Study of two nucleon interaction in nuclei with neutron capture reaction on deuterium

原子核中的双核子运动部分地受核力中的二体和三体相互作用的支配。虽然这些相互作用已经被用来解释原子核中的各种现象，但至今还没有明确的证据，特别是三体相互作用。为了研究两核子相互作用在Triton与^2H（n，np）n和^2H（n，γ）^3H反应中的作用，分离三体力的影响，我们用^7Li（p，n）^7Be反应产生的中子束进行了实验。能量范围为40至90 MeV的质子束由东北大学回旋加速器实验室提供。中子平均强度约为1 MHz，比要求的中子平均强度低百倍。反冲或发射的质子在最终状态下在活性靶中产生触发信号。来自n+^2H过程终态的γ射线和中子分别由GSO晶体和NE 213闪烁探测器探测。它们与来自活动目标的信号一致地被测量。利用本课题开发的基于VME+PC/Linux的在线数据采集系统进行数据采集，获得了初步的数据，为下一步的实验发展做了探讨。我们发现，要进行^2H（n，γ）^3H的测量以讨论原子核中两个核子的运动，需要更强的单能中子束。

Two-nucleon motions in nuclei are partially dominated by two and three body interactions in nuclear force. Although these interactions have been introduced to explain various phenomenons in nuclei, the clear pieces of evidence have not been shown yet, especially three body interaction. The aim of the study is the investigation of the role of two nucleon interaction in Triton with ^2H(n, np)n and ^2H(n,γ)^3H reaction, in order to separate the effect of three body force.We carried out the experiment using neutron beams produced by the ^7Li(p, n)^7Be reaction. The proton beams in an energy range from 40 to 90 MeV are provided from the Cyclotron laboratory, Tohoku University. The average neutron intensity was about 1 MHz that is hundred times lower than that of required.We used an active deuteron target which is made of the three layered deuterized liquid scintillator. The recoils or emitted protons in the final state produce the trigger signals in the active target. The r-rays and neutrons from the final state of the n+^2H process are detected GSO Crystals and NE213 scintillation detectors, respectively. They are measured in coincidence with the signals from the active target. The online data acquisition system based on the VME+PC/LINUX, which were developed in this project, was employed to take data.The preliminary data were obtained to discuss the development to the next stage for this experiment. We found that much intense mono-energetic neutron beams are required to carry out the ^2H(n,γ)^3H measurements to discuss two nucleon motions in nuclei.