Développement de détecteurs de neutrons ultra-froids et d'un système d'analyse de polarisation pour la mesure du moment électrique dipolaire du neutron

Abstract : This thesis was performed in the context of a project aiming to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute. Two aspects have been studied: The detection and the polarization analysis of ulracold neutrons. Three types of detectors have been tested at the Institut Laue-Langevin (ILL): The Cascade-U (GEM technology), the 3He gas detector and 6Li-doped glass scintillators (GS family). Their detection efficiency and their background sensitivity have been measured. The GS10 scintillator is competitive with the 3He gas detector under the conditions realized with the EDM spectrometer. A GS3/GS20 scintillator stack has enabled to improve the neutron/gamma discrimination. It has been found 20% less efficient than the 3He gas detector under the EDM spectrometer. The Cascade-U detector has been observed to be 20% less efficient than a 500 microns thick GS10 glass as confirmed by simulations. A new system for simultaneous spin analysis is presented. It consists of two independent detection systems (arms) which are each made of an adiabatic spin flipper, a spin analyzer, and a detector. The arms detect opposite spin components, allowing the simultaneous counting of both neutron spin orientations. A prototype mounted in horizontal configuration has been tested at ILL. The analyzing power of both arms has been measured to be 80%. The transmission of the system without spin analyzers has been found to be 50%.
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G. Rogel. Développement de détecteurs de neutrons ultra-froids et d'un système d'analyse de polarisation pour la mesure du moment électrique dipolaire du neutron. Physique Nucléaire Théorique [nucl-th]. Université de Caen, 2009. Français. ⟨tel-00434416⟩

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