Cameca IMS 1280-HR
The IMS 1280-HR is a second-generation large magnet-radius SIMS instrument capable of analyzing positive or negative secondary ions at high sensitivity and spatial resolution. Ion sources are a duoplasmatron (producing positive and negative oxygen ions) and a Cs2CO3 source (thermally generating positive Cs ions). A normal-incidence electron gun is available for charge compensation during negative ion analysis of insulators. Samples and mounting materials cannot exceed 25.4 mm in diameter and 5 mm in height, and they must be ultrahigh vacuum compatible, have flat surfaces, and for insulators be coated with a conductive layer (mostly Au or C). New high precision sample holders permit reliable analysis within 8 mm from the center of the mount; targeting outside this “bulls-eye” area is not recommended. An eight sample airlock system allows for rapid change of samples. The sample surface is imaged by a reflected light microscope. Automated analysis is possible at stage position reproducibility of 2 µm. The large magnet radius (585 mm) enables high transmission with insignificant loss up to a mass resolution m/Δm of 6,000, and high mass resolution (m/Δm up to 30,000) over a total mass range of ca. 300 amu (i.e., from H to UO2). Multicollection using five moveable trolleys equipped with interchangeable electron multipliers (EM) and Faraday cups (FC) is possible from Li to U. Analysis spots are typically ~20 µm (Köhler mode for routine geochronology) and ~10 µm (stable isotope analysis using a focused Cs+ beam); smaller ion beams are tunable for special applications such as scanning ion imaging. The IMS 1280-HR also acts as an ion microscope which can image secondary ions emission from the sample surface by means of a channel plate, and a resistive anode encoder. Like its smaller (e.g., IMS 3F analogs, the IMS 1280-HR is also capable of depth profiling at 10’s of nm resolution. Routine geochronologic applications have a sensitivity (useful yield = ions detected over atoms removed) of 1% for Pb+ and reproducibility for Pb/U of 1-2% (1 standard deviation) that is equivalent to SHRIMP instrumentation. Uncertainties for routine stable isotope (e.g, C, O, S) analysis using FC detectors are ~0.2‰ (~0.6 ‰ with EMs).