Marx Generator
The Marx generator is similar to the Cockcroft-Walton
voltage multiplier in that it charges a number of capacitors in parallel
and then discharges them in series. Likewise, the output voltage
is the stage voltage multiplied by the number of stages. However,
where the C-W uses diodes to achieve rapid switching of the supply and
output currents, the Marx generator uses a combination of chokes or resistors
to charge the capacitors and spark gaps to discharge them. The spark
gaps, when triggered, or over-voltaged, connect the capacitors together
in series, allowing the stored potentials to add together to provide very
large outputs. The chokes, or resistors, connect the charging supply
to the capacitors, but limit the capacitor's discharge rate during spark
gap conduction. In order for the Marx generator to function, the
spark gaps must all fire in less time than it would take for any single
capacitor to discharge through it's chokes. Fortunately, spark gaps
typically reach maximum conductance in about 10 nanoseconds.
This is a schematic for a five stage Marx generator
using chokes. In this case the total, or erected, capacitance of
the generator would be 1/5 of the individual stage capacitances.