二次电子倍增器的非线性效应研究

Research on nonlinearity effect of secondary electron multiplier

应用UTB-500铀同位素标准物质、多接收技术研究了一台热电离质谱计二次电子倍增器(SEM)的非线性效应。得出SEM的非线性效应在整个离子计数范围内都存在,非线性在离子计数率约为20000cps时,存在一个极值点,极值点的测量值与标准值之间的偏差可达3%,在极值点两边的非线性服从对数线性规律。提出了一种非线性校正的数学模型,应用该模型,可以校正热电离质谱计SEM非线性效应。

The nonlinearity of secondary electron multiplier（SEM） of a thermal ionization mass spectrometer has been researched by using UTB-500 uranium isotope reference material and multi-collecting technique.The results show that the nonlinearity effect of SEM exists in the whole ion counting range,and there is an extreme point of the nonlinearity when the ion counting rate is about 20000cps.The deviation between measured value of the extreme point and the reference value of the reference sample can be up to 3%,and the nonlinearity obeys logarithm linearity law on both sides of extreme point.A kind of mathematics model of nonlinearity calibration has been put forward.Using this model,the nonlinearity of SEM of TIMS can be calibrated.