Heavy-ion induced fission in the medium energy region

Abstract

The difference in the mass distributions, under the conditions that the incident energy was below and above the critical energy correspondent to a critical angular momentum, has been studied in order to investigate a change in the fission phenomena affected by the onset of FaF (Fast Fission), which means the fission without barrier. A gold target was bombarded with O-16 ions. The irradiated samples were analyzed by means of non-destructive gamma-ray spectrometry with Ge detectors. The resulting mass distributions for the reactions of Au-197 with O-16 at 127 MeV and 156 MeV of the incident energy were shown in figures. The fusion fission mass distribution at 156 MeV should be well approximated by the mass distribution at 127 MeV under the assumptions that the FaF does not exist below the critical energy. The fusion fission cross sections for 157 MeV were deduced on the basis of the distribution obtained at 127 MeV.

無障壁核分裂を意味する高速核分裂(FaF)開始の影響を受ける核分裂現象の変化を調べるため、入射エネルギーが臨界角運動量に対応する臨界エネルギー以下および以上の時の質量分布の相違点を研究した。金ターゲットをO-16イオンで衝撃を与えた。照射した試料をゲルマニウム検知器を備えた非破壊γ線分光分析を用いて分析した。入射エネルギーが127MeVと156MeVにおけるAu-197とO-16の反応に対する質量分布の結果を図に示した。FaFは臨界エネルギー以下では存在しないという仮定の基では、入射エネルギー156MeVにおける核融合・核分裂質量分布は127MeVの質量分布を用いて十分に近似可能のはずである。127MeVの質量分布に基づいて157Mevにおける核融合・核分裂断面積を導き出した。