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本文介绍液体闪烁计数法绝对测量~3H、~(14)C活度的装置,测量结果和比对情况。甄别电压外推到零时的计数率随光电倍增管阳极电流而改变,当阳极电流的倒数趋于零时,计数率趋于被测源的活度。放置~3H、~(14)C溶液和闪烁体的瓶子是半球形的石英瓶或低钾玻璃瓶,底部直接耦合到光电倍增管的阴极上。在半球面的外部,涂TiO_2作为反射层。测量~3H的效率达86％,~(14)C的效率达91％。测量~3H、~(14)C活度的合成不确定度分别为0.80％和0.30％。
This article describes the device for the absolute measurement of ~ 3H, ~ (14) C activity by liquid scintillation counting, measurement results and comparison. When the discrimination voltage is extrapolated to zero, the count rate will change with the PMT anode current. When the anode current reciprocals to zero, the counting rate tends to be measured source activity. Bottles of ~ 3H, ~ (14) C solution and scintillator were either hemispherical quartz or low-pot glass bottles with the bottom directly coupled to the cathode of a photomultiplier tube. Outside the hemispherical surface, TiO 2 is used as a reflection layer. The efficiency of measuring ~ 3H was 86%, and the efficiency of ~ (14) C was 91%. The synthetic uncertainties of measuring ~ 3H, ~ (14) C activity were 0.80% and 0.30%, respectively.