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Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.
JAEA-Technology 2023-005, 33 Pages, 2023/05
JAEA-Technology-2023-005.pdf:5.25MB
During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.
Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Hara, Keigo*; Hasegawa, Katsushi*; Sugiyama, Yasuyuki*; et al.
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.840 - 844, 2021/10
The J-PARC RCS employs the dual-harmonic operation, in which the fundamental and the second harmonic RF voltages are used for the beam acceleration. The each harmonic voltage and phase applied for the acceleration gaps are controlled by the multiharmonic vector RF voltage control system using the signal from the cavity gap voltage monitor equipped with the one of the acceleration gaps of the each RF cavity. Since the bunch shape varies depending on the relative phase of each harmonic, it is important to evaluate the frequency response of the cavity gap voltage monitor. The measurements of frequency response of the cavity gap voltage monitor and beam tracking simulation considering the measurement were carried out. As a result, it was confirmed that the bunch shape of the beam tracking simulation reproduces the one measured at the 1MW beam operation well. The details of the frequency response measurement, the beam tracking simulation and the discussion of the cavity gap voltage monitor circuit are reported.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Yamamoto, Masanobu; Okita, Hidefumi; Omori, Chihiro*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.170 - 174, 2021/10
A stable and precise LLRF (Low Level RF) control system is indispensable for acceleration of high intensity proton beam in the J-PARC RCS. The original LLRF control system had been operated without major problems for more than ten years since the start of operation of the RCS, while maintenance of the system became difficult due to the obsolesce of the old FPGAs in the modules. We developed and installed the next-generation LLRF control system based on MTCA.4. The key function of the system is the multiharmonic vector rf voltage control feedback. We describe the system overview and the commissioning results. The performance of the beam loading compensation is significantly improved.
Nomura, Masahiro; Okita, Hidefumi; Shimada, Taihei; Tamura, Fumihiko; Yamamoto, Masanobu; Furusawa, Masashi*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; Hara, Keigo*; Omori, Chihiro*; et al.
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.80 - 82, 2021/10
no abstracts in English
Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.3020 - 3022, 2021/08
In the J-PARC RCS, the dual-harmonic operation, in which each RF cavity is driven by superposition of the fundamental accelerating voltage and the second harmonic voltage, are employed. The dual-harmonic-operation significantly improves the bunching factor and is indispensable for acceleration of the high intensity beams. The original LLRF control system was replaced with the new system in 2019, which can control the amplitudes of the higher harmonics as well as the fundamental and second harmonics. Therefore we consider to use additionally the third harmonic voltage for further improvement of the bunching factor during acceleration. By the triple-harmonic operation, the flat RF bucket can be realized and beam simulation results indicate that the bunching factor can be improved about 30% at maximum. In this presentation, we describe the longitudinal simulation studies of the triple-harmonic operation. Also the preliminary test results are presented.
Yamamoto, Masanobu; Okita, Hidefumi; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; et al.
Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.1884 - 1886, 2021/08
Tetrode vacuum tubes in J-PARC RCS are used under a reduced filament voltage condition compared with the rating value to prolong the tube lifetime. For the first time after 60,000 hour of operation in the RCS, one tube has reached the end of its life in 2020. Therefore, the reduced filament voltage works well because the tube has been running beyond an expected lifetime suggested by the tube manufacturer. However, the reduced filament voltage decreased the electron emission from the filament. Although the large amplitude of the anode current is necessary for the high intensity beam acceleration to compensate a wake voltage, a solid-state amplifier to drive a control grid circuit almost reaches the output power limit owing to the poor electron emission from the filament. We changed the filament voltage reduction rate from 15% to 5%. The required power of the solid-state amplifier was fairly reduced, whereas the accelerated beam power remained the same. We describe the measurement results of the vacuum tube parameters in terms of the filament voltage tuning.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Yamamoto, Masanobu; Okita, Hidefumi; Omori, Chihiro*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Nuclear Instruments and Methods in Physics Research A, 999, p.165211_1 - 165211_11, 2021/05
Times Cited Count：5 Percentile：65.59(Instruments & Instrumentation)The low level rf (LLRF) control system has key roles for the stable acceleration of the high intensity beam. The original LLRF control system for the RCS of J-PARC has been working nicely without major issues for more than ten years since the operation of the RCS started in 2007. Due to the obsolescence of the key digital devices, it is difficult to maintain the original system for a longer period, therefore we developed the next-generation LLRF control system. All of the LLRF functions of the new system were tested and commissioned. In this article, we describe the commissioning of two key functions, the phase feedback and the multiharmonic vector rf voltage control feedback for twelve cavities. The commissioning methodologies and beam test results are presented. The stable acceleration of the high intensity beam at the design intensity of 
ppp is achieved. The next-generation LLRF control system has been successfully deployed and commissioned.
