Instrument: The NanoSIMS-HR, like its predecessors the NanoSIMS 50 and 50L, is a scanning ion microprobe coupled to a double-focusing mass spectrometer with a Mattauch-Herzog design, which enables multicollection of secondary ions over a large relative mass range (~22x for the 50L) . The primary ions are accelerated toward the sample surface and steered and focused to the desired spot size by a suite of Einzel lenses and deflectors. To optimize focusing, the instrument is designed so that the primary and secondary ions travel in opposite directions through a single "coaxial" lens stack near the sample. As a result, the primary ion source and the sample surface must be at the same potential and opposite polarity. Normal operation is with the source and sample at |8000V|, resulting in a primary ion impact energy of 16 keV. The NanoSIMS-HR multicollection system has seven detectors, six of which are on movable trolleys to enable mass selection. Electron multiplier (EM) ion detectors in pulse counting mode are used to enable imaging; these can be swapped for Faraday cups (FC) for high-current, higherprecision isotope measurements. Relative to its predecessor instruments, the NanoSIMS-HR includes several key upgrades: