Scanning-PIXE analysis of gold lace embroideries in a relic of St. Francis

In this work, we describe the compositional analysis performed by scanning-mode PIXE on the metal threads of a XIII century embroidery. The precious work analysed is the pillow-case used to cover the pillow, on which – according to tradition – St. Francis of Assisi was resting his head when he died. Measurements were performed in order to characterise the embroideries of the two sides and the passementerie in the lateral hems. Several areas, each of the order of two square millimetres, were scanned with a 3 MeV proton external beam of 20 μm size on target, using the external micro-beam facility of our laboratory, with list-mode acquisition. Analysis of elemental maps and spectra from selected homogeneous sub-areas allowed us to extract the quantitative composition of the gilded tape and estimates of its thickness.