Yamamoto, Masanobu; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Nomura, Masahiro; Omori, Chihiro*; Shimada, Taihei; Sugiyama, Yasuyuki*; Tamura, Fumihiko; Yoshii, Masahito*
JPS Conference Proceedings (Internet), 33, p.011022_1 - 011022_6, 2021/03
A Tetrode vacuum tubes (Thales TH589) are used in the J-PARC ring rf system. The operation has started in 2007, and the total operation time is more than 50,000 hours. There is no tube which reaches the end of life except an initial failure in the 3 GeV synchrotron. TH589 has a thoriated tungsten filament and it is carburized to suppress an evaporation of the thorium. The resistance of the filament decreases through the decarburization process after the filament operation has started. The tube constructor suggests that reduced filament voltage up to 10% compared with the rated value is effective to suppress the decarburization. However, the filament current increases even though the voltage is kept constant due to the resistance reduction, and it is observed that an increment of the power dissipation promotes the decarburization. This means that keeping the filament voltage constant is not enough; keeping the power dissipation constant is necessary to prolong the tube life time, and we employ a procedure to decrease the current regularly.
Nomura, Masahiro; Tamura, Fumihiko; Shimada, Taihei; Yamamoto, Masanobu; Furusawa, Masashi*; Sugiyama, Yasuyuki*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Yoshii, Masahito*
Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.64 - 67, 2020/09
Image recognition using a convolutional neural network (CNN) has been used in a wide range of fields and has produced excellent results. If this image recognition technology is used effectively, it should be possible to obtain information from an image equal to or more than the information that a person can obtain from an image. At J-PARC, researchers with specialized knowledge obtain beam information needed to adjust the equipment from an image called mountain plot. In this study, we applied the image recognition technology by using CNN to this mountain plot image, and tried to obtain the information about the beam necessary for adjustment. As a result, we were able to obtain more information than is currently available by using the image recognition technology. In the future, we plan to adjust the equipment based on the information actually obtained from the image recognition technology and confirm its effectiveness
Okita, Hidefumi; Tamura, Fumihiko; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; Hara, Keigo*; et al.
Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.674 - 678, 2020/09
Longitudinal beam simulation code BLonD (Beam Longitudinal Dynamics), which has been developed by CERN in recent years, is being used accelerator facilities around the world. BLonD can simulate longitudinal beam motion considering with wake voltage and space charge effect and is written by Python, which makes it highly readable and general-purpose code. We are currently conducting a benchmark of BLonD aiming at studying for further improvements of acceleration technology and stable operation of the J-PARC 3GeV synchrotron (RCS). The bunching factor, which express the longitudinal beam charge distribution, calculated by BLonD simulation reflected by the current 1MW beam operation parameters reproduce the experimental results well and the validity of BLonD for RCS longitudinal beam simulation was confirmed.
Tamura, Fumihiko; Yamamoto, Masanobu; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Omori, Chihiro*; Shimada, Taihei; Nomura, Masahiro; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*
Journal of Physics; Conference Series, 1350(1), p.012189_1 - 012189_7, 2019/12
Times Cited Count：1 Percentile：52.28(Physics, Particles & Fields)Magnetic alloy cavities are employed in the J-PARC RCS to generate high accelerating voltages. The cavity, which is driven by a vacuum tube amplifier, has a wideband frequency response and the beam loading in the cavity is multiharmonic. Therefore, the tube must generate a multiharmonic output current. An LTspice circuit model is developed to analyze the vacuum tube operation and the compensation of the multiharmonic beam loading. The model includes the cavity, tube amplifier, beam current, and LLRF feedback control. The feedback control consists of the I/Q demodulator including low pass filters, PI control, and I/Q modulator. In this presentation, we present the implementation of the LLRF functions in the LTspice simulations. The preliminary simulation results are also presented. The simulations fairly agree with the beam test results.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Yamamoto, Masanobu; Omori, Chihiro*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*
Physical Review Accelerators and Beams (Internet), 22(9), p.092001_1 - 092001_22, 2019/09
Times Cited Count：5 Percentile：47.88(Physics, Nuclear)Beam loading compensation in the rf cavities is a key for acceleration of high intensity beams in 3 GeV RCS of the J-PARC. Since we employ wideband magnetic alloy rf cavities for the J-PARC RCS and the wake voltage contains several harmonics, a multiharmonic beam loading compensation is required. The multiharmonic rf feedforward for the most important six harmonics is implemented in the existing low level rf (LLRF) control system, which has been working fairly well for acceleration of high intensity beams of up to 1 MW. However, we found the degradation of the performance for compensation of the feedforward with very high intensity beams. Therefore, a multiharmonic vector rf voltage control has been developed. The detail of system configuration, commissioning methodology, and beam test results using very high intensity beams are described. The beam loading by the 1 MW equivalent beam in the cavity is successfully compensated.
