the charge exchange, and profile of the injection beam. The total width of the fluctuations was approximately 0.072 mm. This value is negligible from the user operation viewpoint as our existing beam position monitors cannot detect such a small signal deviation. This displacement corresponds to a 1.63$$times$$10$$^{-5}$$ variation in the dipole magnetic field. Conversely, the magnetic field variation in the L3BT dipole magnet, which was estimated by the temperature change directly, is 4.08$$times$$10$$^{-5}$$. This result suggested that the change in the cooling water temperature is one of the major causes of the efficiency fluctuation.

Journal Articles

Reliability of J-PARC accelerator system over the past decade

Yamamoto, Kazami; Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*

JPS Conference Proceedings (Internet), 33, p.011016_1 - 011016_7, 2021/03

The Japan Proton Accelerator Research Complex (J-PARC) is a multipurpose facility for scientific experiments. The accelerator complex consists of a 400-MeV Linac, a 3-GeV Rapid-Cycling Synchrotron (RCS) and a 30-GeV Main Ring synchrotron (MR). The RCS delivers a proton beam to the neutron target and MR, and the MR delivers the beams to the neutrino target and the Hadron Experimental Facility. The first operation of the neutron experiments began in December 2008. Following this, the user operation has been continued with some accidental suspensions. These suspensions include the recovery work due to the Great East Japan Earthquake in March 2011 and the radiation leak incident at the Hadron Experimental Facility. In this report, we summarize the major causes of suspension, and the statistics of the reliability of J-PARC accelerator system is analyzed. Owing to our efforts to achieve higher reliability, the Mean Time Between Failure (MTBF) has been improved.

Journal Articles

Analysis of J-HBC stripper foil for the J-PARC RCS

Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*

JPS Conference Proceedings (Internet), 33, p.011019_1 - 011019_7, 2021/03

The multi-turn charge-exchange H$$^{-}$$ beam injection scheme with stripper foils is one of the key techniques to achieve a MW-class high power proton beam. The J-PARC RCS adopts Hybrid type Boron-doped Carbon (HBC) stripper foil, which was developed in KEK to improve the lifetime. Indeed, the RCS user operation confirmed that HBC foil has the great advantage of a longer lifetime against high beam irradiation. To examine characteristics of the HBC foils, various beam studies were performed, such as the stripping efficiency measurement and long-term observation with an H$$^{-}$$ beam in the J-PARC RCS, foil analysis using RBS, EDR and PIXE methods, and SEM and TEM observation after the ion beam irradiation in Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) on National Institutes for Quantum and Radiological Science and Technology (QST). Recently, the deposition apparatus for the HBC foils from the KEK Tsukuba-site was relocated to the JAEA Tokai-site, and we started fabrication of new HBC foil in 2017. (The new one fabricated in JAEA we call J-HBC foil.) And, we continue investigations in TIARA with the J-HBC foils. Furthermore, in-depth researches by changing the process parameters of the foil deposition are carried on. Recent results suggest that the amount of the boron doped in the foil is more important parameter than the ratio of the discharge amount of carbon from cathode and anode electrodes. In this presentation, we will report the details of recent analysis of the J-HBC foil.

Journal Articles

Results of 1-MW operation in J-PARC 3 GeV rapid cycling synchrotron

Yamamoto, Kazami; Yamamoto, Masanobu; Yamazaki, Yoshio; Nomura, Masahiro; Suganuma, Kazuaki; Fujirai, Kosuke; Kamiya, Junichiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Yoshimoto, Masahiro; et al.

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.209 - 213, 2020/09

The J-PARC 3GeV Rapid Cycling Synchrotron (RCS) is aiming to provide the proton beam of very high power for neutron experiments and the main ring synchrotron. We have continued the beam commissioning and the output power from RCS have been increasing. In recent years, just before the summer shutdown period, we have been trying continuous supply of 1-MW high-intensity beam, which is the design value, to a neutron target. First trial was 1-hour continuous operation in July 2018, and second trial was 10-hours continuous in July 2019. In both cases, we achieved almost stable operation. Furthermore, in June 2020, we tried to operate continuously for over 40 hours. But in this case, some trouble occurred and the operation was frequently suspended. Through these continuous operation trials, we have identified issues for stable operation of 1 MW. In this presentation, we will report the results of 1-MW continuous operation and issues obtained from these results.

