Enhanced anion production and isobar separation for accelerator mass spectrometry

加速器质谱（AMS）是从核物理学发展而来的一门科学，在科学领域有着广泛的应用.质谱法测量稀有长寿命放射性原子的亚毫克样品尺寸和短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同量异位素。对于14 C，使用负离子消除了离子源处的14 N等压线，串联加速器破坏了分子等压线，从而促进了与气候变化、天体物理学、医学和考古学相关的14 C测量。由于宇宙射线的相互作用或人类对铀的使用，环境中存在许多其他长寿命同位素。例如，10 Be用于表面暴露年代测定，而长寿命的129 I用于追踪海洋环流和追踪核废物储存场地研究的地下水流。目前正在对AMS方法进行研究，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进行完全的原子同量异位素分离。超卤阴离子在离子源上增强同量异位素的研究已证明是卓有成效的。在早期的工作中，发现了超离子导体PbF 2有助于产生许多超氟阴离子如AlF 4-、SiF 5-、PF 6-等的功效。NSERC资助的I2 I提案，使用RF四极化学反应池在串联加速之前进行阴离子的广义同量异位素分离，已经成功进行了初步测试。这导致了在低水平下检测36 Cl和41 Ca，而不需要大型加速器。与工业界合作，这一发展有望使同量异位素选择附近的离子源商业化，开始与36氯，以及提供许多有用的信息的性质的超级阴离子，二价阴离子和离子气体化学反应一般。

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.