中子活化法测量氙在塑料闪烁体表面吸附量的研究

Measurement of Quantity of Xenon Adsorbed on Surface of Plastic Scintillator by Neutron Activation Analysis Method

采用叠层式β-γ符合探测器测量弱放射性氙同位素时,由于氙在β探测器(BC404)内壁吸附而增大了其本底,影响后续弱样品的测量。利用中子活化分析法在痕量元素分析中的高灵敏度、无损等特点,采用14.1 MeV中子辐照吸附有氙的塑料闪烁体(BC404)样品,通过MCNP模拟计算和活化产物^(133) Xe和^(135) Xe特征γ射线的测量,获得了氙在塑料闪烁体表面的吸附量。结果表明:中子活化分析法能准确测量氙在塑料闪烁体表面的吸附量,其测量结果的相对合成标准不确定度约为22%。根据不确定度的来源对提高测量精度提出了具体建议。

The phoswichβ-γcoincident detector is key equipment for weak radioxenon isotope detection.Xenon will be absorbed on the surface of plastic scintillation（BC404）during measurement,and the absorption will make the detection background increase resulting in severe influences to measurement for next samples of weak-radioactivity.Neutron activation analysis（NAA）method is popular in trace analysis field because of its high sensitivity and nondestructive characteristic.In this paper,quantity of absorbed xenon was determined based on MCNP simulation on theγ-ray peaks of ^133 Xe and ^135 Xe produced by（n,2n）reaction.The results show that NAA is a feasible method for measurement xenon absorbed on BC404 surface.The relative standard uncertainty ofvalue is about 22%.Some suggestions for suppressing the standard uncertainty of the data are also proposed according to the source of uncertainty.