Initial results from precision spark resistance measurements

Understanding variations in time of the resistance of spark channels is not only key to comprehend gas discharges but also in the application of electrical sparks as ultrafast switches. Although previous work has been done to measure the time scale for collapse of the spark gap resistance, and the resistance recovery in the established spark channel [Cernak et al. JPD, 1995; Larsson, JPD, 1998; Montano et al., IEEE TPS, 2006]; experimental data on this topic remains scarce. In an effort to gain insight into natural lightning behaviors (particularly of streamers and leaders) from laboratory tests, we are constructing a Spark Lab at New Mexico Tech. Our initial apparatus is confined to 100 kV gap voltage, but allows us to control spark timing with an average of only 7 ns jitter averaged over 50 triggers. This will be helpful for developing diagnostic instrumentation both for laboratory discharges and natural lightning. In this preliminary investigation, we present effective resistance measurements of the spark channels from spark gaps between 2 and 10 cm, with high temporal resolution.