The plasma opening switch (POS) is used in pulsed power systems where a very fast opening
and high current switch is required. Plasma is injected into the switch, which carries a large
conduction current, before it opens in a process that lasts for a few nanosecond and transfers
the current to a parallel-connected load at a much increased voltage and with a much shorter
rise time. The conduction and opening times of the switch are dependent on plasma
parameters such as the distribution, speed and species, all of which are determined by the
Most of the earlier reported work involves large dimension POSs and a correspondingly high
input current (more than 100 kA) and uses carbon plasma. One main objective of the present
research was to achieve a low input current (20 kA) and miniaturised POS by using hydrogen
plasma rather than carbon plasma on account of its lower mass.
A cable gun was selected for producing the plasma, since although this produces both
hydrogen and carbon plasma these arise different times during its operation.
For the present application a Tesla transformer was used in preference to a Marx generator to
produce an initial high voltage pulse for the system, on the basis of its simpler design and cost
effectiveness. This transformer together with an associated water PFL (pulse forming line)
and pressurised switch was capable of producing a load current in excess of 20 kA with a rise
time of 53 ns, which was fed through the POS to the final load.
Special diagnostics arrangements were necessary to measure the fast high current and voltage
pulse a in nonintrusive way. Faraday cups and a high speed camera were used to measure the
The overall system built (i.e. including the POS) is capable of producing a 22 kA current with
a rise time of 5 ns, and of generating a power of more than 10 GW.
Much of the work detailed in the thesis has already been presented in peer reviewed journals
and at prestigious international conferences.
A Doctoral Thesis submitted in partial fulfilment of the requirement for the award of Doctor of Philosophy of Loughborough University, U.K.