Gamma-ray linear polarization measurement by segmented Ge

Abstract

Linear polarization measurements of gamma-rays in Nd-143 and Sm-145 were performed by using La-139(B-10,4n)Sm-145 and Te-130(O-18,5n)Nd-143 reactions. The B-10 and O-18 beams of 50 and 80 MeV, were provided by Kyushu University tandem accelerator and the SF (Spin Flip) cyclotron of KEK (High Energy Accelerator Research Organization)-Tanashi, respectively. The segmented Ge detector was placed at 70 mm from a target. The spectra were made by adding coincident signals of two segments aligned in beam parallel X or perpendicular Y direction. The linear polarization information can be obtained from a ratio (N(sub X)/N(sub Y)) of concerned peaks in these spectra. It was shown that the ratios, which correspond to the gamma-rays energy in Sm-144 emitted through 880 ns isomer. The result for Sm-145 and Nd-143 were compared with ones that is previously measured. Previously known electric and magnetic characters of these gamma-rays were reproduced in the present experiments.

La-139(B-10,4n)Sm-145とTe-130(O-18,5n)Nd-143反応を用いて、Nd-143とSm-145におけるγ線の直線偏波測定を行った。50MeVと80MeVのB-10とO-18ビームは九州大学のタンデム型加速器とKEK(高エネルギー加速器機構)-TanashiのSF(スピンフリップ)サイクロトロンによって供給された。セグメント化Ge検出器は標的から70mmの位置に置いた。ビーム軸に平行なX方向あるいは垂直なY軸方向に並んだ2つのセグメントからの同時シグナルを加えてスペクトルを形成する。これらスペクトルの該当するピーク計数値の比(N(sub Y)/N(sub X))から直線偏波に関する情報が得られる。半減期が880nsである異性核から放出されたSm-144のγ線エネルギーに対応するN(sub Y)/N(sub X)比を示した。また、Sm-145とNd-143の結果について、以前の測定結果と比較した。これらの結果について、この実験はこれらのγ線の電気的、磁気的特徴を再現した。