Experiments with Supersonic Beams as a Source of Cold Atoms

250V
1MΩ
3x 2.2mF
TTL 5V
feedback
controller
10μH
.15Ω
.25Ω
N Channels
4Ω
2x 2μF
Figure 5.4: A schematic of the hydrogen coilgun coil switching circuit. Each coil has
its own IGBT. The only shared circuitry is the power supply circuit which charges the
capacitors. This change eliminates the need for a thyristor, and is feasible because
only 18 coils are required to slow hydrogen, reducing the cost of not sharing IGBTs.
of the previous 7 μH). In addition, the effective resistance of the coil is significantly
reduced due to the increased wire size and the lack of vacuum feedthroughs. Since
the magnetic moment to mass ratio of hydrogen is so high, only 18 coilgun coils
are needed, reducing the need to switch multiple channels with the same circuitry.
Finally, the current being run in the coil has increased from 750 A to 825 A. All of
these changes result in the need to tune the switching circuit to better suit the needs
of the hydrogen specific coilgun.
A schematic of the modified switching circuit can be seen in figure 5.4 and
a photograph of the circuit can be seen in figure 5.5. This circuit differs from that
described in sections 4.4.3 and 4.5.2 in several ways, though the overall form remains
broadly similar. The largest change from the previous circuits is the removal of the
thyristor. This significantly increases the reliability of the circuit, as the thyristors
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