High-power test and thermal characteristics of a new radio-frequency quadrupole cavity for the Japan Proton Accelerator Research Complex linac

J-PARCリニアックのためのRFQ空洞の大電力試験と熱的性質

近藤 恭弘   ; 森下 卓俊  ; 長谷川 和男; 千代 悦司; 平野 耕一郎  ; 堀 利彦; 小栗 英知  ; 佐藤 文明; 篠崎 信一 ; 杉村 高志*; 川又 弘史*; 内藤 富士雄*; 福井 佑治*; 二ツ川 健太*; 南茂 今朝雄*

Kondo, Yasuhiro; Morishita, Takatoshi; Hasegawa, Kazuo; Chishiro, Etsuji; Hirano, Koichiro; Hori, Toshihiko; Oguri, Hidetomo; Sato, Fumiaki; Shinozaki, Shinichi; Sugimura, Takashi*; Kawamata, Hiroshi*; Naito, Fujio*; Fukui, Yuji*; Futatsukawa, Kenta*; Nammo, Kesao*

J-PARCリニアックのための新しいRFQ (RFQ II)の大電力試験を行った。RFQ IIは、運転中のRFQに放電問題が起きたため、予備のRFQとして開発された。まず、RFQ IIのコンディショニングが行われ、50時間のコンディショニング後に既定の330kW, 3%デューティで非常に安定になった。次に、RFQ IIは冷却水の温度を調整することで周波数を調整するので、熱的性質を測定した。周波数応答を測定し、FEMモデルと比較し、良い一致が得られた。時間応答もシミュレーションと実験で一致した。また、RF負荷を変えた時の電磁場の変化を調べ、問題ないことを確認した。

We performed a high-power test of a new radio-frequency quadrupole (RFQ II) for the J-PARC linac. RFQ II was developed as a spare RFQ because the operating J-PARC RFQ has suffered from a sparking problem. First, the conditioning of RFQ II was carried out; after 50 h of conditioning, RFQ II became very stable with a nominal power and duty of 330 kW and 3%, respectively. Next the thermal properties were measured because the resonant frequency of RFQ II is tuned by changing the temperature of the cooling water. The frequency response was measured and compared to finite-element method simulation results, confirming that the simple two-dimensional model reproduces the experimental data well. The differences in the field distribution with changes in the rf loading and the cooling-water temperature were also measured, and no serious field distortion was observed. Therefore, we conclude that RFQ II can perform well as a high-power rf cavity.