Atom chips are devices used to magnetically trap and manipulate ultracold atoms
and Bose-Einstein condensates near a surface. In particular, permanent magnetic film
atom chips can allow very tight confinement and intricate magnetic field designs while
circumventing technical current noise. Research described in this thesis is focused
on the development of a magnetic film atom chip, the production of Bose-Einstein
condensates near the film surface, the characterisation of the associated magnetic
potentials using rf spectroscopy of ultracold atoms and the realisation of a precision
sensor based on splitting Bose-Einstein condensates in a double-well potential.
The atom chip itself combines the edge of a perpendicularly magnetised GdTbFeCo
film with a machined silver wire structure. A mirror magneto-optical trap collects
up to 5 x 108 87Rb atoms beneath the chip surface. The current-carrying wires
are then used to transfer the cloud of atoms to the magnetic film microtrap and
radio frequency evaporative cooling is applied to produce Bose-Einstein condensates
consisting of 1 x 105 atoms.
We have identified small spatial magnetic field variations near the film surface that
fragment the ultracold atom cloud. These variations originate from inhomogeneity in
the film magnetisation and are characterised using a novel technique based on spatially
resolved radio frequency spectroscopy of the atoms to map the magnetic field landscape
over a large area. The observations agree with an analytic model for the spatial decay
of random magnetic fields from the film surface.
Bose-Einstein condensates in our unique potential landscape have been used as a
precision sensor for potential gradients. We transfer the atoms to the central region
of the chip which produces a double-well potential. A single BEC is formed far from
the surface and is then dynamically split in two by moving the trap closer to the
surface. After splitting, the population of atoms in each well is extremely sensitive to
the asymmetry of the potential and can be used to sense tiny magnetic field gradients
or changes in gravity on a small spatial scale.
| Identifer | oai:union.ndltd.org:ADTP/216640 |
| Date | January 2007 |
| Creators | Whitlock, Shannon, n/a |
| Publisher | Swinburne University of Technology. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.swin.edu.au/), Copyright Shannon Whitlock |
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