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: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=361186
• 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.

加速器质谱法（AMS）在地球和行星科学特别是放射性碳测年中有许多应用。质谱法对罕见的长寿命放射性原子的样品大小为毫克，计数时间短，因此必须去除原子和分子等压线。负离子消除离子源处的14N等压线，串联加速器破坏分子等压线。这样就可以获得与气候变化和考古有关的14C年代。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级闪烁计数器有关。许多其他长寿命同位素是自然存在的，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用于追踪海洋环流和追踪核废料储存地点研究的地下水流，如尤卡山（美国）。从平流层检测10Be和7Be，研究地面臭氧，利用分子BeF的阴离子，因为BF不形成稳定的阴离子。这项由加拿大卫生部赞助的研究发现了大电子亲和超卤化物阴离子对AMS的价值。BF3阴离子是溅射离子源的优势离子，但BF3阴离子最多是亚稳态的，这导致了另一种更好地测量10Be和顺便测量7Be的可能性。在这项工作中，最小的离子LiF3被发现。目前资助的一项建议是，在串联加速之前，使用四极反应电池作为阴离子的广义等压分离器。与工业界合作的这一发展，有望使从36Cl开始的等压选择性离子源商业化，并提供关于超阴离子一般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可能的。