Experiments with Supersonic Beams as a Source of Cold Atoms

Figure 3.17: The calculated velocity of the reflected beam plotted against the velocity
of the crystal. The red line is the least square fit of the data, while the black line
shows the expected velocity dependence from simulation.
velocity is calculated from the arrival time of the beam and from the beam path length
calculated from the nozzle to the rotor and from the rotor to the detector. This path
length depends on the phase of the rotor, and is calculated from the nozzle delay
time used to optimize the reflected beam signal. The beam velocities are calculated
by performing a Gaussian fit of the data for each individual nozzle pulse. The mean
of the center of the Gaussian fits is taken as the arrival time, while the standard
deviation of the centers is used to calculate the error.
The red line shown in figure 3.17 is the least square fit of the data, while the
black line is the velocity dependence predicted by simulation. While the dependence
expected from simulation lies within the error bars for the measurement, there seems
to be a real difference in the slope of the two lines. This is most likely a result of the
manner in which the optimal nozzle delay is found. Since the distance between the
reflection point and the detector is short compared with the total travel distance, the
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