Comparative study of X-ray fluorescence signal collection by collimators of two types

The response signal collection functions in a confocal setup of the X-ray fluorescence (XRF) tomography have been modeled for a polycapillary collimator and a multichannel collimator fabricated by means of microelectronic technology (MT). The dimensions of the effective collection region for the two types of collimators are compared. For the MT-fabricated device, a fraction of X-ray photons transmitted due to the total external reflection from channel walls has been evaluated. It is shown that, for a proper choice of parameters, the contribution of these photons to the collection function is negligibly small.