Advanced Instrumentation for Research in Accelerator Mass Spectrometry

加速器质谱法（AMS）是一种用于测量微量样品中稀有原子或同位素浓度的技术，灵敏度高达1 / 1015（十亿分之一）。这种测量通常限于容易产生负离子（阴离子）的元素，以及不存在具有相同质量的其他元素（等压线）的阴离子的元素，例如14C和129I。如果原子等压线确实存在，测量需要使用更大的加速器（bbb5毫伏）和繁琐的样品制备化学。在IsoTrace实验室（多伦多）关闭前不久，它开始了两项创新，为将AMS扩展到元素周期表的更大部分提供了基础。这些是：(i)使用氟分子阴离子来增加AMS所需阴离子的生产；（ii）在冷却和反应细胞中使用射频四极离子导流器，以非常低的能量消除原子和分子等压线——为此开发了一个原型系统，即阴离子等压线分离器（ISA）并获得专利。***这项研究的主要和长期目标是更全面地了解使该设备工作的物理（和一些化学）过程，但这似乎限制了其进一步发展。这种理解将通过制定新的程序和组件来检验，如果成功，这些程序和组件将成为未来AMS系统的一部分。渥太华大学的a . E. Lalonde AMS实验室的调试，以及IsoTrace最近开发的设备的结合，提供了一个独特的机会来加深这种理解，开发基于这些知识的新技术，并探索它们所能实现的许多新应用。近期研究计划将包括：***a)研究ISA早期工作中观察到的新现象。这些包括控制离子的能量和位置的必要性，寻找具有电子可以共振转移的状态的反应气体，以及测定分析物、等压板或反应气体分子的结构。***b)研究氟化物阴离子形成过程。最近在Lalonde实验室发现了使用高电流离子源产生更大分子阴离子束的新方法，但这些过程尚未被理解。***c)重新启动气体离子源研究，因IsoTrace关闭而推迟。这是由于许多科学家需要分析化合物特定（因此更小）的14C样品，并最终将这种能力扩展到氚和129I测量，以及与使用AMS的研究人员继续合作，以支持他们在不同领域的工作，例如追踪污染物途径，确定地质过程的年表，实现核法医调查，测试新药物和监测人类健康方面。

Accelerator mass spectrometry (AMS) is a technology used to measure concentrations of rare atoms or isotopes in milligram samples with sensitivities as high as 1 part in 1015 (thousand million million). Such measurements are generally limited to elements which readily make negative ions (anions) and for which anions of other elements with the same mass (isobars) do not exist, e.g. 14C and 129I. If atomic isobars do exist, measurements require the use of larger accelerators (>5 MV) and tedious sample preparation chemistry. Two innovations begun at the IsoTrace Laboratory (Toronto), shortly before it was closed, provided the groundwork needed for the extension of AMS to a much larger fraction of the periodic table. These are: (i) the use of fluoride molecular anions to increase the production of the anions required for AMS and (ii) the use of radio-frequency quadrupole ion guides in cooling and reaction cells to eliminate both atomic and molecular isobars at very low energies - for which a prototype system, the Isobar Separator for Anion (ISA) has been developed and patented.***The primary and long-term goal of this research is to more fully understand the physical (and some chemical) processes which make this equipment work, but which seem to limit its further development. This understanding will be tested by formulating new procedures and components, which, when successful, will become part of future AMS systems. The commissioning of the A. E. Lalonde AMS Laboratory at the University of Ottawa, and the incorporation of recently developed equipment from IsoTrace, provide a unique opportunity to deepen that understanding, to develop new techniques based on this knowledge and to explore the many new applications which they enable. The near-term research program will include:***a) investigating new phenomena observed in earlier work on the ISA. These include the necessity to control the energy and position of the ions, the search for reaction gases with states to which electrons can be resonantly transferred and the determination of the structure of the analyte, isobar or reaction gas molecules. ***b) investigating processes in the formation of fluoride anions. New methods for generating larger molecular anion beams were recently discovered using the high current ion sources at the Lalonde Lab, but these processes are not yet understood. ***c) re-starting the gas ion source research, delayed by the IsoTrace closing. This is motivated by the need of many scientists to analyze compound-specific (hence smaller) 14C samples with the eventual extension of this capability to tritium and 129I measurements, and ***d) continuing collaboration with researchers using AMS to support their work in diverse fields such as tracing pollutant pathways, determining chronologies for geological processes, enabling nuclear forensic investigations, testing new pharmaceuticals and monitoring aspects of human health.