Ion sources for earth and planetary sciences

用于地球和行星科学的离子源

• 批准号: 3177-2006
• 负责人: Litherland, Albert
• 金额: $ 4.12万
• 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: 2008
• 资助国家: 加拿大
• 起止时间: 2008-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=388719
• 关键词: Ion; sources; earth; planetary; sciences

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.

加速器质谱（AMS）在地球和行星科学中有许多应用，特别是放射性碳定年。质谱法测量稀有的长寿命放射性原子时，由于样品量为毫克级且计数时间短，因此必须同时去除原子和分子的同量异位素。负离子消除离子源处的14N同量异位素，而串列加速器破坏分子同量异位素。然后可以获得与气候变化和考古学相关的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。许多其他长寿命同位素是天然存在的，或者是人类使用铀的结果。IsoTrace实验室正在对AMS方法进行研究，目的是将AMS推广到所有长寿命同位素。长寿命的129I被用来追踪海洋环流和追踪地下水流，用于核废物储存地点的研究，如尤卡山（美国）。从平流层探测10Be和7Be，以研究地面臭氧，使用BeF分子的阴离子，因为BF不会形成稳定的阴离子。这项由加拿大卫生部赞助的研究发现了大电子亲和力超卤阴离子对AMS的价值。BeF3阴离子是来自溅射离子源的主要离子，但BF3阴离子至多是亚稳态的，这导致了另一种可能性，用于甚至更好地测量10Be和附带的7Be。在这项工作中，发现了最小的二价阴离子LiF3。目前资助的一项提案使用四极反应电池作为串联加速之前的阴离子的广义同量异位素分离器。这一发展，与工业界合作，有望使同量异位素选择性离子源商业化，从36Cl开始，以及提供一般的超阴离子的性质的重要信息。从长远来看，消除串列加速器对某些同位素来说是可能的。