Status of the J-PARC 3 GeV RCS

大強度陽子加速器施設J-PARC 3GeVシンクロトロンの現状

金正 倫計  

Kinsho, Michikazu

大強度陽子加速器施設(J-PARC)の3GeVシンクロトロン(RCS)は先の東日本大震災で多大な被害を受けた。RCSは2008年の利用運転開始から順調にビーム強度を増加させ、震災当日は、主リング(MR)に300kW相当、物質生命科学実験施設(MLF)には220kWのビームを供給していた。震災後復旧作業を順調に実施し、2011年12月17日にはRCSでビーム試験が可能となった。22日には震災前と同じ強度のビームをMLFへ取り出した。震災後再稼働までの間、復旧作業のみならず、改造も行い、さらに安定でビームロスの少ない運転が可能となった。さらに、復旧作業のみならず、性能向上のための作業を実施した。特に、入射部にコリメータを設置し、ビームロスを1桁低減させた。また、420kW相当の試験運転にも成功した。

The J-PARC rapid cycling synchrotron (RCS) was heavily affected by the last Great East Japan Earthquake. The damage to each device was investigated and an attempt was made to restore them, with successful beam commissioning of the RCS beginning on 17th December 2011. On the 22nd, a 3 GeV beam was extracted to the MLF with beam currents that approached those obtained before the earthquake. Not only the recovery, but also an improvement of the RCS has been achieved, enabling high-power stable operation with low beam losses. Specifically, downstream beam losses due to the charge exchange foil were localized by installing a new collimator at injection area. As a result, the residual activation of this area was reduced by one order of magnitude and created the possibility of a higher beam power for the RCS. In a recent high-intensity trial of the RCS with a 420 kW equivalent intensity beam, significant progress toward design output beam power of 1 MW was demonstrated.