ISSN 1063-7850, Technical Physics Letters, 2012, Vol. 38, No. 5, pp. 452–455. © Pleiades Publishing, Ltd., 2012. Original Russian Text © Ya.L. Shabel’nikova, M.V. Chukalina, 2012, published in Pis’ma v Zhurnal Tekhnicheskoi Fiziki, 2012, Vol. 38, No. 10, pp. 6–13. 452 The method of X-ray fluorescence (XRF) tomog- raphy is applicable to investigations of a wide class of objects with any degree of structural ordering, which accounts for the increasing use of this analytical tool. The XRF tomography is capable of providing infor- mation on the distribution of chemical elements in an object with a high spatial resolution (on a micron level) and high sensitivity (on a ppm level) [1–3]. In a confocal setup of the XRF imaging, the object is probed with a focused X-ray beam. Under this excita- tion, atoms in the probed volume emit characteristic fluorescence photons. The intersection of the incident probing beam with the focal spot of a collimator (posi- tioned in front of the detector entrance window) determines a “focal volume” that is scanned over the object (Fig. 1a). The fluorescent response collected from this volume is measured by the detector. Then, processing of the XRF spectrum yields the concentra- tions of elements in the given volume of the sample. Polycapillary collimators have been used in experi- ments on confocal XRF imaging on synchrotrons (BESSY, DESY, ESRF) for about a decade (see, e.g. [1, 4]). This device represents an assembly of closely packed bent glass capillaries. At the front end of the collimator, all capillaries are directed toward a com- mon point—focus, while, at the rear end, the capillar- ies are parallel to each other. The operation of this col- limator is based upon the phenomenon of total exter- nal reflection (TER), whereby X-rays incident on the capillary walls at angles smaller than a certain critical Comparative Study of X-ray Fluorescence Signal Collection by Collimators of Two Types Ya. L. Shabel’nikova* and M. V. Chukalina Institute of Microelectronic Technology and Ultrahigh-Purity Materials, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: janeshabeln@yandex.ru Received January 10, 2012 Abstract—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. DOI: 10.1134/S1063785012050288 (a) (b) 1 2 y 0 –L 4 3 x S 1 2 y 4 3 x S Θ c Fig. 1. Schematic diagram illustrating calculations of the acceptance angle for (a) MT-fabricated and (b) polycapillary collimator: (1) X-ray beam, (2) fluorescence photons, (3) collimator, and (4) detector.