Secondary ion mass spectrometry (SIMS) has a wide range of applications in Earth Science research, thanks to its high precision and sensitivity, and its capacity in direct insitu micromeasurement. The technique is operated in ultra‐high vacuum (UHV) conditions, especially for the measurement of volatiles such as hydrogen, or the water content in nominally anhydrous minerals (NAMs). To minimize the water background and obtain accurate and precise water contents in NAMs (eg, olivine) critical parameters such as presputtering time, field aperture (FA), dynamic transfer on/off, and primary beam current intensity were investigated for a CAMECA IMS 1280‐HR system. When the chamber vacuum reaches approximately 2 × 10⁻⁹ mbar, we set the DTOS OFF, raster size to 50 μm and primary beam current to 5 nA, and used 2000 μm FA and 170‐second presputtering time. Consequently, an approximately 1.2 ppmw water background and 3.6 ppmw limit of detection (LOD) were yielded, from analyzing the San Carlos olivine. Meanwhile, the water content and homogeneity of a range of olivine minerals were characterized for potential use as reference materials for SIMS water content measurement. Olivine water content calibration curve was also established by comparing the Fourier transform infrared (FTIR) results with the SIMS‐measured ¹⁶O¹H⁻/¹⁶O⁻ ratios. Accuracy and precision of water content measurement were estimated to be better than approximately 10% in this study.

中文翻译：

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橄榄石水分测量中SIMS分析参数的优化

二次离子质谱（SIMS）的高精度和高灵敏度以及直接进行原位显微测量的能力，在地球科学研究中具有广泛的应用。该技术在超高真空（UHV）条件下运行，尤其是用于测量挥发性物质，例如氢气或名义上无水矿物（NAM）中的水分。为了最小化水的背景并在NAM（例如橄榄石）中获得准确准确的水含量，对CAMECA IMS 1280的关键参数（例如预溅射时间，场孔径（FA），动态转移开/关和一次电子束电流强度）进行了研究。 ‐HR系统。当腔室真空度达到约2×10 ^-9时毫巴，我们将DTOS设置为OFF，将光栅尺寸设置为50μm，并将主束电流设置为5 nA，并使用2000μmFA和170秒的预溅射时间。因此，通过分析San Carlos橄榄石，可得到约1.2 ppmw的水本底和3.6 ppmw的检出限（LOD）。同时，表征了一系列橄榄石矿物的水分含量和均质性，可作为SIMS水分含量测量的参考材料。橄榄石含水量校准曲线还通过比较所述傅里叶变换红外（FTIR）的结果与所建立的SIMS测量的¹⁶ ö ¹ ħ ^- / ¹⁶ ö ^-比率。在这项研究中，水含量测量的准确性和精确度估计要好于大约10％。