Journal Articles

First measurement and online monitoring of the stripper foil thinning and pinhole formation to achieve a longer foil lifetime in high-intensity accelerators

Saha, P. K.; Yoshimoto, Masahiro; Hatakeyama, Shuichiro; Hotchi, Hideaki; Harada, Hiroyuki; Tamura, Fumihiko; Yamamoto, Kazami; Yamazaki, Yoshio; Kinsho, Michikazu; Irie, Yoshiro*

Physical Review Accelerators and Beams (Internet), 23(8), p.082801_1 - 082801_13, 2020/08

 Times Cited Count:1 Percentile:35.83(Physics, Nuclear)

Journal Articles

Progress status in fabrication of HBC stripper foil for 3-GeV RCS at J-PARC in Tokai site

Yoshimoto, Masahiro; Yamazaki, Yoshio; Nakanoya, Takamitsu; Saha, P. K.; Kinsho, Michikazu

EPJ Web of Conferences, 229, p.01001_1 - 01001_7, 2020/02

In the 3-GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC), we adopted thick Hybrid type Boron-doped Carbon (HBC) stripper foil for the multi-turn H$$^{-}$$ charge-exchange injection. The HBC stripper foil developed at KEK has been successfully demonstrated to improve the foil lifetime significantly. Early manufacturing process of the stripper foil in the J-PARC had been carried out in following two steps: foil fabrication in KEK Tsukuba-site and foil preparation in JAEA Tokai-site. However, to proceed with the foil manufacturing in a same place efficiently, the carbon discharge arc-evaporation system for HBC stripper foil was removed from the Tsukuba-site and relocated in the Tokai-site. After reassembling of the carbon discharge arc-evaporation system, performance evaluation tests of new HBC foil which are produced at the JAEA Tokai site (J-HBC) are implemented at the TIARA facility of QST-Takasaki. As results of argon beam irradiation for lifetime evaluation, components analysis with RBS method, and impurity evaluation with micro-PIXE method, we can verify that the J-HBC foil performs pretty much equally to the original HBC foil. After the irradiation test by using 400MeV H$$^{-}$$ beam in the J-PARC RCS, user operation by using the J-HBC foil was successfully demonstrated for 10 days.

Journal Articles

Fabrication status of charge stripper foil for 3 GeV synchrotron of J-PARC

Nakanoya, Takamitsu; Yoshimoto, Masahiro; Yamazaki, Yoshio; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.545 - 549, 2019/07

In the 3 GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research complex (J-PARC), we adopted the carbon stripper foil for the multi-turn H- charge exchange injection. The charge exchange foil which use in RCS is fabricated by the arc discharge method with the boron doped carbon electrode. The foil fabricated this method is called HBC foil (Hybrid Boron mixed Carbon stripper foil). HBC foil had been developed at KEK. It has high durability for the beam irradiation damage. In past days, the foil fabrication process was conducted in KEK Tsukuba-site and the foil preparation process was conducted in JAEA Tokai-site. In 2017, the foil deposition apparatus has been relocated from KEK to JAEA, and we started both processes in Tokai-site. We carried out the offline beam irradiation test for the new HBC foil which fabricated in JAEA, and we confirmed that its performance is equivalent to the original HBC foil. Next we tested a new HBC foil with actual beam in RCS and we confirmed it could withstand 1 week beam irradiation. After that, we started user operation with the new HBC foil in 2018. So far we accomplished stable user operation for one year by using the new HBC foil only.

Journal Articles

Investigation for tiny metal contamination of water cooling system in J-PARC Linac

Suganuma, Kazuaki; Hiroki, Fumio; Ito, Takashi; Yamazaki, Yoshio

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.846 - 848, 2019/07

In the past, water flow decreased at water cooling system in J-PARC Linac. Contamination get mixed in cooling water. The problem was resolved by changing the system of the circulation pumps and reducing the tiny metal in water cooling system. However, suppression of occurring tiny metal is unresolved. The tiny metal is the unique problem of accelerator. It is caused by heavy using oxygen free copper and phosphorus deoxidized copper. The two copper is used for the part of accelerator and purified water. The object of the report is investigation of tiny metal contamination of water cooling system in J-PARC Linac.

