Experiments with Supersonic Beams as a Source of Cold Atoms

Figure 5.8: Photograph of the trapping coils wound around the chamber. The coils
are held in place with epoxy, and wrapped with an epoxied nylon cloth. Delrin clamps
on either side of the trap hold the coils in position.
5.2.2.2 Trapping Coil Geometry and Fields
Each trapping coil consists of 48 turns (8 layers of 6 turns) of Kapton insulated
copper tubing. Each coil is 1.57cm long and has a bore of 1.05cm. The outer diameter
of each trapping coil is 4.44cm. The wires have a 2.4mm outer diameter and an inner
diameter of 1.2 mm. Using hollow wires allows the coils to be cooled by running
distilled water through the core of the wires themselves. The water flow rate through
the coils is 5 ml/s. This amount of cooling allows the coils to be run with 200 A of
steady state current. Each coil has a measured resistance of 0.028 mΩ, meaning that
the water cooling is capable of removing a little more than 1100 W. Given that this
much power can be removed from each coil, at a repetition rate of 0.5Hz(given by
the coilgun coils) the trap coils can be operated at their full current of 450 A for up
to 300 ms without over-heating.
The coils are wound around in place around the trapping chamber, since the
bore of the coil is too small for them to slide over the flanges of the chamber. They
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