Photodisintegration of deuterium by linearly polarized gamma rays

产业技术综合研究所存储环TERAS中的Nd:YVO_4激光器的线偏振光子与相对论性电子发生逆康普顿散射，产生线偏振γ射线。用 2.5 和 3.0 MeV 的偏振 γ 射线束照射封装的氘化液体闪烁体 (BICRON BC-537)。目标闪烁体充当主动目标。四个中子探测器，每个由五个嵌入聚乙烯中的 ^3He 正比计数器组成，安装在与 y 射线束成 90° 的位置；一对中子探测器平行于线偏振γ射线的电场安装，另一对垂直于电场安装。在氘的光分解过程中观察到各向异位中子发射。由各向异性求出氘的光分解中的M1成分和E1成分的比例。使用蒙特卡罗代码 MCNP 模拟探测器之间的中子事件串扰。数据分析中考虑了串扰效应。发现该比率与两种能量下的理论预测一致。我们将对氘在与大爆炸核合成直接相关的能量区域中的 M1 和 E1 光解体进行系统测量。

Linearly polarized γ rays were produced in the inverse Compton scattering of linearly polarized photons from a Nd : YVO_4 laser with relativistic electrons in the storage ring TERAS at the National Institute of Advanced Industrial Science and Technology. An encapsulated deuterated liquid scintillator (BICRON BC-537) was irradiated with polarized γ ray beams at 2.5 and 3.0 MeV. The target scintillator served as an active target. Four neutron detectors, each consisting of five ^3He proportional counters embedded in a polyethylene were mounted at 90° with respect to the y-ray beam; a pair of neutron detectors was mounted parallel to the electric field of the linearly polarized γ rays and the other pair was mounted perpendicular to the electric field. Anisotopic neutron emissions were observed in the photodisintegration of deuterium. The ratio of M1 and E1 components in photodisintegration of deuterium was determined from the anisotropy. Cross talks of neutron events between the detectors were simulated with a Monte Carlo code MCNP. The cross-talk effect was taken into account in the data analysis. It was found that the ratio is consistent with theoretical predictions at both energies. We will perform a systematic measurement of the M1 and E1 photodisintegration of deuterium in the energy region of direct relevance to big bang nucleosynthesis.