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Thomann, Pierre

Nom
Thomann, Pierre
Affiliation principale
Fonction
Professeur honoraire
Email
pierre.thomann@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/481

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  • Publication
    Accès libre
    First results with a cold cesium continuous fountain resonator
    (2001)
    Dudle, Gregor
    ;
    Joyet, Alain 
    ;
    Berthoud, Patrick
    ;
    Mileti, Gaetano 
    ;
    Thomann, Pierre 
    We report on the design, construction, and preliminary measurements on the resonator of a continuous Cs fountain frequency standard. The construction of the resonator is described, preliminary measurements of the available atomic flux, and of the beam temperature are presented, along with the first Ramsey fringes (width ≃1 Hz) obtained in this new type of fountain. We discuss theoretical aspects of the interrogation scheme with a special view on how aliasing or intermodulation effects are suppressed in a continuous fountain.
  • Publication
    Métadonnées seulement
    Bright, slow, and continuous beam of laser-cooled cesium atoms
    (1999)
    Berthoud, Patrick
    ;
    Fretel, Emmanuel
    ;
    Thomann, Pierre 
    By the moving molasses technique we have extracted laser-cooled cesium atoms in a continuous way directly from an optical molasses. The mean launching velocity is precisely tunable from 1 to 12 m/s. The atomic beam has a flux of 1.3 x 10(8) atom/s at 7 m/s and a longitudinal temperature of 70 mu K; which represents the highest flux and lowest velocity spread obtained so far in a continuous beam of cold atoms. These features makes it well suited for atomic fountains. The atomic flux can be slightly increased in a two-dimensional magneto-optical trap operation (+40%). A simple model accounts for the observed dependence of the flux with the magnetic-field gradient. [S1050-2947(99)51212-2].
  • Publication
    Métadonnées seulement
    An alternative cold cesium frequency standard: The continuous fountain
    (: Ieee-Inst Electrical Electronics Engineers Inc, 1999)
    Dudle, Gregor
    ;
    Mileti, Gaetano 
    ;
    Joyet, Alain 
    ;
    Fretel, Emmanuel
    ;
    Berthoud, Patrick
    ;
    Thomann, Pierre 
    We report on the primary frequency standard now under construction at the Observatoire de Neuchatel (ON). The design is based on a continuous fountain of laser-cooled cesium atoms, which combines two advantages: the negligible contribution of collisions to the inaccuracy and the absence of stability degradation caused by aliasing effects encountered in pulsed operation. The design is reviewed with special emphasis on the specific features of a continuous fountain, namely the source, the microwave cavity (TE021 mode), and the microwave modulation scheme, The possible sources of frequency biases and their expected contributions to the error budget are discussed. Based on present data, an accuracy in the low 10(-15) range and a short-term stability of 7 . 10(-14) are attainable simultaneously under the same operating conditions.
  • Publication
    Accès libre
    A continuous beam of slow, cold cesium atoms magnetically extracted from a 2D magneto-optical trap
    (1998)
    Berthoud, Patrick
    ;
    Joyet, Alain 
    ;
    Dudle, Gregor
    ;
    Sagna, N.
    ;
    Thomann, Pierre 
    Starting from a 2D magneto-optical trap where cesium atoms are permanently subjected to 3D sub-Doppler cooling and 2D magneto-optical trapping, we have produced a beam of cold atoms continuously extracted along the trap axis. The simplest extraction mechanism, presently used, is the drift velocity induced by a constant magnetic field. We have used this continuous beam of atoms to produce Ramsey fringes in a microwave cavity as a first demonstration of an atomic resonator operating continuously with laser cooled atoms. The shape of the resonance pattern allows an estimate of the axial temperature, typically 200 μK. The average velocity can be adjusted from 0.7 to 3 m/s; the trap-to-atomic-beam conversion efficiency is close to one.
  • Publication
    Accès libre
    Anisotropic magneto-optical trapping of atoms: capture efficiency and induced drift velocities
    (1996)
    Dudle, Gregor
    ;
    Sagna, N.
    ;
    Berthoud, Patrick
    ;
    Thomann, Pierre 
    An anisotropic magneto-optical trap is studied as the potential source of a continuous beam of laser-cooled atoms. Capture efficiency and cloud temperature are measured experimentally and found to be lower than in an isotropic situation with the same cooling parameters. Intensity imbalance and static magnetic field are investigated as possible extraction mechanisms. While only small drift velocities are induced by means of intensity imbalance, velocities of tens of cm s-1 are observed with a static magnetic field; the shape of the observed two-peaked velocity distributions is related to the average depth of local light-shift-induced potential wells.