Design and simulation of a source of cold cadmium for atom interferometry

Abstract

We present a novel optimised design for a source of cold atomic cadmium, compatible with
continuous operation and potentially quantum degenerate gas production. The design is based on
spatially segmenting the first and second-stages of cooling with the the strong dipole-allowed 1S0-1P1
transition at 229 nm and the 326 nm 1S0-3P1 intercombination transition, respectively. Cooling at
229 nm operates on an effusive atomic beam and takes the form of a compact Zeeman slower (∼5 cm)
and two-dimensional magneto-optical trap (MOT), both based on permanent magnets. This design
allows for reduced interaction time with the photoionising 229 nm photons and produces a slow
beam of atoms that can be directly loaded into a three-dimensional MOT using the intercombination
transition. The efficiency of the above process is estimated across a broad range of experimentally
feasible parameters via use of a Monte Carlo simulation, with loading rates up to 108 atoms/s into
the 326 nm MOT possible with the oven at only 100 ◦C. The prospects for further cooling in a faroff-
resonance optical-dipole trap and atomic launching in a moving optical lattice are also analysed,
especially with reference to the deployment in a proposed dual-species cadmium-strontium atom
interferometer.

High flux strontium atom source

“…Instead, we used the picture from panel (b), from which we subtracted the signal from the trapped atoms, to isolate the 2 M MOT fluorescence in panel (a). We could thus estimate that the ZS enhances the 2D MOT by a factor of 14.2( 16) in the symmetric configuration, 21.3 (26) in the asymmetric one, and 35.4(28) in the two cooling beam frequency configuration, as reported in table 1. The best enhancement factor we measured is at least a factor 3 better than that reported for similar compact Sr [15,17] and Na [14] sources.…”

“…The atomic source design, which combines high flux, compactness, and low consumption, could be adapted straightforwardly to other atomic species where a ZS is required, and with a J = 0 ground state, such as Ca [25], Cd [26], and Yb [27,28]. For atoms with J̸ =0 ground states like Li, Na, Rb, addressing atomic losses due to optical pumping into non-decelerated magnetic sub-levels remains a challenge, especially near zero magnetic field and, for the two frequency components ZS, where the magnetic field gradient changes sign.…”