Generation of fast-rise time, repetitive, (sub) nanosecond, high-voltage pulses

In this contribution we present our fast-rise time nanosecond pulse generator, capable of generating up to 50 kV (positive and negative) rectangular pulses at a repetition rate of up to 1 kHz and with a rise time of less than 200 picoseconds. We focus on the general concepts involved in the design of this pulse source, with special attention to the basic underlying principles and the key characteristics that make it operate.
The pulse source is based on the classic single-line pulse forming line topology, which is capable of producing rectangular pulses, the duration of which is determined by the properties of the pulse forming line. Furthermore, by changing these properties of the pulse forming line, and by varying the charging voltage of the line, we can flexibly change the pulse duration from 0.5 to 10 nanoseconds and the amplitude from -50 kV to 50 kV, while the rise time of less than 200 picoseconds is maintained.
Special attention is paid to the switch that is used to discharge the pulse forming line into the load of the pulse source. In our case, we used an oil-spark gap for this switch to ensure extremely fast, low-inductance switching. In addition, the impedance of this switch was carefully matched to the rest of the system to prevent pulse reflections. This consideration, together with the careful design of the pulse forming line, allows the pulses to be rectangular with minimal deformation.
A final design consideration is the connection of the pulse source to the load. Ideally, all energy from the pulse source is consumed by the load, which can only occur when the matching of the load to the pulse source is optimized. As an example, we will present experiments with different designs for a non-thermal plasma load that can achieve high energy transfer from the pulse source to the load.
Applications for the pulse source can be found in environmental studies (e.g. generation of non-thermal plasma for pollution control, ozone generation, etc.) and bioelectrics. We will present data on pollution control studies with a corona-streamer plasma that show excellent yields when using the nanosecond pulse source.