A GUPIX-based approach to interpreting the PIXE-plus-XRF spectra from the Mars Exploration rovers: II geochemical reference materials

Accurate Determination of Quantity of Material in Thin Films by Rutherford Backscattering Spectrometry

“…Spectrometers able to effectively quantify the energy spectra of scattered particles took a longer time to develop, but again the potential application to analytical chemistry was immediately recognised [21]. Xray fluorescence techniques are very well established today as routine analytical tools using both electron and X-ray excitation, but the equivalent technique using ion excitation is not so well developed despite many notable analytical successes: one example is the demonstration of the existence of hydrated minerals on Mars [22] using a detailed analysis of mixed XRF/α-PIXE data [23]; another is a forensic application of PIXE [24].…”

“Total IBA” – Where are we?

“…A portable XRF/PIXE has been reported [120], but in this work the XRF and PIXE data were handled separately. It is only quite recently that any sustained attempt has been made to integrate them [121] [122]. In this rather special case of the Mars Rovers, the data themselves are a mixture of XRF and PIXE because of the mixed radioactive source being used.…”

The instrumental blank of the Mars Science Laboratory alpha particle X-ray spectrometer

“…As an alternative approach, one can work with concentration offsets, which are the equivalent concentrations either deduced from the offset areas by the GUAPX spectrum processing software [4,5] or determined by other methods. Obviously, application of the closure rule is again necessary.…”

“…Obviously, application of the closure rule is again necessary. For a given sample, whether standard or unknown, the concentration of an element and its Xray peak area are related through so-called ''matrix terms'' [3][4][5] which describe the interactions of alpha particles and photons within that sample. We can define the ''sensitivity'' as the (sample-dependent) ratio of observed peak counting rate (cps) to concentration (wt.%).…”

“…On the assumption of a homogenous distribution of sample atoms on the micron scale of distance, a straightforward application of the X-ray yield equations from PIXE and XRF provides a complete elemental analysis of a geological sample. We have described in detail our transformation of the widely used GUPIX package [3] into a new code GUAPX [4,5] which fits the XRF + PIXE spectra from the APXS, accomplishes the appropriate matrix computations, and converts X-ray peak areas to element concentrations.…”