Laser cooling of a magnetically guided ultra cold atom beam

TL;DR

This paper demonstrates effective transverse laser cooling of a magnetically guided ultra cold chromium atom beam, significantly increasing phase space density and achieving temperatures below 65 microkelvin.

Contribution

It introduces a method combining magnetic guiding, tapering, and optical molasses to cool and compress an ultra cold atom beam while preventing atom losses.

Findings

Phase space density increased by over 30 times

Final temperatures below 65 microkelvin achieved

Cooling method preserves atom number and minimizes heating

Abstract

We report 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 microkelvin have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.