Design of a millimetre-scale magnetic surface trap for cold atoms

We study a novel millimetre-scale magnetic trap for ultracold atoms, in which the current carrying conductors can be situated outside the vacuum region, a few mm away from the atoms. This design generates a magnetic field gradient in excess of 1000 G cm−1 at a distance of 2 mm from the conductors. We perform electromagnetic and thermo-mechanical characterization using finite element methods. The predicted behaviour has been verified by electrical and thermal measurements on a prototype, but has not been implemented on an apparatus with cold atoms. Operating this trap at the highest gradient allows rapid evaporative cooling comparable to that achieved by atom chips.