Simultaneity of Spark Gap Switch Firing in the Dense Plasma Focus Device

Abstract

To gain insight into the synchronization, simultaneity, and switching behavior of the individual switch, two TIA-525 Optical/Electrical converters have been recently introduced to DPF experiments at Lawrenceville Plasma Physics (LPP). These electronic devices, attached to two spark gap switches through optical fibers, detect light sampled from the switch firing and convert it to amplified voltage signals. We observed that in terms of simultaneity and synchronization, the firing behavior and quality of the pair of switches monitored are not the same. Some switches, among the twelve that are being used, fired at the trigger voltage within few tens of ns while the others fired much later (after ~1–2 μs) and are triggered at or after the pinch voltage rise. The results from the present work show evidence of pinch voltage triggering the switches. Since the pinch voltage is over three times the voltage of the capacitors, this voltage triggers those capacitors that do not fire during the regular high voltage trigger pulse. This, we suggest, could affect the efficiency of the device as it simply drains the reserved energy in the system. We present results of an empirical study of spark gap switch firing as well as the total current that is followed using the Rogowski coil.