MAT261质谱计二次电子倍增器歧视效应研究和计数法建立

摘要

Mass discrimination effect and ions intensity-dependent discrimination effect of secondary electron multiplier (SEM) in analog mode for MAT261 thermal ionization mass spectrometry (TIMS) were carried out. Mass discrimination factor were determined accurately and the measurement conditions under which ions intensity-dependent discrimination effect could be ignored were obtained. Moreover, the count mode of SEM was established for accurate measurement of weak signal. Comparison with the two modes, which were finished using standard solution of plutonium. The results from analog mode corrected by mass discrimination effect and directly from count mode of SEM respectively agree well with the nominal value. It means that accurate analysis of weak signal can be achieved using the established count mode of SEM.%热表面电离质谱计(TIMS)MAT261在采用二次电子倍增器(SEM)接收时,SEM积分模拟模式的测量存在质量歧视效应和强度歧视效应.本研究测量了其质量歧视校正因子,建立了强度歧视效应基本可以忽略的测量方法.为实现弱信号的准确测量,建立SEM离子计数测量模式.基于SEM离子计数测量技术,应用钚标样比较SEM积分模拟模式测量和离子计数模式测量的结果.在控制离子流强度的条件下,两种方法的测量结果与标样标称值在不确定度范围内符合.