Title:
Spark gap optimization by electrodynamic simulations
Author(s):
Hendriks, S B van der Geer and G J H Brussaard
Source:
J. Phys. D: Appl. Phys.
Vol./Issue/Date:
Vol. 39
Year:
2006
Page(s):
274–280
Keywords:
Abstract:
When switching times are no longer dominated by the plasma formation
time, such as for photoconductive switching of high-voltage spark gaps,
electrodynamic details of the switching process determine the rise time and
pulse shape of the switched pulse. We show that the commonly used
zero-dimensional lumped element and one-dimensional transmission line
theory are no longer sufficient for optimizing such fast-switching devices,
because important electromagnetic-field propagation in three dimensions is
neglected. In order to improve the output of the photoconductively switched
spark gap, we developed an optimization procedure for spark gap
geometries based on full three-dimensional electrodynamic simulations. By
monitoring the electromagnetic-field propagation in time, it will be shown
that the initial electromagnetic-field disturbance in the gap reflects at the
outer conductor and interferes with the initial field. The reflection and
interference are essential for the shape of the output signal. We propose the
following optimization procedure to improve the output of the
photoconductively switched coaxial spark gap. Initially, the reflection and
interference can be influenced by reshaping the inner conductor. The outer
conductor can be used to fine-tune the system to get an output pulse with a
sharp rising edge and no significant oscillations. We also present the optimal
spark gap geometry that gives the best output signal at photoconductive
switching.
Document:
Reference Id:
59
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