International Research Fellowship Program: Search for Isotopes from Recent Nearby Supernova with Nearby Accelerator Mass

[502034]列文国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持乔纳森·莱文博士为期三个月的研究奖学金。Jorge O. Fernandez-Niello和Andres Arazi就职于阿根廷布宜诺斯艾利斯国家能源原子物理委员会TANDAR实验室。大多数到达地球的陨石在被侵蚀和风化破坏之前最多能存活几千年。特定陨石的所谓“地球年龄”，或者陨石坠落地球的时间，可以通过测量放射性同位素的丰度来计算。碳-14被广泛用于这一目的。然而，一些陨石足够古老，没有可检测到的碳-14残留。这些罕见的陨石对于研究不同类型的陨石在过去几万年里的坠落率是如何变化的问题，以及对发现它们的缓慢侵蚀地区的地质研究来说，都是特别有趣的。研究人员正试图通过丰富的放射性镍-59（半衰期为76000年）来确定这些古老陨石的地球年龄。他们通过加速器质谱法寻找镍-59，这使他们能够检测到镍-59丰度低于样品中总镍禀量的万亿分之一。他们正在努力通过改进化学分离、质量分辨率和离子检测技术来进一步提高灵敏度。镍-59为测定陨石的年代提供了最大的希望，这些陨石来自保存非常完好的地质环境，比如南极洲，由于气候干燥，那里的陨石被侵蚀的速度比其他地方要慢得多。

0502034LevineThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a three-month research fellowship by Dr. Jonathan Levine to work with Drs. Jorge O. Fernandez-Niello and Andres Arazi at Laboratorio TANDAR, Comision Nacional de Energia Atomica Phycics in Buenos Aires, Argentina.Most meteorites that reach the Earth survive for a few thousands years, at most, before they are destroyed by erosion and weathering. The so-called "terrestrial ages" of particular meteorites, or the duration of time since a meteorite has fallen to Earth, can be calculated from the measured abundance of radioactive isotopes. Carbon-14 is used extensively for this purpose. However, some meteorites are old enough that no detectable carbon-14 remains. These rare meteorites are especially interesting for questions about how the fall-rate of different types of meteorites has changed over the last several tens of thousands of years, as well as for geological studies of the slowly-eroding regions where they are found. The investigators are attempting to determine the terrestrial ages of such old meteorites from the abundance of radioactive nickel-59 (half-life 76,000 years). They search for nickel-59 by accelerator mass spectrometry, which allows them to detect nickel-59 abundances lower than one part per trillion of the total nickel endowment of a specimen. They are working to further improve the sensitivity, by improving chemical separation, mass resolution, and ionic detection techniques. Nickel-59 offers greatest promise for dating meteorites collected from geological settings of extraordinary preservation, such as Antarctica, where meteorites are eroded much more slowly than elsewhere because of the dry climate.