Ion sources for earth and planetary sciences

加速器质谱仪(AMS)在地球和行星科学中有着广泛的应用，尤其是在放射性碳测年方面。稀有的长寿命放射性原子的毫克样品大小和短的质谱学计数时间要求必须同时去除原子和分子的同素异位素。负离子在离子源处消除了14N等压素，串列加速器破坏了分子等压素。然后就可以获得与气候变化和考古有关的14C日期。天然碳氢化合物中14C的测量与建造用于太阳中微子和暗物质研究的千吨闪烁计数器有关。许多其他长寿的同位素是自然存在的，或者是人类使用铀的结果。同位素示踪实验室正在对AMS方法进行研究，目的是将AMS推广到所有长寿命的同位素。长寿命的129I被用于追踪海洋环流和追踪地下水流，用于核废料储存地点的研究，例如美国的尤卡山。为了研究地面臭氧，从平流层探测10Be和7Be，使用BEF分子的阴离子，因为BF不形成稳定的阴离子。这项研究由加拿大卫生部赞助，发现了大电子亲和力的超卤化物阴离子对AMS的价值。BeF3阴离子是来自溅射离子源的主要离子，但BF3阴离子至多是亚稳定的，这导致了另一种更好地测量10Be和7Be的可能性。在这项工作中，发现了最小的双阴离子LiF3。目前资助的一项提案使用四极反应池在串联加速之前对阴离子进行广义等压素分离器。这一发展，与工业界合作，有望使从36Cl开始的等压素选择性离子源商业化，并提供有关超阴离子总体性质的许多重要信息。从长远来看，消除串列加速器对某些同位素来说是有可能的。

Accelerator Mass Spectrometry (AMS) has many applications in the Earth and Planetary Sciences especially radiocarbon dating. The milligram sample sizes and the short counting time of the rare long-lived radioactive atoms by mass spectrometry require that both atomic and molecular isobars must be removed. Negative ions eliminate the 14N isobar at the ion source and the tandem accelerator destroys the molecular isobars. 14C dates relevant to climate change and archaeology can then be obtained. The measurement of 14C in natural hydrocarbons is relevant to the construction of kiloton scintillation counters for solar neutrino and dark matter studies. Many other long-lived isotopes are present naturally or as a result of the human use of uranium. Research into the AMS method is being carried out at the IsoTrace Laboratory with the aim of generalizing AMS to all long-lived isotopes. Long-lived 129I is used to trace oceanic circulation and to trace underground water flow for Nuclear Waste Storage sites studies, such as Yucca Mountain (USA). The detection of 10Be and 7Be from the stratosphere, to study ground level ozone, uses the anion of the molecule BeF as BF does not form stable anions. This research, sponsored by Health Canada, led to the discovery of the value of the large electron affinity super-halide anions for AMS. The BeF3 anion is a dominant ion from a sputter ion source but the BF3 anion is at most metastable leading to another possibility for even better measurements of 10Be and incidentally 7Be. During this work the smallest dianion, LiF3, was discovered. A currently funded proposal uses quadrupole reaction cells for a generalised isobar separator for anions prior to tandem acceleration. This development, in collaboration with industry, promises to make isobar selective ion sources commercially available, starting with 36Cl, as well as provide much important information on the properties of the super-anions in general. In the long run the elimination of the tandem accelerator is a possibility for some isotopes.