MRI: Acquisition of a Multi-collection Detector System for the Cameca IMS 1280 in the Northeast National Ion Microprobe Facility

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This Major Research Instrumentation (MRI) Program award provides funds to upgrade the Cameca IMS 1280 ion microprobe operated by the Northeast National Ion Microprobe Facility (NENIMF) with a multi-collection detector. Secondary ion mass spectrometry (SIMS) is a powerful micro-analytical technique for determining the elemental and isotopic compositions of solid materials that has broad applications to earth, ocean, and planetary sciences. The NENIMF has operated as a highly productive, NSF-supported National Facility for twenty-six years and is equipped with instrumentation and personnel that are ideally suited to help the geoscience community take full advantage of multi-collector SIMS. An IMS 1280 upgraded with multi-collection capability would complete the NENIMF as a cutting-edge SIMS facility serving the US geoscience community for a fraction of the cost of purchasing a new Cameca IMS 1300-HR3 (~$7 million). The mono-collection NENIMF IMS 1280 has established an important niche in the geoscience community as a major source of high-quality data on volatile element concentrations in silicate glasses, glass inclusions, and nominally anhydrous minerals. The upgrade to multi-collection will be leveraged by combining this existing expertise with the capability to analyze light stable isotopes on the same spots and, thereby, allow us to provide exciting and innovative new SIMS applications for users of the facility. The proposed upgrade would greatly enhance studies of pre-eruptive magmatic volatiles, which represent an important control on volcano explosivity, as well as volatiles (especially sulfur) in the solid Earth, cosmochemistry, oxygen isotope thermometry, biogenic carbonates, and biogeochemistry.The Cameca IMS 1280 is a double focusing mass spectrometer with a large radius magnetic sector, and ion optics optimized to attain a mass resolving power of 6000 without significant loss of secondary ion intensity. Starting in 1998, an increasing number of IMS 1270/1280 ion microprobes have been equipped with the capability to measure up to five isotopes simultaneously (multi-collection). Multi-collection has a number of significant advantages over mono-collection. First, it increases the efficiency of data collection and – thereby – minimizes the effect of instrumental drift. For example, the time required to determine the isotopic composition of S in sulfides or O in silicates is decreased from approximately 12 minutes per spot using mono-collection to only 4 minutes per spot by multi-collection. This leads to significant improvements in accuracy and reproducibility because instrumental drift can be corrected for through a much higher frequency of standard analyses between samples. Second, the ability to measure multiple isotopes simultaneously leads to a significant increase in data quality by minimizing the effects of instability and drift of the primary ion beam. For example, the 32S/34S measurements on sulfide standards on the NENIMF mono-collection system have a typical precision of 0.07-0.12 ‰ 2RSE (relative standard error) and a spot to spot reproducibility (accuracy) of ~0.6 ‰ 2RSD (relative standard deviation). Multi-collector analysis on the same standards have a precision of 0.02-0.03 ‰ 2RSE and accuracy 0.1 ‰ 2RSD. Third – and most importantly – multi-collection allows for high-precision in situ analysis of stable isotopes of light elements such as H, C, O, S, and Cl.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.