Experiments with Supersonic Beams as a Source of Cold Atoms
Experiments with Supersonic Beams as a Source of Cold Atoms
Experiments with Supersonic Beams as a Source of Cold Atoms
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Magnetic flux density [arb. units]<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
280 320 360 400 440 480<br />
Time [s]<br />
Figure 4.13: A temporal pr<strong>of</strong>ile <strong>of</strong> the magnetic field in the center <strong>of</strong> the slowing coil.<br />
The trace is a numerical integration <strong>of</strong> the current induced in a pickup coil placed in<br />
the center <strong>of</strong> the slowing coil.<br />
current in the coil reached its peak value after 35 μs, the field does not reach its peak<br />
for another 5 − 10 μs. Also, while the current shuts <strong>of</strong>f <strong>with</strong>in 7 μs, the field drops<br />
linearly over this time to 35% <strong>of</strong> its peak but decays exponentially from there <strong>with</strong> a<br />
time constant <strong>of</strong> 11 μs.<br />
4.4.4 18 Stage Apparatus and Vacuum Chamber<br />
To make the coilgun work correctly, the coils must be held in alignment in<br />
vacuum. The coils are held in copper discs by vented screws. The copper discs have<br />
three holes drilled into them, and this is how the entire <strong>as</strong>sembly is held together<br />
and aligned. The discs are slid onto three stainless steel rods, <strong>with</strong> stainless steel<br />
spacers between each copper disc. This produces a center to center spacing between<br />
each coil <strong>of</strong> 1.41 cm. Instead <strong>of</strong> spacers, a stainless steel post is used on two <strong>of</strong> the<br />
rods between coils 7 and 8, and between coils 13 and 14. These posts are mounted<br />
in a stainless steel block that is secured by set screws in the vacuum chamber. The<br />
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