Accumulation and thermalization of cold atoms in a finite-depth magnetic trap
We study the continuous accumulation of cold atoms from a magneto-optical trap (MOT) into a finite depth trap, consisting in a magnetic quadrupole trap dressed by a radiofrequency (RF) field.
arXiv:0612133 (2006) / Phys. Rev. A 76, 023406 (2007)
Chromium atoms (52Cr) in a MOT are continuously optically pumped by the MOT lasers to metastable dark states.
In the presence of a RF field, the temperature of the metastable atoms that remain magnetically trapped can be as low as 25μK, with a density of 1017atoms m−3, resulting in an increase of the phase-space density, still limited to 7.0×10−6 by inelastic collisions.
To investigate the thermalization issues in the truncated trap, we measure the free evaporation rate in the RF-truncated magnetic trap, and deduce the average elastic cross section for atoms in the 5𝐷4 metastable states, 𝜎𝑒𝑙=7.0×10−16 m2.
