Reaching for copper pigments speciation with High Resolution Energy Dispersive PIXE

The C²TN XMS-PIXE system based on a first generation X-ray Microcalorimeter Spectrometer (XMS) having 1.5% relative energy resolution at Si Kα 1.739 keV and 0.5% relative energy resolution at Fe Kα 6.403 keV, became operational in 2008, presaging various developments to emerge from its use and from connected or related but independent advancements by other laboratories. More than ten years having passed since the C²TN XMS-PIXE system first results, knowledge about XMSs use for PIXE has grown meaningfully and new applications are now envisaged and in progress. In the present work, results on the analysis of different copper compounds are presented, and used as an assessment of the capacity of High Resolution Energy Dispersive PIXE (HiRED-PIXE) to provide answers to the problem of copper pigments speciation in Cultural Heritage studies. Related issues of XMS spectra generation and calibration are discussed, as well as first generation systems limitations and its overcome by the use of second and third generation systems.