Experiments with Supersonic Beams as a Source of Cold Atoms

Figure 3.5: A CAD image of the detection chamber. The chamber is separated from
the rotor chamber by a 5 mm aperture. This provides differential pumping, keeping
the detection volume from experiencing too high a gas load from the direct beam.
The chamber is pumped by a 70 l/s turbo pump. Figure Courtesy Max Riedel.
is constructed from 1 inch thick stainless steel, and can be seen in figure 3.4. The
chamber disc is 112 cm in diameter and 12.7 cm high. Due to the large surface area
of the top and bottom of this disc, atmospheric pressure moves the top and bottom
of the chamber together by 4 mm when the chamber is under vacuum.
The final chamber section is the detection chamber, illustrated in figure 3.5.
The detection chamber is separated from the rotor chamber by a 5 mm aperture
constructed from a copper disc (used instead of an annular gasket where the rotor
chamber connects to the detection chamber). The detection chamber is pumped by
a 70 l/s Varian turbo pump, and houses the detector used to observe the beam when
it does not interact with the rotor. This detector is located 1.42 m from the nozzle.
The direct beam detector was originally directly connected to the rotor chamber, but
this negatively impacted detector performance, probably due to the significant gas
load entering the detection region without adequate pumping.
The entire apparatus is shown in figure 3.6. The support structures are made
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