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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

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

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

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

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.

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