In the analysis of the original paint fragment, if the elements Cl,
Ti and Zn were in the confocal volume at the same time, the XRF of
both Ti and Zn could excite the XRF of Cl; moreover, the XRF of Zn
could excite the XRF of Ti. When the repaired paint fragment was
analyzed, if the elements Cu, Fe and Zn were in the confocal
volume at the same time, the XRF of both Cu and Zn could excite
the XRF of Fe. Such enhancement effects can be estimated and
modified by the method developed by Sokaras and Karydas
(2009), which is based on an ab initio mathematical formulation,
or the method developed by Czyzycki et al.(2011), which uses a
Monte Carlo simulation code. Furthermore, a novel confocal MXRF
spectrometer based on polycapillary X-ray optics might be integrated with a portable X-ray tube operating at low power. Such an
MXRF spectrometer could be used to nondestructively analyze the
multiple layers of paints on vehicles in situ.