Resistance of Spark Channels

A study undertaken to measure the resistance of spark channels in air with two different current waveforms is presented. In one experiment, the spark was created by a Marx generator. In this case, the gap length was maintained at 12.8 cm, and the current flowing through the spark had a peak current lying in the range of 0.2-2.2 kA. The decay time of the current was larger than 100 mus. In the other experiment, the spark was created by a current generator. In that experiment, the gap length was maintained at 1 cm, and the current flowing through the spark had peak-current amplitudes in the range of 35-48 kA. The decay time of the current was larger than 500 mus. The results show that the resistance of spark channels initially decreases, reaches a minimum value, and then recovers as the current in the spark gap decreases. The minimum resistance of the spark channel decreases with an increasing peak current. The results are compared with various theories that attempt to predict the temporal variation of the resistance of spark channels. The comparison shows that further developments in the existing theoretical models are needed in order to reproduce with better accuracy the dynamic behavior of the channel resistance