Experiments to Control Atom Number and Phase-Space Density in ...

they have time to rethermalize to thermodynamic equilibrium. Thus T (z)
O
representation of the velocity distribution along the vertical dimension.
is a direct
Figure 5.7: Atom number (black squares) and vertical temperature (blue circles) of
atoms trapped in the optical trough as a function hp (height above the demon beam
above the trough).
The largest number of atoms can be transferred into the optical trap at a demon
beam position of hp = 100 µm, while the point corresponding to the highest phase-
space density is located at hp = 41 µm. To understand the temperature and transfer
efficiency curves, consider the atoms being transferred into the |F = 1,mF = 1〉 state.
After the atoms encounter the demon beam they regain kinetic energy by falling into
the bottom of the trough. For a demon beam height hp > 100 µm, this energy gain is
sufficient to overcome the optical potential created by the optical trough, resulting in
loss from the gravito-optical trap. One might therefore think that in order to minimize
this energy gain, the height of the demon beam hp should be as close to the trough
vertex as possible. However, as the demon beam gets closer to the trough vertex, the
potentials of the demon beam and the optical trough beams start to overlap. This means
that fewer atoms are reaching the demon beam, leading to a reduced transfer efficiency.
By reducing the height hp below zero, the atoms need to climb up the potential created
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