Experiments with Supersonic Beams as a Source of Cold Atoms

(a) (b) (c)
Time
10 mm
Figure 5.7: This figure shows numerically calculated magnetic field profiles at different
points in the trapping sequence. In (a), the slowed bunch is approaching the trap
from the coilgun and both coils are turned on with the same polarity. The front
trapping coil is used as the final slowing coil. Once it is turned off, the atoms are
brought to rest at the center of the trapping volume by the rear trapping coil, as
illustrated in (b). At this point the front trapping coil is quickly switched back on
with the opposite polarity, creating a 100 mK deep trap quadrupole trap for the cold
atoms, which is shown in (c).
slowed packet has the proper velocity for it to come to rest in the center of the
trapping volume. At this point in the trapping sequence, the front trapping coil
will be quickly switched back on, but with the opposite polarity. This forms an
anti-Helmholtz quadrupole trap. The entire trapping sequence is shown in figure 5.7.
It may also be necessary to remove the trapped atoms from the trap in order
to detect them. To do this, the rear trapping coil can be turned off, leaving the front
trapping coil on. The field from the front trapping coil will repel the low-field-seeking
atoms out of the trap through the bore of the rear trapping coil. The rear trapping
coil can be switched back on with the opposite polarity once the atoms have passed
through the bore, which will continue accelerating the atoms into a detection surface
or volume.
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1.15 T
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