Experiments with Supersonic Beams as a Source of Cold Atoms

it does not need to be seeded into another carrier gas; a pure neon beam is used. To
reduce the initial velocity, the nozzle is cooled to 77 K. A 50 psi backing pressure is
used in these experiments.
4.4.2 18 Stage Coil Design
As noted above, to significantly slow a beam of metastable neon from ≈ 500m/s
fields of several Tesla per coil are desired. To produce these fields, a pulsed electro-
magnetic coil is constructed which is modeled on the coil that drives the plunger
in the Even-Lavie nozzle. The coil consists of 30 windings (6 layers of 5 turns) of
.5 mm diameter Kapton insulated copper magnet wire. The wire is wound around a
hollow Vespel cylinder with 50 μm wall thickness and 3 mm outer diameter. The coil
is located between two Permendur discs (Permendur 49, ASTM-A-801 Type 1, from
Carpenter Technology), one 3 mm thick, and the other 2.5mmthick, both10mmin
diameter, and is surrounded by a 3 mm thick soft magnetic steel shell. Permendur is
a high magnetic saturation material with a saturation value of 2.3 T, which confines
the field lines and increases the peak field inside the coil. The reason that one disc is
made thinner than the other is that the bottom of the soft steel shell is .5mm thick,
and so there is 3mm of magnetic steel on each side of the coil. Additionally, a Kapton
disc is inserted in between the coil and each Permendur disc, which helps to protect
the insulation of the wire. The entire coil is held together using Epo-Tek H77 epoxy,
which is a UHV compatible thermally conductive epoxy. A CAD image of the coil is
shown in figure 4.9.
The peak current in the coil is measured to be 400 A. Because the coil is
surrounded by non-linear ferromagnetic materials, the field profile of the coil is very
difficult to calculate analytically. As such, the field is instead calculated numerically
using finite element analysis using the program COMSOL Multiphysics. This allows
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