Abstract:
The cloud of cold atoms produced by a Magneto-Optical Trap is known to exhibit instabilities. We examine in this paper in which limits it could be possible to realize an experimental trap similar to the configurations studied theoretically, i.e. mainly traps where one direction is privileged. We study the static behavior of an anisotropic trap, where anisotropy results essentially from the use of two different laser frequencies for the arms of the trap. Such a trap has very surprising behaviors, in particular the cloud disappears for some laser frequencies, while it exists for smaller and larger frequencies. A model is build to explain these behaviors. We show in particular that, to reproduce the experimental observations, the model has to take into account the cross saturation effects. Moreover, the couplings between the different directions cannot be neglected.

Abstract:
We have observed self-sustained radial oscillations in a large magneto-optical trap (MOT), containing up to $10^{10}$ Rb$^{85}$ atoms. This instability is due to the competition between the confining force of the MOT and the repulsive interaction associated with multiple scattering of light inside the cold atomic cloud. A simple analytical model allows us to formulate a criterion for the instability threshold, in fair agreement with our observations. This criterion shows that large numbers of trapped atoms $N>10^9$ are required to observe this unstable behavior.

Abstract:
Magneto-impedance (MI) effects have been observed for amorphous Fe73.5Nb3Cu1Si13.5B9 ribbon which has been excited by an a.c. magnetic field parallel to the length of the ribbon. Maximum relative change in MI as large as -99% was observed which has never been reported before. The relative change in MI, when plotted against scaled field was found to be nearly frequency independent. A phenomenological formula for magneto-impedance, Z(H), in a ferromagnetic material, is proposed based on Pade approximant to describe the scaled behavior of MI.

Abstract:
Single caesium atoms in a large-magnetic-gradient vapour-cell magneto-optical trap have been identified. The trapping of individual atoms is marked by the steps in fluorescence signal corresponding to the capture or loss of single atoms. The typical magnetic gradient is about 29\,mT/cm, which evidently reduces the capture rate of magneto-optical trap.

Abstract:
The cloud of cold atoms obtained from a magneto-optical trap is known to exhibit two types of instabilities in the regime of high atomic densities: stochastic instabilities and deterministic instabilities. In the present paper, the experimentally observed deterministic dynamics is described extensively. Three different behaviors are distinguished. All are cyclic, but not necessarily periodic. Indeed, some instabilities exhibit a cyclic behavior with an erratic return time. A one-dimensional stochastic model taking into account the shadow effect is shown to be able to reproduce the experimental behavior, linking the instabilities to a several bifurcations. Erraticity of some of the regimes is shown to be induced by noise.

Abstract:
We propose and experimentally demonstrate a novel scheme to magneto-optically trap neutral atoms in a ring shaped trap that can be used to transfer atoms into a circular magnetic trap with high density. This inturn enables to evaporatively cool atoms and study the behaviour of ultra cold gases in a periodic 2-dimensional potential. The circular magneto-optical trap itself is also of interest to investigate the properties of magneto-optical trap of deformed shape, such as reduction of photon-reabsorption.

Abstract:
We present a novel technique for measuring the characteristics of a magneto-optical trap for cold atoms by monitoring the spontaneous emission from trapped atoms coupled into the guided mode of a tapered optical nanofiber. We show that the nanofiber is highly sensitive to very small numbers of atoms close to its surface. The size and shape of the MOT, determined by translating the cold atom cloud across the tapered fiber, is in excellent agreement with measurements obtained using the conventional method of fluorescence imaging using a CCD camera. The coupling of atomic fluorescence into the tapered fiber also allows us to monitor the loading and lifetime of the trap. The results are compared to those achieved by focusing the MOT fluorescence onto a photodiode and it was seen that the tapered fiber gives slightly longer loading and lifetime measurements due to the sensitivity of the fiber, even when very few atoms are present.

Abstract:
The cloud of cold atoms obtained from a magneto-optical trap is known to exhibit two types of instabilities in the regime of high atomic densities: stochastic instabilities and deterministic instabilities. In the present paper, the experimentally observed stochastic dynamics is described extensively. It is shown that it exists a variety of dynamical behaviors, which differ by the frequency components appearing in the dynamics. Indeed, some instabilities exhibit only low frequency components, while in other cases, a second time scale, corresponding to a higher frequency, appears in the motion of the center of mass of the cloud. A one-dimensional stochastic model taking into account the shadow effect is shown to be able to reproduce the experimental behavior, linking the existence of instabilities to folded stationary solutions where noise response is enhanced. The different types of regimes are explained by the existence of a relaxation frequency, which in some conditions is excited by noise.

Abstract:
In a recent paper, we have used the dark-spot Zeeman tuned slowing technique [Phys. Rev. A 62, 013404-1, (2000)] to measure the capture velocity as a function of laser intensity for a sodium magneto optical trap. Due to technical limitation we explored only the low light intensity regime, from 0 to 27 mW/cm^2. Now we complement that work measuring the capture velocity in a broader range of light intensities (from 0 to 400 mW/cm^2). New features, observed in this range, are important to understant the escape velocity behavior, which has been intensively used in the interpretation of cold collisions. In particular, we show in this brief report that the capture velocity has a maximum as function of the trap laser intensity, which would imply a minimum in the trap loss rates.

Abstract:
We present the design, implementation and characterization of a dual-species magneto-optical trap (MOT) for fermionic 6Li and 40K atoms with large atom numbers. The MOT simultaneously contains 5.2x10^9 6Li-atoms and 8.0x10^9 40K-atoms, which are continuously loaded by a Zeeman slower for 6Li and a 2D-MOT for 40K. The atom sources induce capture rates of 1.2x10^9 6Li-atoms/s and 1.4x10^9 40K-atoms/s. Trap losses due to light-induced interspecies collisions of ~65% were observed and could be minimized to ~10% by using low magnetic field gradients and low light powers in the repumping light of both atomic species. The described system represents the starting point for the production of a large-atom number quantum degenerate Fermi-Fermi mixture.