Experiments with Supersonic Beams as a Source of Cold Atoms

Figure 3.11: This plot shows the amplitude of the rotor vibration at several rotational
speeds. The vibrational amplitude measured by the laser is shown in red, while the
amplitude measured by the accelerometer outside the chamber is shown in black.
The dashed lines indicate observed resonances as observed by either the laser or the
accelerometer. The solid line is a Lorentzian fit for the resonance which ultimately
limits the rotor velocity.
the motion of the rotor, but instead monitors the vibrations which are transmitted
to the chamber. This is done by rigidly mounting an accelerometer chip to the top
of the vacuum chamber. While an externally mounted accelerometer cannot measure
the amplitude of vibrations on the rotor, or determine the mode of vibration, it does
have the advantage of detecting vibrational modes the laser is insensitive to. The
experiment is set up to monitor the level of vibration measured by the laser and
the accelerometer, and automatically spins down the rotor if the vibrations grow too
large.
The vibrations observed using these detection systems are significantly larger
than anticipated when the rotor was designed. A plot of vibrational amplitude for
different rotation speeds is shown in figure 3.11. The plot shows the vibrational ampli-
tude measured by the laser in red, and the amplitude measured by the accelerometer
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