P 20 ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012)
SIMULATIONS OF X-RAY TRANSMISSION IN POLYCAPILLARIES FOR SYNCHROTRON RADIATION APPLICATIONS
P. Jagodzi´nski1∗, M. Pajek2, D. Bana´s2, A. Kubala-Kuku´s2, J. Szlachetko2,3, J.-Cl. Dousse4, J. Hoszowska4, Y. Kayser4, and S. Nowak4
1Department of Physics, Kielce University of Technology, Tysi¸aclecia PP 7, 25–314 Kielce, Poland
2Institute of Physics, Jan Kochanowski University, ´Swi¸etokrzyska 15, 25–406 Kielce, Poland
3Swiss Light Source, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
4Department of Physics, University of Fribourg, Chemin du Mus´ee 3, CH–1700 Fribourg, Switzerland Keywords: Monte-Carlo simulations, ray-tracing, X-ray polycapillary optics, external total reflection,
synchrotron radiation
∗e-mail : jagodzin@tu.kielce.pl
Polycapillary optics is a widely used technology for forming and guiding X-ray beams. In recent years the development of the polycapillary optics has become an active direction for X-ray research due to its wide potential applications in many fields, such as X-ray diffraction and fluorescence tech- niques and X-ray focusing optics for synchrotron ra- diation. The polycapillary consists of thousands of hexagonal glass tubes curved and arranged in the space. The incident X-rays can be transmitted in polycapillary by multiple total reflections on the in- ternal surface of the tubes occurring at glancing an- gle smaller than the critical angle of total external reflection [1].
The main parameters describing the polycapil- lary properties are the transmission efficiency, the divergence of outgoing photon beam, the focal dis- tance and spot size. The polycapillaries can be used for focusing a parallel beam, e.g. a synchrotron ra- diation beam, and for forming a parallel beam of photons emitted from a localized (e.g. point-like) X-ray source. Generally, the properties of the X- rays beam transmitted through a polycapillary de- pend on the source size and the energy of the X-rays as well as a shape of the polycapillary, length, fo- cal distance and the sizes of its entrance and exit openings (Fig. 1). The other factors affecting the transmission process include the capillary material quality and surface roughness.
The influence of the above mentioned factors on the polycapillary properties were studied in the present work by using the Monte-Carlo simulation technique. The aim of this research was to develop the software to predict and visualize the process of propagation of X-rays through a polycapillary op- tical system. The present calculations can predict a distribution of X-rays transmitted by a polycap- illary at arbitrary position behind its exit plane.
In the Monte-Carlo calculations different proper- ties of a transmitted photon beam were discussed in details. Consequently, the transmission efficiency, photon beam divergence, sizes of focal distance and spot were calculated for various X-ray energies in the range 1 – 10 keV. Generally, the Monte-Carlo simulations predict reasonable well the main char-
acteristics of the polycapillary and the parameters of the outgoing photon beam.
Performed calculations were compared with ex- perimental results concerning the application of polycapillary X-ray optics for focusing of syn- chrotron radiation and excited in the sample X- ray fluorescence. In particular, simulations of the properties of a polycapillary based flat-crystal X-ray wavelength dispersive spectrometer (WDS) [2] in- stalled at the ESRF ID21 X-ray Micro-spectroscopy Beamline and, in second case, a polycapillary used for focusing of the synchrotron radiation beam for grazing emission X-ray fluorescence (GEXRF) experiments [3] at ID21 beamline using a high- resolution von Hamos spectrometer [4] will be de- scribed in details. Finally, the results obtained us- ing discussed polycapillary X-ray optics will be pre- sented.
Figure 1 : Input parameters for polycapillary simula- tions.
References
[1] R. Klockenk¨amper, Total-Reflection X-ray Fluores- cence Analysis (Wiley Interscience, John Wiley &
Sons, USA, 1997).
[2] J. Szlachetko et al., “Wavelength-dispersive spec- trometer for X-ray micro-fluorescence analysis at the X-ray Microscopy beamline ID21 (ESRF),” J. Syn- chrotron Rad. 17 (2010) 400 – 408.
[3] Y. Kayser et al., “Depth profiling of low energy P, In and Sb implants using synchrotron radiation based high-resolution micro-GEXRF,” EGAS 2011 conf.
[4] J. Hoszowska et al., “High Resolution von Hamos Crystal X-ray Spectrometer,” Nucl. Instrum. Meth- ods Phys. Res. A 376 (1996) 129 – 138.
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