Upgrade of a Helium Isotope Mass Spectrometer

0549533Kurz这笔赠款支持升级伍兹霍尔海洋研究所(WHOI)现有的专门用于岩石和矿物测量的氦同位素质谱仪。目前的质谱计是全自动的，自20世纪80年代初以来一直持续运行，但有许多过时的部件。升级的内容包括：1)用一台运行Windows XP的现代奔腾电脑替换一台PDP-11计算机控制系统；2)升级一台低温系统；更换氦气压缩机和两个冷头中的一个；3)升级真空系统；3)安装新的涡轮分子泵和特高压阀；4)安装新的离子光学元件、通道加速器探测器和开发新的离子源；以及5)购置一台新的四极质谱仪，在进入惰性气体质谱仪的磁区之前对样品气体进行预测量。所要求的升级预计将使系统的探测极限降低大约10倍(至~1000个原子3He)。这将通过安装离子计数检测电子器件和能量过滤器(在电子倍增器上)、升级离子源和升级超高真空组件来实现。升级后的质谱仪将促进基于对地幔矿物中3He/4He比率的高精度、低检测下限分析的地幔动力学/脱气研究，包括对从夏威夷科学钻探项目回收的材料的分析，该项目只有少量样品可供研究。宇宙中的3He测量还将被用来确定地球表面物质的暴露年龄，以支持古气候研究(例如，冰川冰川测年)和景观演变研究。升级后的He专用惰性气体质谱仪是WHOI成本中心(WHOI同位素地球化学设施)的一部分，将向WHOI科学家和麻省理工学院-WHOI联合博士项目的学生以及更广泛的美国科学界提供。将开发一个新的网站，宣传互联网治理论坛现有的分析能力。

0549533KurzThis grant supports upgrade of an existing helium isotope mass spectrometer dedicated to measurements of rocks and minerals at Woods Hole Oceanographic Institution (WHOI). The current mass spectrometer is fully automated and has been operating continuously since the early 1980s but has many antiquated components. Components of the upgrade would include: 1) replacement of a PDP-11 computer control system with a modern Pentium PC running Windows XP; 2) upgrade of the cryogenic system replacement of helium compressor and one of two cold heads; 3) upgrade of the vacuum system new turbomolecular pumps and UHV valves; 4) installation of new ion optics, a Channeltron detector and development of a new ion source; and 5) acquisition of a new quadrupole mass spectrometer to premeasure sample gases prior to inlet into the magnetic sector of the noble gas mass spectrometer. The requested upgrade is expected to lower the detection limit of the system by roughly a factor 10 (to ~ 1000 atoms 3He). This would be accomplished by installing ion counting detection electronics and an energy filter (on the electron multiplier), by upgrading the ion source, and by upgrading the ultra high vacuum components. The upgraded mass spectrometer would facilitate studies of mantle dynamics/degassing based on high precision, low detection limit analyses of 3He/4He ratios in mantle minerals, including analysis of materials recovered from the Hawaiian Scientific Drilling Project, where only small samples are available for study. Cosmogenic 3He measurements will also be used to determine the exposure age of materials at the earth's surface to support paleoclimate studies (e.g, dating of glacial moraines) and research on landscape evolution. The upgraded He dedicated noble gas mass spectrometer is part of a WHOI cost center (the WHOI Isotope Geochemistry Facility) and will be available to WHOI scientists and students in ther MIT-WHOI joint Ph.D. program, and also to the broader U.S. science community. A new web site will be developed to advertise the analytical capabilities available in the IGF.