AMS-14C样品制备系统的研制及其性能研究

为了开展加速器质谱仪（accelerator mass spectrometry, AMS）在¹⁴C测量方面的研究，研制了可采用锌法、氢法、氢化钛法制备¹⁴C样品的装置，该制样系统以石英玻璃为主要结构材料，分为以下三个单元：系统真空维护单元、CO₂纯化单元和CO₂还原单元。为验证此装置的可靠性，进行了系列 ¹⁴C样品的制备实验，得到的石墨产率基本达到80%，同时对商业碳粉、树木的含碳量与实验过程中测量区域对应的CO₂量进行了线性拟合，结果呈现明显的线性关系。对一批标准样品和本底样品进行AMS测试，结果显示每个样品¹²C^-的引出束流均大于20 μA，系列空白样品的测量结果表明，¹⁴C/¹²C丰度比平均值为1.061×10^-15，样品制备系统稳定且在制样过程中引入的碳污染较小，符合制样要求，现代木头样品的AMS绝对测量值为（9.13±0.05)×10^-13，与预期值~9.0×10^-13相符合。上述结果表明，该系统结构紧凑，能避免相互污染，高效且便于操作，满足AMS对¹⁴C样品的测试要求。

Development of a Novel AMS-14C Sample Preparation System

A novel system for preparing ¹⁴C sample with various methods, including the zinc method, hydrogen method, and titanium hydride method, was developed for accelerator mass spectrometry (AMS) in ¹⁴C measurement. This sample preparation system consists of three units: vacuum maintenance unit, CO₂ purification unit and CO₂ reduction unit. All of the main structure is made of quartz glass. A series of ¹⁴C preparation experiment was carried out to verify the reliability of the system. The recovery rates of graphite obtained were more than 80%. The carbon content in the commercial toner and wood sample was linearly fitted to the CO₂ pressure in the measurement unit of the system. A batch of standard samples, wood samples, and dead graphite samples made by this system was performed with AMS measurement. The results showed that the beam current of ¹²C^- for each sample was greater than 20 μA. The measurement results of blank samples indicate the stability of the sample preparation system and the carbon pollution introduced during the sample preparation process was less than 5×10^-15. The absolute AMS measurement value of modern wood samples is (9.13±0.05)×10^-13, which consistents with the expected value ~9×10^-13. All the results show that the novel sample preparation system established is a compact, low-pollution, efficient, and easy to operate system, which meets the AMS requirements for ¹⁴C samples.