Final Implementation of a Subnanosecond Rise Time, Variable Pulse Duration, Variable Amplitude, Repetitive, High-Voltage Pulse Source

In this paper, we present the final implementation of our 0-50-kV picosecond rise time 0.5-10-ns pulse generator. The pulse generator will be used in future work to generate a (sub)-nanosecond streamer plasma for air purification research. The pulse generator is a single-line pulse generator with an oil spark-gap (SG), which generates 0.5-10-ns pulses with a 200-ps rise time and can operate at repetition rates of over 1 kHz into a 50-Ω load. It is an improvement over the first implementation of our nanosecond pulse generator that we designed and verified experimentally in previous work. In this paper, we evaluate the performance of the final design. Furthermore, we present 3-D electromagnetic simulations of the nanosecond pulse generator and show that the simulations are in good agreement with the measurements. A variation in pulse duration from 0.5 to 10 ns is possible and the output pulses are square shaped without the large plateau behind the main pulse that was present in the pulses from the first implementation of the nanosecond pulse generator. At high voltages, the pulse top becomes less flat due to a time-dependent mismatch in the spark-gap. Furthermore, investigation of electrode erosion of the oil spark-gap shows that the erosion rate of the electrodes is in the range of 200-600 μcm³ · C^-1 for the electrode that is mainly the cathode and 100-300 μcm³ ·C^-1 for the electrode that is mainly the anode, respectively. This is almost an order of magnitude higher than most gas spark-gap studies show for brass electrodes. Therefore, electrode erosion in the oil spark-gap will be a limiting factor on the lifetime of the system. We designed a new electrode with a stainless steel head to increase this lifetime.