流气式低本底α/β测量仪的串道特征及干扰修正

Crosstalk interference and correction methods for low background gas-flow proportional counter

研究了一系列α、β金属平面源、粉末源及薄层样法自制面源在流气式低本底α/β测量仪上的串道现象。结果显示:^(90)Sr-^(90)Y金属面源以及 ^(14)C,^(137)Cs,^(90)Sr-^(90)Y, ^(40)K粉末源β对α通道的串道比均在0.1%以下,基本可以忽略不计;α金属平面源串道比大小规律表现为 ^(210)Po<^(209)Po<^(239)Pu<^(239)Pu-^(241)Am混合源<241Am,范围为3.49%~25.4%,发射不同能量粒子的α金属源的串道比差异较大。由于衰变过程产生的内转换电子、俄歇电子以及X射线等在β道产生响应,241Am源的串道比明显高于其他源,241Am粉末源的串道比随单位面积质量厚度增加而增大。α粒子对β通道的串道现象较明显,并与样品制源方式有关,主要是不同制源方式造成的自吸收差异导致的,总体有α粉末源串道比>薄层样法自制α面源>α金属平面源,测量时应重点考虑α粒子对β放射性的串道干扰。通过210Po加标样及牡蛎样品经放化分析制成的电镀源验证,对待测样品源进行一定厚度的铝箔或纸片覆盖,可以有效的减小α粒子对β通道的串道干扰;也可以直接利用串道比对测量计数进行修正,此时需要考虑待测样品源和串道比刻度源的一致性,否则会导致修正结果的偏差较大。

The crosstalk phenomenon and its influence in the determination of grossαandβradioactivity when using a low background gas-flow proportional counter as a measuring instrument was examined in this paper.The crosstalk ratio betweenαandβchannel was measured by using a series ofα,βmetal planar sources,powder sources,and thin-layer surface sources.Theβ-to-αcrosstalk ratio of ^(90)Sr-^(90)Y metal planar sources and powder sources containing ^(14)C,^(137)Cs,^(90)Sr-^(90)Y,or ^(40)K is less than 0.1%,which can be negligible.The crosstalk ratios ofαmetal planar source in ascending order are ^(210)Po,^(209)Po,^(239)Pu,^(239)Pu-^(241)Am mixed source,and 241Am,which range from 3.49%to 25.4%.The crosstalk ratio of 241Am is significantly higher than those of other sources.Furthermore,241Am powder sources'crosstalk ratio increases with mass thickness.The crosstalk ofαparticles toβchannel is obvious and related to the sample source preparation method.This is mainly due to the difference in self-absorption due to different source preparation methods.Overall,the crosstalk ratio ofαpowder sources is larger than thin-layer surface sources and metal planar sources.The interference ofα-to-βcrosstalk should be considered.By covering the sample sources with aluminum foil or paper with a certain thickness,the crosstalk interference ofα-to-βcan be reduced effectively.Additionally,it is an effective way to directly correct the count rate by the crosstalk ratio.In this case,it is necessary to consider the consistency of the sample source to be measured and the crosstalk ratio scale source,as any discrepancies can lead to a significant deviation in the corrected result.