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Theses

3He in extreme conditions : from fundamental physics to applications
in astrophysics

Abstract : This work is composed of three different parts: in the first part, a long term project on a dark matter detector prototype based on superfluid 3He (ULTIMA) is continued, and several precious observations for the operation of a future large detector are presented. The importance of covering the bolometer cell surfaces with 4He, as solid layers of 3He drastically reduce the sensitivity, is demonstrated. The systematic measurement of the influence of the magnetic field on the energy calibration is presented. Most importantly, a difference of the pulse shape for different incident particles has been observed and studied. This possibly provides a powerful discrimination criterion for a future dark matter detector. In a second part, the existing setup is used to do measurements on fundamental 3He physics. Firstly, the heat capacity of adsorbed layers of 3He is measured at ultra low temperatures and in the presence of magnetic fields. Secondly, the fast transition from the normal to the superfluid phase after a local heating by a neutron capture reaction is studied. The results are interpreted in terms of the Kibble-Zurek vortex creation scenario. In the third part, the influence on the superfluid states of the confinement of 3He in anisotropic aerogel is studied. Using NMR techniques, predictions of the appearance of a new phase labeled polar phase are tested, and evidence for the observation of a new precessing mode is presented.
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https://tel.archives-ouvertes.fr/tel-00371099
Contributor : Johannes Elbs <>
Submitted on : Thursday, March 26, 2009 - 2:46:15 PM
Last modification on : Thursday, November 19, 2020 - 1:01:00 PM
Long-term archiving on: : Thursday, June 10, 2010 - 5:47:02 PM

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  • HAL Id : tel-00371099, version 1

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Johannes Elbs. 3He in extreme conditions : from fundamental physics to applications
in astrophysics. Condensed Matter [cond-mat]. Université Joseph-Fourier - Grenoble I, 2007. English. ⟨tel-00371099⟩

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