Nomura, Masahiro; Tamura, Fumihiko; Shimada, Taihei; Yamamoto, Masanobu; Furusawa, Masashi*; Sugiyama, Yasuyuki*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Yoshii, Masahito*
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.258 - 261, 2019/07
In recent years, summer temperatures have tended to increase, so understanding the amount of power consumption in summer from weather information has become important in terms of contract power and power saving measures. The relationship between the amount of power consumption and weather conditions is that the accelerator facility has many cooling facilities, so it can be thought that the amount of power used to cool each device increases as the temperature and humidity increase. It seems that it has not been investigated specifically what kind of dependence there is. Therefore, considering the neural network as a kind of fitting function or a model of calculation, we investigated the influence of weather conditions on the power consumption. As a result, it was found that the power consumption of the accelerators mostly depends only on the temperature, and the electric power of Linac and RCS increases by about 1 MW when the temperature of Mito rises by 10
C.
Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Yoshii, Masahito*
Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.2017 - 2019, 2019/06
J-PARC RCS has successfully accelerated 1 MW proton beam, and we have considered acceleration with the next target being 1.2 MW. An issue for 1.2 MW beam acceleration is the rf system. The present anode power supply is limited by its output current, and the vacuum tube amplifier suffers from an unbalance of the anode voltage swing, arising from the combination of multi-harmonic rf driving and push-pull operation. We have investigated the mitigation of the maximum anode currents and unbalanced tubes by choosing appropriate circuit parameters of the rf cavity with tube amplifier. We describe the analysis results of the vacuum tube operation for 1.2 MW beam acceleration in the RCS.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Shimada, Taihei; Nomura, Masahiro; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*
Journal of Physics; Conference Series, 1067, p.072030_1 - 072030_6, 2018/10
Times Cited Count：3 Percentile：79.15(Physics, Particles & Fields)Vector RF voltage feedback control for the wideband magnetic alloy cavity of the J-PARC RCS is considered to be employed to compensate the heavy beam loading caused by high intensity proton beams. A prototype system of multiharmonic RF vector voltage control has been developed and is under testing. To characterize the system performance, full RF simulations could be performed by software like Simulink, while the software is proprietary and expensive. Also, it requires much computing power and time. We performed the simplified baseband simulations of the system in z-domain by using free software, Scilab and Python control library. It seems to be beneficial for searching the parameters that the baseband simulation can be performed quickly. In this presentation, we present the setup and results of the simulations. The simulations well reproduce the open and closed loop responses of the prototype system.
Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Tamura, Fumihiko; Furusawa, Masashi*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Sugiyama, Yasuyuki*; Yoshii, Masahito*
Journal of Physics; Conference Series, 1067, p.052014_1 - 052014_6, 2018/10
Times Cited Count：3 Percentile：79.15(Physics, Particles & Fields)The J-PARC RCS employs Magnetic Alloy (MA) loaded cavities. The RF power is fed by vacuum tubes in push-pull operation. We realize multi-harmonic RF driving and beam loading compensation thanks to the broadband characteristics of the MA. However, the push-pull operation has disadvantages in multi-harmonics. An unbalance of the anode voltage swing remarkably appears at very high intensity beam acceleration. We propose a single-ended MA cavity for the RCS beam power upgrade, where no unbalance arises intrinsically.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*
Proceedings of 15th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1131 - 1135, 2018/08
The LLRF control system for the J-PARC RCS has been playing important roles for acceleration of high intensity proton beams. The key functions of the system are the dual harmonic voltage control and the multiharmonic rf feedforward to compensate the heavy beam loading in the wideband cavities. The system has been working fine for more than ten years, however, the old FPGAs in the system are already discontinued and not supported by current development environment. Maintenance of the system will be difficult soon. We are developing the next generation LLRF control system with the new form factor, MicroTCA.4, while the existing system is based on the VME. In this article, we describe the configuration of the new system, its functions, and the status of the development.
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.241 - 245, 2017/12
Beam loading compensation in magnetic alloy (MA) cavities is necessary to accelerate high intensity proton beams in the J-PARC 3GeV rapid cycling synchrotron (RCS). Because of its wide frequency response, wake voltages in the cavity by the beam contain multiharmonic components and the beam loading compensation must be multiharmonics. The J-PARC RCS utilize the multiharmonic rf feedforward system for the beam loading compensation. Although the performance of the feedforward is good, we have found some limitations of performance due to the open loop configuration of the feedforward system. For the next generation LLRF control system for the RCS, we consider to employ vector rf control in addition to the feedforward for beam loading compensation. We developed a prototype of the vector rf control. The system details, commissioning methodology, and preliminary beam test results are presented.
Nishimura, Akihiko; Takenaka, Yusuke*; Furusawa, Akinori; Torimoto, Kazuhiro; Ueda, Masashi; Fukuda, Naoaki*; Hirao, Kazuyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.52 - 59, 2017/08
no abstracts in English
