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Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Yoshikatsu; Shinozaki, Shinichi; Fang, Z.*; Fukui, Yuji*; Mizobata, Satoshi; Michizono, Shinichiro*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.327 - 331, 2016/11
In the J-PARC linac, an intermediate-pulse with the comb-like structure is shaped by kicking an unwanted beam by the chopper cavity. Therefore, the cavities lying downstream of the RF-chopper have the beam loading with this beam shape. The present feedforward system which assumes the averaged beam current and not the comb-like beam was operated in the present LLRF, because the beam current in the linac was lower than the design value. However, it has been difficult that the required precision for the RF system is satisfied with increasing beam current. Thus, we performed the beam study of the beam loading compensation with the same shapes as the intermediate-pulses. The positive results for the cavities of SDTL and DTL with high Q values were obtained compared to the present system. On the other hand, when this compensation system was used in the case of ACS cavities, the neighbor modes were excited by the input RF. We have to improve the FF system for the operation against the real beam.
Hori, Toshihiko*; Shinozaki, Shinichi; Sato, Yoshikatsu; Mizobata, Satoshi; Fukui, Yuji*; Futatsukawa, Kenta*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.429 - 432, 2016/11
The triode klystrons with a modulating anode have been used for the J-PARC linac. Recently, we exchanged four klystrons due to the frequent discharge at a modulating anode in the klystron tube. In order to understand the discharge mechanism and to estimate the time to replace the klystron, we need to monitor the long term performance of the klystron such as the degradation of a cathode emission current and the RF gain of the klystron tube and so on. Therefore, we started to develop the klystron perveance and gain monitor module (NIM Standard one). In this paper, we will present the design concept of the monitor module, and the first performance test result using the module prototype.
Miyao, Tomoaki*; Maruta, Tomofumi*; Liu, Y.*; Miura, Akihiko
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1094 - 1096, 2016/11
no abstracts in English
Miura, Akihiko; Yoshimoto, Masahiro; Okabe, Kota; Yamane, Isao*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1102 - 1106, 2016/11
no abstracts in English
Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Fumiaki; Shinozaki, Shinichi; Chishiro, Etsuji; Hirano, Koichiro; Fang, Z.*; Fukui, Yuji*; Hori, Toshihiko; Michizono, Shinichiro*
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1320, 2015/09
In the J-PARC linac, an RF deflector installed in 3-MeV Medium Energy Beam Transport (MEBT1) is used to kick the unnecessary beam and the intermediate-pulse like a comb is created. The kicked beam leads to a scraper downstream the RF deflector and lose all kinetic energy. When the beam current increases to 50 mA of the design value, the heat load of a scraper to irradiate the kicked beam increases and its surface is predicted to be damaged. Therefore, we are preparing the tandem scrapers to reduce the damage. The half of the kicked beam leads to a scraper and the residual is to the other. The chopping operation is achieved by rotating the phase of the RF deflector in the periodic cycles by the LLRF system. We will introduce the phase rotation system and the test results.
Takei, Hayanori
no journal, ,
Frequent beam trips as experienced in existing high-power proton accelerators may cause thermal fatigue in Accelerator-Driven System (ADS) components, which may lead to degradation of their structural integrity and reduction of their lifetime. In the previous study, the thermal transient analyses were performed to investigate the effects of beam trips on the reactor components. In order to consider methods to reduce beam-trip frequency, we compared the acceptable beam-trip frequency with the performance of the ADS accelerator, which was estimated based on the operational data on existing accelerators, the Los Alamos Neutron Science Center (LANSCE) and the High Energy Accelerator Research Organization (KEK). The comparison showed that for beam trips with durations exceeding 10 s, beam-trip frequencies were about 6 to 35 times larger than acceptable values. In the present study, the operational data on J-PARC Linac were newly analyzed and probability density functions (pdf) of beam trips for the ion source and the accelerator tube of the J-PARC Linac was obtained. Using the Monte Carlo method based on the beam-trip pdf, the beam-trip frequencies of the ADS accelerator were estimated. As the result of the estimation, the beam-trip frequencies with durations exceeding 10 s were less than the previous values, but about 3 to 10 times larger than acceptable values. In the presentation, the reliability of the accelerator tube to satisfy the acceptable beam-trip frequency will be mentioned.
Takei, Hayanori
no journal, ,
Frequent beam trips as experienced in existing high-power proton accelerators may cause thermal fatigue in Accelerator-Driven System (ADS) components, which may lead to degradation of their structural integrity and reduction of their lifetime. In the previous study, the thermal transient analyses were performed to investigate the effects of beam trips on the reactor components. In order to consider methods to reduce beam-trip frequency, we compared the acceptable beam-trip frequency with the performance of the ADS accelerator, which was estimated based on the operational data on existing accelerators, the Los Alamos Neutron Science Center (LANSCE) and the High Energy Accelerator Research Organization (KEK). The comparison showed that for beam trips with a duration of 10 s or less, the beam-trip frequency was acceptable. On the other hand, for beam trips with durations exceeding 10 s, beam-trip frequencies were about 6 to 35 times larger than acceptable values. In the present study, the operational data on J-PARC Linac were newly analyzed and probability density functions (pdf) of beam trips for the ion source and the accelerator tube of the J-PARC Linac was obtained. Using the Monte Carlo method based on the beam-trip pdf, the beam-trip frequencies of the ADS accelerator were estimated. As the result of the estimation, it was found that the type of the beam-trip pdf was the initial failure type, i.e., the beam-trip frequency for the ion source and the accelerator tube was larger at the beginning and decreased monotonously with the operation time. And the beam-trip frequency of the ADS accelerator with a duration of 10 s or less was acceptable, as same as the previous value. On the other hand, beam-trip frequencies with durations exceeding 10 s were less than the previous values, but about 3 to 10 times larger than acceptable values.
Takei, Hayanori
no journal, ,
Frequent beam trips as experienced in existing high power proton accelerators may cause thermal fatigue problems in Accelerator-Driven System (ADS) components which may lead to degradation of their structural integrity and reduction of their lifetime. The comparison showed that for beam trips with durations exceeding 10 s, beam-trip frequencies were about 6 to 35 times larger than acceptable values. One of the methods to improve the reliability is redundancy which the duplication of critical components or functions of a system. In this study, technical feasibility and possibility for parallelization of the beam line were investigated for the enhanced redundancy of the ADS accelerator.
