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J-PARC負水素イオン源の運転状況

Operation status of the J-PARC H$$^{-}$$ ion source

小栗 英知; 上野 彰; 池上 清*; 滑川 裕矢; 大越 清紀

Oguri, Hidetomo; Ueno, Akira; Ikegami, Kiyoshi*; Namekawa, Yuya; Okoshi, Kiyonori

J-PARCで稼動中のLaB$$_{6}$$フィラメント駆動型負水素イオン源は、加速器ビームスタディの内容により、高出力(約30mA)と低出力(約5mA)の運転を交互に行っている。運転開始から現在までの約3年の間、イオン源トラブルによる加速器ビーム停止時間は延べで50時間程度であり、イオン源の稼働率は現状、98%以上である。初期のトラブルはおもにフィラメントの不具合によるものであったが、フィラメント構造の改良を重ねた結果、現在では2030時間(うち高出力運転が780時間,低出力運転が250時間)のフィラメント連続使用実績を得ている。また、高出力モード運転時のビーム電流減少率は-0.4mA/dayと低く、イオン源オペレータによるビーム電流調整操作は1日1回程度である。本イオン源は、長時間フルスペック運転の実証など幾つかの課題がまだ存在するが、おおむね実用機として十分なビーム性能と信頼性を有していると言える。

A cesium-free H$$^{-}$$ ion source driven with a LaB$$_{6}$$ filament is being operated for J-PARC. The beam commissioning of J-PARC accelerators started in November 2006. As of June 2009, there have been 25 beam commissioning or supply runs. In these runs, the ion source has been successfully operated in two different modes. One is a low beam current mode, in which approximately 5 mA is produced. The other is a high beam current mode, in which approximately 30 mA is produced. According to the task of the run, one of the two modes was selected. Since the beam current can be maintained within a few percent errors by tuning the ion source parameter once a day, 24 hours beam operation with an ion source operator only in day time was started in April 2008. The total interruption time during the runs due to the ion source failure is approximately 50 hours as of June 2009. The availability of the ion source is calculated to be 99%. The interruptions were mainly caused by the insufficient lifetime of the filament. By a few modifications on the filament shape administered until August 2007, we succeeded in achieving the lifetime of 2,030 hours, which included 1,250 hours in the low beam current mode and 780 hours in the high beam current mode.

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