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|Type:||Artigo de periódico|
|Title:||A thermal neutron interferometer of the Fabry-Perot type|
|Abstract:||A new thermal neutron Fabry-Perot interferometer (FPI) similar to that proposed for hard X-rays by the same authors is proposed. Both devices consist of two thin parallel crystals separated by a nondiffracting gap. Bragg angles in both cases are very close to pi/2. While for X-rays the thickness of the plates is of the order of a few mu m, for neutrons it is one to two orders of magnitude larger. Then, the actual construction of the new interferometer should not impose the difficulties found for X-rays. The transmission profile shows the usual FPI transmission resonances. By changing the thickness of the mirrors and the dimensions of the gap, the energy width of these resonances can be controlled from being rather broad, of the order of the Darwin width, Delta E/E approximate to 10(-6), to the extremely narrow theoretical limit of Delta E/E approximate to 10(-9). The values may be changed within these Limits, either by the choice of the crystal or of the reflection involved and by changing the dimensions of the gap and plate thicknesses. The examples calculated here concentrate on silicon crystal slabs which are cheap and relatively easy to cut down to the required thickness. While the numerical results given are valid only for this material, the analysis made points out to various features of more general validity. In order to design an experiment the diffraction profiles are studied a) for constant plate thickness and varying gap and b) for constant gap and varying plate thickness. The results are presented in the text. It is shown that within limits, the effect of roughness of the crystal surfaces does not significantly alter the interferometer performance.|
|Editor:||Akademie Verlag Gmbh|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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