18 research outputs found
A Storage Ring for Neutral Atoms
We have demonstrated a storage ring for ultra-cold neutral atoms. Atoms with
mean velocities of 1 m/s corresponding to kinetic energies of ~100 neV are
confined to a 2 cm diameter ring by magnetic forces produced by two
current-carrying wires. Up to 10^6 atoms are loaded at a time in the ring, and
7 revolutions are clearly observed. Additionally, we have demonstrated multiple
loading of the ring and deterministic manipulation of the longitudinal velocity
distribution of the atoms using applied laser pulses. Applications of this ring
include large area atom interferometers and cw monochromatic atomic beam
generation.Comment: 4 pages, 5 figure
Superfluid toroidal currents in atomic condensates
The dynamics of toroidal condensates in the presence of condensate flow and
dipole perturbation have been investigated. The Bogoliubov spectrum of
condensate is calculated for an oblate torus using a discrete-variable
representation and a spectral method to high accuracy. The transition from
spheroidal to toroidal geometry of the trap displaces the energy levels into
narrow bands. The lowest-order acoustic modes are quantized with the dispersion
relation with . A condensate
with toroidal current splits the co-rotating and
counter-rotating pair by the amount: . Radial dipole excitations are the lowest energy dissipation modes.
For highly occupied condensates the nonlinearity creates an asymmetric mix of
dipole circulation and nonlinear shifts in the spectrum of excitations so that
the center of mass circulates around the axis of symmetry of the trap. We
outline an experimental method to study these excitations.Comment: 8 pages, 8 figure
Ground state and elementary excitations of single and binary Bose-Einstein condensates of trapped dipolar gases
We analyze the ground-state properties and the excitation spectrum of
Bose-Einstein condensates of trapped dipolar particles. First, we consider the
case of a single-component polarized dipolar gas. For this case we discuss the
influence of the trapping geometry on the stability of the condensate as well
as the effects of the dipole-dipole interaction on the excitation spectrum. We
discuss also the ground state and excitations of a gas composed of two
antiparallel dipolar components.Comment: 12 pages, 9 eps figures, final versio
Motional resonances in a molecular synchrotron
Contains fulltext :
99141.pdf (publisher's version ) (Open Access
Trapping neutral molecules in a traveling potential well
A series of pulsed electric fields can be arranged such that it creates a traveling potential well in which neutral dipolar molecules can be confined. This provides a method to transport, to decelerate, and to cool a sample of neutral molecules while maintaining the initial phase-space density. This method is described using the concept of phase stability. The oscillating motion of molecules in the traveling potential well, reaching a minimum velocity spread corresponding to a translational temperature of 4 mK, is experimentally observed
Tactile device based on opto-mechanical actuation of liquid crystal elastomers
Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. Thus, actuation can be produced on demand, forcing these phase changes. Here, we present a refreshable tactile device based on the opto-mechanical properties of liquid crystalline elastomers (LCE) with the capability to represent Braille characters and simplified graphical information. The actuators designed are based on the use of the stress gradient generated in the elastomer under illumination to exert a force on movable components. Additionally, hardware implementation and a communication software interface were developed to provide end users with a complete solution. Displacements of 0.8 mm with measured forces of up to 40 mN were reached without material degradation, proving not only the viability of the device but also the potential applications of this type of actuator.Scopu
Nematic opto-mechanical actuators for the fabrication of refreshable tactile systems
Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. We present a refreshable tactile system based on the opto-mechanical properties of liquid-crystalline elastomers (LCE) composites, with the capability to represent Braille characters and graphic information. The actuators designed are based on the stress gradient generated in the elastomer under illumination to exert a force on movable components. Hardware implementation and communication software interface were developed too to provide end users with a complete solution. First tests prove not only the viability of the device, but also the potential applications of this type of actuators.Scopu