Emulation of the curiosity rover alpha particle X-ray spectrometer with accelerator-based PIXE: II

Mono-mineral and ultramafic geochemical reference materials (GRMs) were analyzed using a 2.5 MeV broad-beam proton-induced X-ray emission (PIXE) system designed to emulate the PIXE branch of the Mars Science Laboratory alpha-particle X-ray spectrometer (APXS). These samples supplement the heterogeneous rocks of our earlier emulation work. The results confirm that PIXE provides high-accuracy concentrations for major and minor elements in homogeneous samples, and the results agree well with those from mono-minerals in the original APXS calibration. A second X-ray detector was added to the system to extend the emulation to the X-ray fluorescence branch of the APXS. The GRMs analyzed using this detector have relatively high concentrations of the trace elements copper, zinc, rubidium, strontium or zirconium. Our PIXE concentrations were compared to values provided by both the GRM suppliers and an independent corporation. Agreement was good in most cases, with individual deviations attributed mainly to inaccuracies in these reference concentrations.