Journal Articles

Production of the cooling towers fan bearing unit at J-PARC RCS

Fujirai, Kosuke; Suganuma, Kazuaki; Yamazaki, Yoshio

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1162 - 1164, 2019/07

Cooling water equipment of J-PARC RCS is supplying heat source equipment of an electromagnet cooling water. The cooling water is cooled in a cooling tower established outdoors. I heard abnormal noise from the bearing unit of the cooling tower fan in April, 2015 I decided to observe the state of the bearing unit. As a result of observation, it has a wound peculiar to a bearing of the pulley side. I decided to check why a bearing of the pulley side was damaged. When a fan goes around, a bearing on the pulley side is pulled by the upper and lower movement and fan belt which occur to a crosswise direction. I guessed a peculiar bruise the pulley side was that these vibration and load were added, and to have stuck. A bearing is the structure with which grease can't be replaced by the grease shutting tightly type, and I can think a small bruise has spread by the thing detached because a thing detached by braking drove in the remaining state in the bearing. So I decided to consider the above mentioned problem, move up and down for stable driving of a gas cooler fan and produce vibration of a crosswise direction and the bearing unit able to endure the load and replenish grease periodically newly. I'll report on vibration parameter of the structure of the bearing unit produced newly and an early stage by this publication.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Toyama, Takeshi*; Yamamoto, Noboru*; et al.

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1235 - 1239, 2019/07

After the summer shutdown in 2018, the J-PARC restarted user operation in late October. While beam power to the Materials and Life Science Experimental Facility (MLF) was 500 kW as before the summer shutdown, linac beam current was increased from 40 to 50 mA. Operation of the Main Ring (MR) was suspended due to the modification and/or maintenance of the Superkamiokande (neutrino detector) and Hadron experimental facility. The user operation was resumed in the middle of February for the Hadron experimental facility at 51 kW. But on March 18, one of the bending magnets in the beam transport line to the MR had a failure. It was temporary recovered and restored beam operation on April 5, but the failure occurred again on April 24 and the beam operation of the MR was suspended. In the fiscal year of 2018, the availabilities for the MLF, neutrino and hadron facilities are 94%, 86%, and 74%, respectively.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Yoshii, Masahito*; Yamamoto, Noboru*; Koseki, Tadashi*

Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1321, 2018/08

After the summer shutdown in 2017, the J-PARC restarted user operation in late October. The Materials and Life Science Experimental Facility (MLF) used a spare target and the beam power was limited to 150-200kW. The target was replaced with a new one in the summer shutdown. The beam power was for user operation gradually increased from 300 kW to 500 kW. We have successfully demonstrated 1MW 1hour operation in July 2018. The beam power for the neutrino experimental facility (NU) was 440 kW to 470 kW. The beam was delivered to the hadron experimental facility (HD) from January to February in 2018. The repetition rate of the main ring was shortened from 5.52 to 5.20 seconds, the beam power was increased from 44 to 50 kW. From March 2018, we delivered to the NU at 490 kW stably. In the fiscal year of 2017, the availabilities for the MLF, NU and HD are 93%, 89% and 66%, respectively.

Journal Articles

Present status of water cooling system at J-PARC linac 2018

Suganuma, Kazuaki; Hiroki, Fumio; Ito, Takashi; Yamazaki, Yoshio

Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.309 - 311, 2018/08

It is the report to improve the problem of flow reduction in water cooling system resolved completely in summer, 2017. It is continued the phenomenon decreasing the flow (5,800 L/min) of circulating water cooling in DTL and SDTL about 3% per week. By the flow reduction, the entire operation of J-PARC and operation of the accelerator are stopped and low flow contact of flowmeter installed in cavities. The phenomenon is progressed about 9 years since we confirm it and drastic measures for it are aspired. In this report, the point of interest to solve this problem is written. Similarly, it is suggested that the point we should be careful when we use the water cooling system it is one of the utility of J-PARC accelerator. In last summer, the flow reduction is not occur completely as specification changes and replacement of the pumps. Thanks of that, the entire operation and operation of accelerator of J-PARC is operated safety.

Journal Articles

Consideration on grease supply cycle and vibration measurement of rotating equipment

Fujirai, Kosuke; Suganuma, Kazuaki; Yamazaki, Yoshio

Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.816 - 818, 2018/08

In order to operate rotating equipment such as a cooling water pump, it is necessary to supply grease suitable for bearings of rotating equipment. The grease replenishment interval has a value recommended by the manufacturer depending on the operation time. However, an abnormal noise occurred earlier than the replenishment cycle. I thought that the current grease replenishment cycle is not suitable for maintenance and management of rotating equipment. Therefore, I tried to search for suitable grease replenishment interval using a vibration sensor installed in the cooling water pump. As a result, it was found that the replenishment interval of grease is too long according to the manufacturer recommended value and should be supplied before the vibration acceleration value increases.

