RRC and AVF cyclotron operations

Abstract

The distribution of many kinds of beams are shown on an energy-mass space, which were accelerated with RRC (RIKEN (Institute of Physical and Chemical Research) Ring Cyclotron) in the annual period from January to December 1997. Among them, beams which were tried for the first time, or whose intensities were remarkably improved during this period, are listed in a table together with their acceleration data. In the summer of 1997, several improvements were made on a preinjector of RILAC (RIKEN Linear Accelerator). As the result, beam intensities higher than the officially restricted upper limit of beam intensity were achieved. The petition to increase this restricted number was permitted by the government at the end of the year; therefore it will become possible to make the experiment of super-heavy element research more efficiently in the following year on. Bi-209, which is the heaviest ion for the case of RILAC-RRC operation, and Pb-208 were accelerated up to 15 MeV/nucleon to be used for nuclear physics experiments, and Kr-84 which is the heaviest ion for the case of AVF (Azimuthally Varying Field)-RRC operation was successfully accelerated up to 70 MeV/nucleon for biomedical experiments. As the result, the beam available regions in the energy-mass map have covered up all the area. For the production of metallic-ion beams, a new method MIVOC (Metal Ion from Volatile Compounds) was tried with the 18 GHz ECR (Electron Cyclotron Resonance) ion source, resulting in a remarkable improvement on the intensity. A total of operation hours of the year amounted to 6,500 hr, where 4,500 hr were spent for experiments. Most of the beam time (75 percent) was devoted to the nuclear physics experiments, the rest (25 percent) was devoted to the other fields such as medical science, radio-chemistry, and so on. A total of beam time for the stand-alone use of AVF cyclotron amounted to 700 hr. In order to increase the total efficiency in the RILAC-RRC operation, improvements have been made. As the result, the beam transmission efficiency through RRC as well as the beam stability was improved successfully.

1997年1月から12月までの1年間にRRC(RIKEN(理化学研究所)リングサイクロトロン)で加速した多種類のビームをエネルギー・原子量図上に示した。これらの中で、この期間に初めて加速を行ったもの、およびビーム強度の向上が著しいものをその加速データと共に表に示した。1997年夏にRILAC(RIKEN線形加速器)の前段入射器に若干の改善を行い、その結果、規制上限値以上のビーム強度を実現できるようになった。この規制上限値を上げる申請が年末に許可になったので、来年以降は、超重元素の研究をさらに効率良く行うことができる。RILAC-RRC運用で最も重いBi-209およびPb-208が核物理学実験用の15MeV/核子まで加速でき、AVF(周回変動磁場型)-RRC運用で最も重いKr-84は生体臨床医学実験用の70MeV/核子までの加速に成功した。その結果、エネルギー・原子量図上のビーム利用範囲の全域を実現できるようになった。金属イオンビームの生成のために、新しいMIVOC(揮発性化合物からの金属イオン)法を18GHzECR(電子サイクロトロン共鳴)イオン源を用いて試み、かなりの強度改善に成功した。1997年の全運用時間は6,500時間に達し、その内4,500時間を実験に利用し、その75%が核物理学実験で残り25%が医科学、放射線化学などの実験であった。AVFサイクロトロン単体使用のビーム利用時間は700時間に達した。RILAC-RRC運用における全体効率を向上するために改善を実施してきた結果、RRC全体のビーム伝達効率とビーム安定性の向上に成功した。