Enhanced anion production and isobar separation for accelerator mass spectrometry

增强加速器质谱分析中的阴离子产生和等量异位素分离

• 批准号: 3177-2010
• 负责人: Litherland, Albert
• 金额: $ 2.33万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=520551
• 关键词: Enhanced; anion; production; isobar; separation

Accelerator Mass Spectrometry (AMS), which developed from nuclear physics, has many applications in the Sciences. The sub-milligram samples sizes and the short counting time for the measurement of rare long-lived radioactive atoms by mass spectrometry require that stable atomic isobars must be removed from the high currents needed from the ion source. For 14C, the use of negative ions eliminates the 14N isobar at the ion source and a tandem accelerator destroys the molecular isobars, thereby facilitating 14C measurements relevant to climate change, astrophysics, medicine and archaeology. As a result of cosmic ray interactions or the human use of uranium many other long-lived isotopes are present in the environment. Examples are, 10Be, used for surface exposure dating, and long-lived 129I, used to trace oceanic circulation and to trace underground water flow for Nuclear Waste Storage site studies. Research into the AMS method is being carried out with the aim of improving and extending AMS to all long-lived isotopes, as only three can exploit negative ion instability for complete atomic isobar separation. The study of isobar enhancement at the ion source by means of superhalogen anions has proved very fruitful. During earlier work the efficacy of the super-ionic conductor PbF2 for helping to generate many of the super fluoride anions such as AlF4-, SiF5-, PF6- etc was discovered. An NSERC funded I2I proposal, which uses RF quadrupole chemical reaction cells for the generalised isobar separation of anions prior to tandem acceleration, has had successful initial tests. This has led to the detection of 36Cl and 41Ca at low levels without the need for large accelerators. In collaboration with industry, this development promises to make isobar selection near the ion source commercially available, starting with 36Cl, as well as providing much useful information on the properties of the super-anions, dianions and ion-gas chemical reactions in general.

加速器质谱法（AMS）是从核物理学发展而来的，在科学领域有许多应用。通过质谱法测量稀有长寿命放射性原子的亚毫克级样品大小和较短的计数时间要求必须从离子源所需的高电流中去除稳定的原子等压线。对于 14C，负离子的使用消除了离子源处的 14N 等压线，而串联加速器则破坏了分子等压线，从而促进了与气候变化、天体物理学、医学和考古学相关的 14C 测量。由于宇宙射线相互作用或人类使用铀，环境中存在许多其他长寿命同位素。例如，10Be 用于表面暴露测年，长寿命 129I 用于追踪海洋环流和追踪地下水流以进行核废料储存场地研究。对 AMS 方法的研究正在进行中，目的是改进 AMS 并将其扩展到所有长寿命同位素，因为只有三种同位素可以利用负离子不稳定性来实现完整的原子同位素分离。通过超卤素阴离子增强离子源等压线的研究已证明非常富有成效。在早期的工作中，发现了超离子导体 PbF2 有助于产生许多超氟化物阴离子（如 AlF4-、SiF5-、PF6- 等）的功效。 NSERC 资助的一项 I2I 提案已成功进行了初步测试，该提案使用射频四极化学反应池在串联加速之前对阴离子进行广义等量异位素分离。这使得无需大型加速器即可检测到低浓度的 36Cl 和 41Ca。通过与工业界的合作，这一进展有望使离子源附近的等量异位素选择商业化，从 36Cl 开始，并提供有关超阴离子、双阴离子和离子-气体化学反应的一般性质的许多有用信息。