Experiments with Supersonic Beams as a Source of Cold Atoms

500 l/s Turbo
Pump
Cold Cathode
Vacuum Gauge
Helium
Beam
Figure 3.4: A CAD image of the rotor chamber. The chamber is pumped by a 500 l/s
turbo pump (indicated). The chamber walls are 1 inch thick 304 stainless steel, and
the chamber disc is 112cm in diameter and 12.7cm high.
of 5 Hz (10 −8 torr when the nozzle is not operating). This is monitored by a cold
cathode vacuum gauge (not shown). The nozzle hangs from a pool type cryostat into
the center of the 6-way cross. The beam propagates 30cm to the 5cm skimmer, which
has a 5 mm aperture. From the skimmer, the beam passes into the rotor chamber,
which is connected to the nozzle chamber by a flexible bellows, allowing the helium
beam to be aligned to the rest of the experiment.
The rotor chamber has to accommodate the rotor, which is the key element
in the design of the chamber as a whole. As described in section 3.3.2, the rotor is
100.8 cm in diameter, and so the chamber needs to be large enough to allow it to spin
freely. In addition, the beam needs to enter the interaction region and be detected.
This led to a custom chamber design, as seen in figure 3.4. The chamber is pumped
by a 500 l/s Varian turbo pump that keeps the chamber at a pressure of 2 · 10 −8 torr
while the nozzle is firing (10 −9 torr when the nozzle is not operating). The chamber
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