%0 journal article
%@ 1094-4087
%A Chalupsky, J.,Krzywinski, J.,Juha, L.,Hajkova, V.,Cihelka, J.,Burian, T.,Vysín, L.,Gaudin, J.,Gleeson, A.,Jurek,  M.,Khorsand, A. R.,Klinger, D.,Wabnitz, H.,Sobierajski, R.,Stoermer, M.,Tiedtke, K.,Toleikis, S.

%D 2010
%J Optics express
%N 26
%P 27836-27845 
%R doi:10.1364/OE.18.027836
%T Spot size characterization of focused non-Gaussian X-ray laser beams
%U https://doi.org/10.1364/OE.18.027836
26 
%X We present a new technique for the characterization of non-Gaussian laser beams which cannot be described by an analytical formula. As a generalization of the beam spot area we apply and refine the definition of so called effective area (Aeff) [1] in order to avoid using the full-width at half maximum (FWHM) parameter which is inappropriate for non-Gaussian beams. Furthermore, we demonstrate a practical utilization of our technique for a femtosecond soft X-ray free-electron laser. The ablative imprints in poly(methyl methacrylate) - PMMA and amorphous carbon (a-C) are used to characterize the spatial beam profile and to determine the effective area. Two procedures of the effective area determination are presented in this work. An F-scan method, newly developed in this paper, appears to be a good candidate for the spatial beam diagnostics applicable to lasers of various kinds.