Using a laser-ablation plasma to model the operation of a lightning rod in the lab

Abstract

We report results obtained in a point-plane impulse discharge experiment in the presence of a pre-existing ablation plasma. The ablation plasma is created by focusing a high power, pulsed laser on the surface of the plane electrode prior to the application of the impulse discharge. We posit that this plasma can act as a miniature lightning rod in lab-scale experiments. It was found, for example, that under negative polarity and 50 mJ laser energy the ablation plasma successfully attached around 51% of the discharges. However, inversion of the polarity, keeping the laser energy fixed, produced a meagre ~4% attachment rate. It was also found that too much laser energy can have a deleterious effect on the attachment rate: for example, increasing the energy from 50 to 200 mJ/pulse produces a decrement of 29% in the rate. The results obtained can also improve the understanding of how early-streamer emission protection systems operate. As with full-size lightning rods, we observed a protected zone near the ablation plasma with almost zero impacts. This result was used to test the scalability of the rolling-sphere model.