PRECISE AND HIGHLY PRECISE MEASUREMENT OF GAMMA-RAY EMISSION PROBABILITY

利用实时二维数据采集系统，用πβ-γ符合仪精确测量了γ射线发射概率，结果表明，^<76>As, ^<159>Gd, ^<169>Yb, ^<182>Ta, ^<186>Re, ^<187>W和^<188>Re的确定度提高了两个以上因素。此外，报告的^<76>As和^<169>Yb的值分别被高估了10%和2%，而^<159>Gd、^<187>W和^<188>Re的值分别被低估了5%、20%和3-10%。本文对相对效率为25%的HPGe探测器的γ射线探测效率曲线进行了高精度测定，在源-探测器距离30 cm处，在吸收和级联求和校正较小的条件下，测量了发射两个高概率级联γ射线的标准光源。消息来源^ < 24 > Na, ^ < 46 > Sc, ^ < 48 > Sc, ^ < 60 >有限公司^ 8 y ^ < 94 > Nb, ^ < 108 > Ag)和^ < 111 >。分析了能量与检测效率的关系，采用协方差矩阵最小二乘法对检测数据进行了归一化处理。相对探测效率曲线在171 ~ 2754 keV范围内的不确定度为0.1%，而在较低能量和2754 keV附近的不确定度约为0.3%。用此曲线精确测定了^<38>Cl的1643 ~ 2167 keV γ射线的相对γ射线强度为0.7496±0.0011。测量到^<27>Mg的844 keV和1014 keV γ射线的发射概率分别为0.7186±0.0008和0.2820±0.0008。通过测定^<60>Co源的崩解速率，将高精度的相对探测效率曲线转化为高精度的绝对探测效率曲线，不确定度为0.03%。利用该曲线，测量了作为多γ射线标准源的^<134>Cs和^<152>Eu的γ射线发射概率，并将其与评估值进行了比较。

Gamma-ray emission probabilities have been precisely measured by a4πβ-γ coincidence apparatus using a live-time two-dimensional data-acquisition system, and the certainties of those for ^<76>As, ^<159>Gd, ^<169>Yb, ^<182>Ta, ^<186>Re, ^<187>W and ^<188>Re have been improved by two factors or more. Furthermore, it becomes clear that the reported values for ^<76>As and ^<169>Yb are overestimated by 10% and 2%, respectively, and that those for ^<159>Gd, ^<187>W and ^<188>Re are underestimated by 5%, 20% and 3-10%, respectively.Highly precise determination of γ-ray detection efficiency curve for an HPGe detector with relative efficiency of 25% have been tried Standard sources emitting two cascade γ-rays with high probabilities were measured at 30 cm of source-detector distance under the condition of small correction for absorption and cascade summing. The sources were ^<24>Na, ^<46>Sc, ^<48>Sc, ^<60>Co, ^8Y, ^<94>Nb, ^<108>Ag and ^<111>In. The relation between energy and detection efficiency was analysed and the least-squares method using covariance matrix was applied for normalised those data. The relative detection efficiency curve was obtained with uncertainty of 0.1% between 171 and 2754 keV, whereas the uncertainty was about 0.3% in the range of lower energy and near 2754 keV.The relative γ-ray intensity of the 1643 to 2167 keV γ-rays for ^<38>Cl was very precisely determined to be 0.7496±0.0011 by using this curve. Also, the emission probabilities of the 844 and 1014 keV γ-rays for ^<27>Mg were measured to be 0.7186±0.0008 and 0.2820±0.0008, respectively. Furthermore, the highly precise relative detection efficiency curve was converted to the highly precise absolute detection efficiency curve by determining the disintegration rate of ^<60>Co source with uncertainty of 0.03%. By using this curve, γ-ray emission probabilities of ^<134>Cs and ^<152>Eu used as multi-γ ray standard source are measured and will be compared to the evaluated values.