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Méthodes de variation de contraste par polarisation nucléaire en diffusion de neutrons aux petits angles. Observation de domaines de nucléaire par diffusion de neutronspolarisation

Abstract : In this thesis we study the theoretical and experimental aspects of Contrast Variation by Nuclear Polarisation (CVNP) applied to small-angle neutron scattering. The basics of neutron scattering theory is developed by highlighting the origin of the CVNP method : the strong spin dependence of thermal neutron scattering, especially on protons. We also present the principles of NMR with a special attention on the method of dynamic nuclear polarisation by the solid effect which makes it possible to control the proton polarisation and therefore the contrast for neutron scattering. We present a theoretical study of the CVNP method called static which supposes that the nuclear polarisation is homogeneous in the sample and constant during the experiment. We show that it allows one to obtain partial structure functions of systems with multiple components, by carrying out several acquisitions with different polarisations on a single sample. For this purpose, we tested a simple device to stabilize the nuclear polarisation. We describe finally a new application of the CVNP method called dynamic. In a solution of deuterated glycerol-water containing a small concentration of paramagnetic centres, we showed the existence of domains of polarised protons at the onset of dynamic polarisation. This reinforces considerably the coherent scattering of paramagnetic centres. We describe the theoretical reasons explaining the appearance of these domains of polarisation, as well as the various techniques used to observe them by neutron scattering.
Keywords : SPEC-S02/087
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Theses
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https://tel.archives-ouvertes.fr/tel-00002103
Contributor : Marc Gingold <>
Submitted on : Tuesday, April 15, 2003 - 2:40:23 PM
Last modification on : Friday, October 23, 2020 - 4:37:11 PM
Long-term archiving on: : Monday, September 20, 2010 - 11:31:17 AM

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  • HAL Id : tel-00002103, version 2

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Edouard Leymarie. Méthodes de variation de contraste par polarisation nucléaire en diffusion de neutrons aux petits angles. Observation de domaines de nucléaire par diffusion de neutronspolarisation. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00002103v2⟩

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