Journal Articles

Performance and status of the J-PARC accelerators

Hasegawa, Kazuo; Hayashi, Naoki; Oguri, Hidetomo; Yamamoto, Kazami; Kinsho, Michikazu; Yamazaki, Yoshio; Naito, Fujio; Koseki, Tadashi; Yamamoto, Noboru; Yoshii, Masahito

Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.1038 - 1040, 2018/06

Journal Articles

Thermal desorption characteristics of several charge stripper carbon films for J-PARC RCS

Kamiya, Junichiro; Kinsho, Michikazu; Yamazaki, Yoshio; Yoshimoto, Masahiro; Yanagibashi, Toru*

Journal of the Vacuum Society of Japan, 60(12), p.484 - 489, 2017/12

Multi-turn H$$^{-}$$ charge exchange injection is employed as a beam injection method in the 3-GeV RCS (Rapid cycling synchrotron) at J-PARC (Japan Proton Accelerator Research Complex). In this method, injection H$$^{-}$$ beam is put on the same orbit as already circulating proton (H$$^{+}$$) beam in a dipole magnetic field due to the opposite curvature of the injected and circulating beams. In the straight section, where the two beams coincide with each other, both beams are passed through a thin foil, which strips two weakly bound electrons off each H$$^{-}$$ ion, forming an intense beam of protons. The thin foil, which is mostly made of carbon, would be the source of the outgassing, especially when its temperature rises due to the beam hitting. Therefore it is important to estimate the amount and components of the outgassing from the charge stripping foil. In this paper, we will report the thermal desorption measurement results for the several foil, which is used as the charge stripping foil in the RCS.

Journal Articles

Status of J-PARC accelerators

Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Hori, Yoichiro*; Yamamoto, Noboru*; Koseki, Tadashi*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1321, 2017/12

After the summer shutdown in 2016, the J-PARC restarted user operation late in October for the neutrino experiments (NU) and early in November for the materials and life science experimental facility (MLF). The beam power for the NU was 420 kW in May 2016, but increased to 470 kW in February 2017 thanks to the change and optimization of operation parameters. For the hadron experimental facility (HD), we started beam tuning in April, but suspended by a failure of the electro static septum. After the treatment, we delivered beam at the power of 37 kW. We delivered beam at 150kW for the MLF. In the fiscal year of 2016, the linac, the 3 GeV synchrotron (RCS) and the MLF were stable and the availability was high at 93%. On the contrary, the main ring has several failures and the availabilities were 77% and 84% for NU and HD, respectively.

Journal Articles

Vibration analysis of water cooling towers' defective fan bearing units at J-PARC RCS

Fujirai, Kosuke; Suganuma, Kazuaki; Yamazaki, Yoshio

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.874 - 876, 2017/12

The J-PARC (Japan Proton Accelerator Research Complex) 3-GeV RCS (Rapid Cycling Synchrotron) has many devices such as Radio-Frequency components, electromagnets and power supplies. These devices use 17MW of electricity during operation, most of which is consumed as thermal energy. Therefore, cooling water equipment is indispensable for the operation of the accelerator and its stability affects the operation rate of the accelerator. Due to resent operation experience, the bearing unit of the cooling tower fan, which is also an important part of the cooling water equipment, broke down. This accident leads to the suspension of the J-PARC operation. In order to investigate the cause of the failure, we tried to measure vibration for the defective bearing and the bearing unit were cut and observed damaged surface. As a result of the vibration measurement, it was found that vibration frequency depends on the presence or absence of scratches on the bearing. We found surface of the outer ring had scratches called flaking.

Journal Articles

Present status of water cooling system at J-PARC LINAC 2017

Suganuma, Kazuaki; Hiroki, Fumio; Ito, Takashi; Yamazaki, Yoshio

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.871 - 873, 2017/12

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.

Journal Articles

Performance and status of the J-PARC accelerators

Hasegawa, Kazuo; Hayashi, Naoki; Oguri, Hidetomo; Yamamoto, Kazami; Kinsho, Michikazu; Yamazaki, Yoshio; Naito, Fujio*; Koseki, Tadashi*; Yamamoto, Noboru*; Hori, Yoichiro*

Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2290 - 2293, 2017/06

The J-PARC is a high intensity proton facility and the accelerator consists of a 400 MeV linac, a 3 GeV Rapid Cycling Synchrotron (RCS) and a 30 GeV Main Ring Synchrotron (MR). We have taken many hardware upgrades such as front end replacement and energy upgrade at the linac, vacuum improvement, collimator upgrade, etc. The beam powers for the neutrino experiment and hadron experiment from the MR have been steadily increased by tuning and reducing beam losses. The designed 1 MW equivalent beam was demonstrated and user program was performed at 500 kW from the RCS to the neutron and muon experiments. We have experienced many failures and troubles, however, to impede full potential and high availability. In this report, operational performance and status of the J-PARC accelerators are presented.

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