Odile Robach, Jean-Sébastien Micha, Olivier Ulrich, Olivier Geaymond, Olivier Sicardy, Jürgend Härtwig, François Rieutord
White beam x-ray Laue microdiffraction allows fast mapping of crystal orientation and strain fields in polycrystals, with a submicron spatial resolution in two dimensions. In the well crystallized parts of the grains, the analysis of Laue spots positions provides the local deviatoric strain tensor. In the parts with larger micro-misorientations, the spots shape and the orientation gradients (spots displacements) provide the density of unpaired dislocations (Geometrically Necessary Dislocations (GND's)). The hydrostatic part of the strain tensor, and the total dislocation density, may also be obtained, but more slowly, by measuring the energy profiles of the Laue spots using a variable-energy monochromatic beam. A new method is presented for the measurement of energy profiles, which offers mostly the same performances as the monochromatic method, with two advantages : i) the simultaneous measurement of the energy profiles and the Laue pattern; ii) the access to the energy profiles of a large number of spots with a small angular range. The method uses a thin rotating single crystalline diamond plate - the multi-color filter, installed upstream of the microfocussing optics. This diamond simultaneously diffracts a large number of discrete energies (forming a comb), and causes their attenuation in the - initially white - incident beam. The filter rotation causes a shift of the comb and allows to successively attenuate the variious Laue spots of the sample. The position of the filtered-out energies at each rotation step is obtained from the diamond Laue pattern, measured with a second 2D detector. This article demonstrates the feasibility of the multi-color filter - "Rainbow" - method, and shows a first test of measurement of a known lattice parameter.
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http://arxiv.org/abs/1207.2868
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