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Proceedings Paper

Global optimization and reflectivity data fitting for x-ray multilayer mirrors by means of genetic algorithms
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Paper Abstract

The x-ray reflectivity of a multilayer is a non-linear function of many parameters (materials, layer thicknesses, densities, roughness). Non-linear fitting of experimental data with simulations requires to use initial values sufficiently close to the optimum value. This is a difficult task when the space topology of the variables is highly structured, as in our case. The application of global optimization methods to fit multilayer reflectivity data is presented. Genetic algorithms are stochastic methods based on the model of natural evolution: the improvement of a population along successive generations. A complete set of initial parameters constitutes an individual. The population is a collection of individuals. Each generation is built from the parent generation by applying some operators (e.g. selection, crossover, mutation) on the members of the parent generation. The pressure of selection drives the population to include 'good' individuals. For large number of generations, the best individuals will approximate the optimum parameters. Some results on fitting experimental hard x-ray reflectivity data for Ni/C multilayers recorded at the ESRF BM5 are presented. This method could be also applied to the help in the design of multilayers optimized for a target application, like for an astronomical grazing-incidence hard X-ray telescopes.

Paper Details

Date Published: 5 January 2001
PDF: 9 pages
Proc. SPIE 4145, Advances in X-Ray Optics, (5 January 2001); doi: 10.1117/12.411624
Show Author Affiliations
Manuel Sanchez del Rio, European Synchrotron Radiation Facility (France)
Giovanni Pareschi, Osservatorio Astronomico di Brera (Italy)

Published in SPIE Proceedings Vol. 4145:
Advances in X-Ray Optics
Alan G. Michette; Andreas K. Freund; Tetsuya Ishikawa; Sebastian Oestreich; Derrick C. Mancini; Ali M. Khounsary; Derrick C. Mancini; Alan G. Michette; Sebastian Oestreich, Editor(s)

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