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Collisions in a cloud of metastable helium near quantum degeneracy

Signe Seidelin 1 
1 laboratoire Charles Fabry de l'Institut d'Optique / Optique atomique
LCFIO - Laboratoire Charles Fabry de l'Institut d'Optique
Abstract : This thesis presents an experimental study of an atomic cloud in the vicinity of Bose-Einstein condensation. The atoms used in our experiment are special in the sense that they are metastable -- we use metastable helium. The metastability opens the door for using new and original detection methods. Due to their internal energy, the atoms can be detected electronically by means of a micro-channel plate. The use of metastable helium is also interesting due of the presence of ionizing collisions in the sample. The He+ ions produced in collisions between the metastable atoms can be detected in real-time, and the ion signal constitutes an alternative and useful diagnostic. In particular, this signal allows one to identify very precisely the Bose-Einstein condensation threshold. One of the advantages of using this signal to probe the cloud, is its ''non-invasive" nature: observing the ions does not at all alter the natural evolution of the cloud, in contrast to the ordinary detection technique which consists of releasing the atoms from the trap and then imaging the cloud. In this thesis, by using the new diagnostics based on the ion signal, we have measured some important parameters governing the collisions, and thereby the behavior of the cloud: the ionizing rate constants and the scattering length.
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Submitted on : Thursday, December 2, 2004 - 8:54:44 PM
Last modification on : Saturday, June 25, 2022 - 11:12:41 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:39:32 PM


  • HAL Id : tel-00007611, version 1


Signe Seidelin. Collisions in a cloud of metastable helium near quantum degeneracy. Atomic Physics [physics.atom-ph]. Université Paris Sud - Paris XI, 2004. English. ⟨tel-00007611⟩



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