Upgrade of Noble Gas Mass Spectrometer (VG5440) for Use in the Earth and Environmental Sciences

该合同将允许升级稀有气体质谱仪（VG5440）的电子单元，该质谱仪现已运行超过18年。这次升级将恢复并大大提高机器的测量能力，以便我们可以在氖和氮同位素地球化学领域开展新的研究。我们计划或正在进行当代Ne和N2研究的4个领域的研究：(1)利用宇宙成因的21Ne进行地表暴露测年。我们计划改进鉴定天然材料中宇宙射线产生的21Ne的方法，特别是解决基于21Ne， 10Be和26Al核素的年龄差异。(2)洋岛玄武岩（OIB）氖同位素系统。我们计划在不同类型的OIB中寻找Ne同位素的非均质性。我们试图通过针对冰岛（和其他OIB）样本进一步评估He和Ne之间的关系，这些样本在全球范围内具有最高的3He/4He值。(3)利用Ne同位素进行地下水补给研究。Neon有潜力通过研究在某些含水层系统中发现的“过量空气”成分来确定地下水补给的机制。(4)确定“富集”地幔的氮同位素系统。我们以冰岛和邻近的雷克雅内斯脊为主要地点，以深入了解陆地地幔的特征n同位素变化。此外，该提案将更新一个专门的氖同位素设施，其主要作用是培养研究生和博士后访客。迄今为止，已有相当数量的知名研究人员在Scripps/UCSD实验室接受了稀有气体地球化学方面的培训，这笔资金将使这一传统得以延续。

This award will permit the upgrade of the electronics units of a noble gas mass spectrometer (VG5440) which has now been in operation for over 18 years. The upgrade will restore and significantly enhance the measurement capabilities of the machine so that we can initiate new studies in the field of neon and nitrogen isotope geochemistry. We plan to or are pursuing studies in 4 areas of contemporary Ne and N2 research: (1) Surface exposure dating using cosmogenic 21Ne. We plan improvements in the methodology of identifying cosmic-ray-produced 21Ne in natural materials, specifically to resolve discrepancies between ages based on 21Ne, 10Be and 26Al nuclides. (2) Neon isotope systematics of ocean island basalts (OIB). We plan to search for Ne isotopic heterogeneity in various classes of OIB. We seek to further evaluate the relationship between He and Ne by targeting Icelandic (and other OIB) samples which have amongst the highest 3He/4He values worldwide. (3) Groundwater recharge studies utilizing Ne isotopes. Neon has the potential to identify mechanisms of groundwater recharge through studies of the 'excess air' component identified in some aquifer systems. (4) Defining the nitrogen isotope systematics of the 'enriched' mantle. We have targeted Iceland and the adjacent Reykjanes Ridge as prime localities to gain insight into the characteristic N-isotope variations of the terrestrial mantle. Furthermore, this proposal will update a dedicated neon isotope facility whose primary role is training of graduate students and post-doctoral visitors. To date, a significant number of established researchers have received their training in noble gas geochemistry using the Scripps/UCSD laboratories and this funding will allow this tradition to continue.