对提高放射性同位素测量精度的研究

Research on Increasing Radioisotope Measure Precision

为评价放射性同位素测量的精度 ,对美国BeckmanLS 65 0 0ScintillationSystem的单标DPM(SLDPM)和AUTODPM两种猝灭校正方法进行了比较。结果显示 ,SLDPM的猝灭校正范围宽(校正范围由校正曲线决定 ) ,猝灭校正精度高 ,并且可以用于测试双标或三标的样品。使用AU TODPM猝灭校正方法进行测试 ,对于低能β射线3H ,在 90 <H#<1 93的范围内 ,能够达到要求的校正精度 ;当H#值在 0～ 90时 ,其校正精度不高 ;当H#值大于 1 93时 ,仪器无法进行猝灭校正 ;对于较高能量的 β射线14 C ,其猝灭校正范围与单标DPM猝灭校正方法的猝灭校正范围基本相同。但是 ,前者测试的相对误差比后者的大 ,此种猝灭校正方法只能用于测试单标样品。可见对于仪器内存猝灭校正曲线的放射性同位素 ,如3H、14 C等 ,一般使用单标DPM猝灭校正方法测试。对于35S、4 5Ca、86 Rb等仪器没有内存猝灭校正曲线的放射性同位素 ,其射线能量类似或大于14 C的均可使用AUTODPM猝灭校正方法进行测量。

To examine and judge carefully the measurement precisions of radioisotopes,two quench calibration methods in radioisotope measurement, single labeled DPM (SL DPM) and AUTO DPM were compared on Beckman LS 6500 Scintillaion System.The results show that SL DPM has wider calibration and higher precision than AUTO DPM, SL DPM can be used in measuring double-labeled or three-labeled radioisotope samples. With low-energy ( ray, i.e. 3H, when H-number is in between in 90 and 193, AUTO DPM can reach it's calibration precision; the H-number is in between 0 and 90, it's calibration precision is lower; the H-number is greater than 193, the instrument is not able of carrying through the quench calibration. With high-energy 14 C β ray, AUTO DPM measurement results are agree with SL DPM by and large, but the AUTO DPM has greater measurement error than SL DPM. Another, AUTO DPM only can be used in measuring single-labeled samples. It concludes for measuring 3H , 14 C etc, whose quench calibration function have been pre stored in the instrument, SL DPM should be considered. For 35 C , 45 Ca, 86 Rb etc, or the energy of the radiation ray is greater than 14 C, whose quench calibration functions have not been pre stored in the instrument, the measurement method should be considered to use AUTO DPM.