Photodisintegration of deuterium by linearly polarized gamma rays

在国家先进工业科学技术研究所的存储环TERAS中，用相对论电子的Nd: YVO_4激光器对线偏振光子进行逆康普顿散射，产生线偏振γ射线。用2.5和3.0 MeV的极化γ射线照射封装的氘化液体闪烁体（BICRON BC-537）。目标闪烁体作为主动目标。四个中子探测器，每个由嵌入聚乙烯的5 ^3He比例计数器组成，安装在相对于y射线束的90°；一对中子探测器平行于线极化γ射线的电场安装，另一对探测器垂直于电场安装。在氘的光分解过程中观察到各向异性中子发射。从各向异性角度确定了氘光分解过程中M1和E1组分的比值。用蒙特卡罗程序MCNP模拟了探测器间中子事件的串扰。在数据分析中考虑了串扰效应。在两种能量下，该比值与理论预测一致。我们将在与大爆炸核合成直接相关的能量区域对氘的M1和E1光分解进行系统测量。

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.