Particle-in-Cell Simulation on Spark Gap

Spark gap is a fundamental switch in pulsed power system, its physics are well known and spark gaps capable of tens of kA are available commercially. Spark gap is easy to manufacture, traditional method is by try and error to estimate the self-breakdown voltage between the anode-cathode gap according to Paschen's law, and then adjust the air pressure accordingly. However, simulation of spark gap is less seen. In this article we try to simulate the physics and behavior in spark gap using a particle-in-cell code. A set of electrodes is setup as anode and cathode, and a pulsed high voltage is sent via transmission line to the cathode. When the field between cathode and anode exceeds the explosive field emission threshold, seed electrons are emitted from the emission sites, and then impact ionization in gas takes over, and eventually the voltage on anode changes when the electrons arrive. The value of such simulation is that if spark gap can be simulated, then an entire pulsed power system can be simulated, including pulse forming line connected to a spark gap and then to a high power microwave source, all in one simulation.