Determination of X-ray compression efficiency of a thin film X-ray waveguide structure using marker layer fluorescence M.K. Tiwari ⁎ , M. Nayak, G.S. Lodha, R.V. Nandedkar Synchrotron Utilisation and Materials Research Division, Raja Ramanna Centre For Advanced Technology, Indore-452013, India Received 7 August 2006; accepted 12 February 2007 Available online 24 February 2007 Abstract We demonstrate that a thin marker layer, sandwiched in the guiding medium of a thin film planner X-ray waveguide structure, can be used to determine X-ray compression efficiency for a particular excitation mode. It can also be used in evaluating the transmission efficiency of waveguide structure and for the determination of X-ray intensities reaching the waveguide exit. This approach has been applied for determining X- ray compression and transmission efficiency of a Mo/B 4 C/Mo based X-ray waveguide structure, by inserting a thin Fe marker layer. © 2007 Elsevier B.V. All rights reserved. PACS: 41.50.+h; 68.49.Uv; 68.65.Ac; 78.70.En Keywords: X-ray waveguide; X-ray standing wave; Multilayer; X-ray fluorescence 1. Introduction Spiller and Segmüller [1] for the first time demonstrated using laboratory X-ray source that waveguide structures can be fabricated for hard X-rays and they can be used as efficiently as optical waveguide. Later on, some other groups fabricated and tested such structures on synchrotron source [2–4]. Recently, X- ray waveguide structures have attracted considerable interest due to their potential application in the field of micro beam X- ray fluorescence, X-ray imaging and scattering [5–10], as they can provide highly coherent and intense beams confined in one or two dimensions. In conventional focusing devices (e.g. Kirkpatrick–Baez optics, capillary optics, Fresnel zone plate) focal spot demagnification depends on the source size. X-ray waveguide provides beam dimensions independent of source size. This unique property of X-ray waveguide structure allows the realization of a few nm size beams in the hard X-ray region [11]. A planner thin film X-ray waveguide structure simply consists of three layers of the two different materials deposited alternately on a flat surface. Different electromagnetic modes can be excited in the guiding layer according to condition; 2d sin θ = nλ, where λ is wavelength of incident radiation, θ is grazing incidence angle formed at the guiding layer surface, d is the thickness of guiding medium and the order number n describes the number of guided modes. These guided modes travel along the waveguide length. Usually, X-ray compression gain and transmission efficiency of a thin film X-ray waveguide structure is realized by measuring ratio of total intensity reaching at the waveguide exit to that of incident primary intensity [12–16]. During recent years, several material combinations have been appraised with the aim to increase the X-ray compression gain as well as transmission efficiency of thin film X-ray waveguide structure. Feng et al. [4] reported photon flux enhancement ∼ 20 times for 11.83 keV X-ray energy using SiO 2 /Ployimide/Si structure. Even, structures comprising of less absorbing materials like C/ C/C and C/Be/C have been examined [17]. X-ray compression in Ni/diamond-like Carbon/Ni structure has been determined by Pelliccia et al. [18] using laboratory X-ray sources. Jark and Di Fonzo [19] recently, performed a detailed study to determine the transmission of guided intensity achieved in the waveguide medium. They reported ∼ 50% transmission for Mo/Be/Mo waveguide structures for the photon energy 13–20 keV. It is not feasible to measure directly the electromagnetic field intensity distribution inside a waveguide structure. However, by Spectrochimica Acta Part B 62 (2007) 137 – 144 www.elsevier.com/locate/sab ⁎ Corresponding author. Tel.: +91 731 2442124; fax: +91 731 2442100. E-mail address: mktiwari@cat.ernet.in (M.K. Tiwari). 0584-8547/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2007.02.009