4,316 research outputs found
Gimbal angle sensor
Detector flake located parallel to a slotted mask mechanical differentiator, senses the rotation of a gimballed reaction wheel mounting. As the gimbal moves light passes through the mask and strikes a section of the detector, the electrical output of which has been calibrated in terms of degrees of rotation
Supersonic flow with feeding of energy
The present work discusses the results of some experimental studies on the possibility of attenuating shock waves in a supersonic flow. The shock waves were formed by an external source of electrical energy. An electromechanical method is described that permits partial recovery of the expended energy
Accidental suppression of Landau damping of the transverse breathing mode in elongated Bose-Einstein condensates
We study transverse radial oscillations of an elongated Bose-Einstein
condensate using finite temperature simulations, in the context of a recent
experiment at ENS. We demonstrate the existence of a mode corresponding to an
in-phase collective oscillation of both the condensate and thermal cloud.
Excitation of this mode accounts for the very small damping rate observed
experimentally, and we find excellent quantitative agreement between experiment
and theory. In contrast to other condensate modes, interatomic collisions are
found to be the dominant damping mechanism in this case.Comment: 4 pages, 3 figure
Transition to the Giant Vortex State in an Harmonic Plus Quartic Trap
We consider a rapidly rotating Bose-condensed gas in an harmonic plus quartic
trap. At sufficiently high rotation rates the condensate acquires an annular
geometry with the superposition of a vortex lattice. With increasing rotation
rate the lattice evolves into a single ring of vortices. Of interest is the
transition from this state to the giant vortex state in which the circulation
is carried by only a central vortex. By analyzing the Gross-Pitaevskii energy
functional variationally, we have been able to map out the phase boundary
between these two states as a function of the rotation rate and the various
trapped gas parameters. The variational results are in good qualitative
agreement with those obtained by means of a direct numerical solution of the
Gross-Pitaevskii equation.Comment: 19 pages, 10 figure
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