High spin isomer beam experiment at RIKEN

Abstract

Development of HSIB (High Spin Isomer Beam) and secondary nuclear fusion experiment have been planned in order to produce the very high spin state in the RIKEN (Institute of Physical and Chemical Research) Accelerator Research Facilities. Using the reactions of Mg-24(Xe-136,alpha 9n)Gd-147m and C-12(Gd-147m,xn)Yb-(159-x), the yield of HSIB and the effectiveness of rotation target system were confirmed under the high intensity primary beam. The Xe beam was accelerated to 8.5 MeV/u by RIKEN Ring Cyclotron. The maximum intensity of the Xe beam was 260 pnA. HSIB was separated from the primary beam and transported to the final focal plane by RIPS (RIKEN Projectile fragment Seperator). The rotating target system was operated under the 160 pnA and 260 pnA intensities. The yield of HSIB was almost constant during the operation: around 6.5 x 10(exp 3) in the 160 pnA intensity and 1.5 times larger yield of HSIB was obtained in the 260 pnA run. The efficiency calibration of Ge telescope system was also made by using Eu-152 standard source. The efficiency of the Ge telescope system was almost constant (about 2.5 x 10(exp -4)) in the high energy region, i.e. higher than 500 keV.

非常に高いスピン状態をつくり出すために、HSIB(高スピン異性核ビーム)の開発と2次核融合実験がRIKEN(理化学研究所)の加速器施設で計画されている。Mg-24(Xe-136,α9n)Gd-147m反応とC-12(Gd-147m,xn)Yb-(159-x)反応を用いて、高い強度の1次ビームで、HSIBの収量と回転標的装置の有効性の確認をした。RIKENリングサイクロトロンによりXeビームを核子当たり8.5MeVに加速した。この時の、ビームの最大強度は260pnAであった。HSIBを1次ビームから分離し、入射核破砕片分離装置(RIPS)により最終焦点面に移送した。回転標的装置を160pnAと260pnAのビーム強度条件下で操作した。HSIBの収量は操作中0ほぼ一定で、強度が160pnAの条件で6.5×10(exp 3)、260pnAの条件では1.5倍のHSIBが得られた。Geテレスコープ装置の効率の校正を、Eu-152標準線源を用いて行った。Geテレスコープ装置の効率は高いエネルギー領域(500keV以上)においてほぼ一定(2.5×10(exp -4))であった。