Applications of cold, magnetically-guided atomic beams

P. Cren, C.F. Roos, A. Aclan +2 more

Hiroki Hirano, Kazuki Horiguchi, Hi Tou +1 more

Georg A. Raithel

Anoush Aghajani-Talesh

This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 µK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

Anoush Aghajani-Talesh, Markus Falkenau, Axel Griesmaier +1 more

The capture of a moving atom by a non-dissipative trap, such as an optical dipole trap, requires the removal of the excessive kinetic energy of the atom. In this paper, we develop a mechanism to harvest ultra-cold atoms from a guided atom beam into an optical dipole trap by removing their directed kinetic energy. We propose a continuous loading scheme where this is accomplished via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. We theoretically investigate the application of this scheme to the transfer of ultra-cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap. We discuss the realization of a suitable magnetic field configuration. Based on numerical simulations of the loading process, we analyse the feasibility and efficiency of our loading scheme.

D. P. Rhodes, Gavin P. T. Lancaster, J. Livesey +3 more