Calculation of the transfer efficiency between dual magneto-optical traps and simulation of a Ioffe trap for Bose–Einstein condensation

Abstract

We consider the problem of transferring a cold atomic cloud from a low-vacuum chamber to an ultra-high-vacuum (UHV) chamber, where it can be recaptured and cooled to the transition temperature for Bose–Einstein condensation (BEC). Our calculation assumes an initial Maxwell–Boltzmann velocity distribution for the thermal cloud and a Gaussian spatial density distribution that is characteristic of magneto-optical traps (MOTs). Using a coordinate transformation we find the density of the recaptured atomic cloud as a function of time. This allows us to investigate the effect of experimental parameters on the transfer efficiency. These parameters include the distance of separation between the two chambers, the duration of the initial on-resonant laser used to push the thermal cloud, and the initial cloud temperature. We also present numerical simulations of the magnetic field due to a simplified Ioffe–Pritchard (IP) trap that has recently been used to obtain BEC using laser-cooling techniques. This trap converts a quadrupole magnetic field into an IP configuration using the magnetic field of a conical solenoid placed orthogonally to the axis of symmetry of a pair of quadrupole coils. Our results are suitable for small experimental groups interested in achieving BEC. PACS No.: 03.75