AMS测量^(32)Si的ΔE-Q3D方法

The ΔE-Q3D method for AMS measurement of ^(32)Si

32Si(~140a)是Si的唯一长寿命放射性核素,在100-1000a时间尺度的同位素地质定年和硅的全球生物地球化学循环研究中有不可替代的重要地位。加速器质谱技术(AMS)的灵敏度高、样品用量少、测量时间短,是测量32Si的最合适方法。本实验室正在着力建立32Si的AMS测量法。在游泳池堆中辐照31P和30Si生产32Si;通过实验确定了样品的化学形式、离子源导电介质种类及其比例和离子源引出形式;建立了从辐照样品提取32Si和稀释高含量样品的化学流程。经多次实验条件摸索和改进,成功测得了含量为10-13水平的样品中的32Si计数,灵敏度好于1.5×10-14,成功建立了AMS高灵敏测量32Si的ΔE-Q3D方法。

^ 32Si, the only long-life （-140 a） radioisotope of silicon, plays a unique role in geochronometry in the range of 100-1000 years, and in research of the global biogeochemical silica cycle. Because of its ultra high sensitivity, minute sample amount and short measurement time, the accelerator mass spectrometry （AMS） is the most proper method for detecting ^32Si. China Institute of Atomic Energy has been making efforts in establishing the ultra-sensitive method of ^32Si determination via AMS. ^31p and ^30Si targets are irradiated in a swimming pool reactor to produce ^32Si. Chemical procedures to extract the ^32Si from the irradiated targets have been decided, along with electric conductor materials and the mixing ratio, the negative ion formation method, and processes to dilute the solutions to form high ^32Si abundance samples. After several tests and improvements of the experimental conditionals, we were able to measure the sample at the abundance of 10^- 13 in a sensitivity of better than 1.5× 10^-14. In this paper, we report our progresses in establishing the AMS-based △E-Q3D method for ^32Si determination.