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タイトル: Development of a New RF Accelerating Cavity Loaded with Magnetic Alloy Cores Cooled by a Chemically Inert Liquid for Stabilizing and Enhancing the Performance of J-PARC Ring Accelerator
その他のタイトル: J-PARCリング加速器の安定化及び性能増強に向けた不活性冷媒液冷式による金属磁性体コア装荷の新型高周波加速空胴の開発
著者: Morita, Yuichi
著者(別言語): 森田, 裕一
発行日: 2011年3月24日
抄録: J-PARC (Japan Proton Accelerator Research Complex) is a proton accelerator constructed in Tokai-mura, Ibaraki, Japan. J-PARC was designed to produce the world's most intensive proton beam and provide it to advanced research facilities for the wide range of field. T2K (from Tokai to Kamioka) is one of the most important experiment. It is a long baseline neutrino experiment. It requires 5×10(21)POT in approximately 5 years which corresponds to 0.75[MW]. To produce proton beam of this intensity, the repetition rate of the accelerator is planed to be increased. This method requires the accelerating gradient to be enhanced, so that the accelerating cavity will be put in the hard environment to accelerate a large beam current in a long term. A powerful and stable accelerating cavity is indispensable. The presently installed cavities are loaded with cores made of "FINEMET". FINEMET is a magnetic alloy which is produced by Hitachi Metals, Ltd.. A stable operation of the presently installed cavities in Rapid-Cycling Synchrotron (RCS) has not established yet, because they have a problem that the FINEMET cores are damaged while the cavities are in operation. We are developing a new accelerating cavity which can realize the stable and powerful operation. We simulated the thermal stress in the core, and performed a test of compressing samples of the core. The cause of the damage was identified as a buckling which was caused by the thermal stress in the core. We showed the core without impregnation is favorable to prevent the buckling. The development of the new cavity is based on these results. The cores for the new cavity have unique structures. They are not impregnated and each core is radially separated into three. Fluorinert is used as the coolant. Fluorinert is a chemically inert liquid, so that it is suited for cooling FINEMET cores which is subject to corrosion. Fluorinert flows in the flow channel which is formed on the surfaces of the radially separated cores. The flow channel makes Fluorinert turbulent, so that a high cooling efficiency is realized. We designed RF structure of the cavity and the flow channel with FEM (Finite Element Method) simulators. We assembled a prototype of the new cavity, and prepared the test facility. This is the first case to use three dimensional FEM simulators for developing a cavity loaded with magnetic alloy cores. We measured the resonance frequency, the shunt impedance and the Q factor of the prototype cavity and verified they satisfied the requirements of RCS. The temperature on the surface of the small core was measured with the thermo paint. The value was consistent to that was obtained from the simulation. The effective heat transfer coefficient was obtained by measuring the time constant of the temperature decrement of Fluorinert, and the value was consistent to that was obtained from the simulation in 20% . The heat transfer coefficient on the surface of the small core was obtained with the simulation. The value is consistent to that was calculated with the empirical equation. The value surpassed that of presently installed cavity over 60[L/min]. We supplied the power to the prototype cavity up to 10[kW], and it worked stably. This is the first development of the cavity loaded with magnetic alloy cores, which is able to be operated stably with the large input power of 10[kW] per core. Adopting this new cavity is the most realistic way to stabilize and enhance the performance of the J-PARC ring accelerators.
内容記述: 報告番号: 甲26662 ; 学位授与年月日: 2011-03-24 ; 学位の種別: 課程博士 ; 学位の種類: 博士(理学) ; 学位記番号: 博理第5607号 ; 研究科・専攻: 理学系研究科物理学専攻
URI: http://hdl.handle.net/2261/51146
出現カテゴリ:021 博士論文
1150220 博士論文(物理学専攻)

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