Nanosecond pulsed streamer discharges Part I:Generation, source-plasma interaction and energy-efficiency optimization

\u3cp\u3eStreamer discharges generated by nanosecond high-voltage pulses have gained attraction for a variety of reasons, but mainly because they are very efficient for a number of plasma-processing applications. More specifically, researchers have noted that the pulse duration and the rise time of the applied high-voltage pulse have a significant influence on the radical yield of the transient plasmas generated with these pulses; shorter pulses result in higher yields. With the need to study transient plasmas generated by these short pulses comes the need to understand how to generate those pulses and to understand the interaction between the pulse source and the discharge. In this topical review, we will explore the different methods with which to generate nanosecond high-voltage pulses, how the interaction between the pulse source and the discharge may influence the source and the discharge and how to optimize the energy transfer from the pulse source to the discharge.\u3c/p\u3

Direct comparison of pulsed spark discharges in air and water by synchronized electrical and optical diagnostics

In this study, a direct comparison was made between pulsed spark discharges in air and water in sub-mm gaps. The discharges were ignited at atmospheric pressure in the same discharge arrangement for air and water, using a solid-state microsecond pulse source with ≈1 μs voltage rise time (Umax up to 37 kV). Fast voltage and current measurements were synchronized with iCCD imaging with high spatial resolution on symmetrical half-sphere tungsten electrodes (electrode gaps of up to 0.7 mm for air and 0.3 mm for water). The breakdown voltage and electrical field strength, maximal current, transferred charge, consumed electrical energy and discharge emission structure (e.g. discharge channel diameters) was obtained for all cases. Using the synchronization of the electrical data and the iCCD imaging, current and energy densities were estimated for the sparks in air and water. It was found that the breakdown voltage, the discharge current, the transferred charge, and the consumed electrical energy increase with the gap distance, and that this dependency is much stronger for discharges in water (compared to air). Due to the use of the same discharge arrangement and the same applied voltage, the difference in the discharge characteristics was directly quantified. Graphical abstract: [Figure not available: see fulltext.]

Fast pulsed power generation with a solid-state impedance-matched Marx generator: concept, design, and first implementation

In this article, we present the concept, design, and first implementation of a new solid-state pulse topology: the solid-state impedance-matched Marx generator (IMG). This new topology can bring fast, adjustable pulse generation to a wide range of pulsed power applications. Where the original IMG is a high-power device (using spark gaps) for relatively low-repetition-rate, high-energy-density physics, we require a pulse source with a (sub)nanosecond rise time at moderate voltages of tens of kilovolts at high repetition rates for transient plasma generation. To achieve this, we adapted the IMG pulse source concept to a solid-state concept with additional transmission lines and metal-oxide-semiconductor field-effect transistor (MOSFET) switches. In this article, we present the general concept, a 20-stage design (with 3-D transient electromagnetic simulations), and a first 5-stage, 5-kV prototype. The prototype achieves 5-6-ns rise time pulses at voltages up to 2.5 kV into a matched 50- \Omega load (due to an oscillation in the drive circuit, the pulse was somewhat distorted at higher voltages) and can generate flexible pulse waveforms. Finally, improvements are suggested to achieve the desired pulse specifications

15-Stage compact Marx generator using 2N5551 avalanche transistors

\u3cp\u3eIn this contribution, we present a 15-stage, avalanche transistor Marx generator using inexpensive 2N5551 transistors. It can be used in low-power biomedical, environmental and food applications where compact circuits to generate high-voltage pulses are required. We characterized the avalanche transistors and built a test setup with 15 stages which provides 1.3-kV pulses into a 50 Ohm load and over 3-kV into a small capacitive load (such as a small plasma reactor). Furthermore, by optimizing placement of starting capacitances, the rise time of the circuit could be adjusted to just under 2 ns, which can still be further optimized.\u3c/p\u3

Fast pulsed power generation with a solid-state impedance-matched Marx generator:concept, design, and first implementation

\u3cp\u3eIn this article, we present the concept, design, and first implementation of a new solid-state pulse topology: the solid-state impedance-matched Marx generator (IMG). This new topology can bring fast, adjustable pulse generation to a wide range of pulsed power applications. Where the original IMG is a high-power device (using spark gaps) for relatively low-repetition-rate, high-energy-density physics, we require a pulse source with a (sub)nanosecond rise time at moderate voltages of tens of kilovolts at high repetition rates for transient plasma generation. To achieve this, we adapted the IMG pulse source concept to a solid-state concept with additional transmission lines and metal-oxide-semiconductor field-effect transistor (MOSFET) switches. In this article, we present the general concept, a 20-stage design (with 3-D transient electromagnetic simulations), and a first 5-stage, 5-kV prototype. The prototype achieves 5-6-ns rise time pulses at voltages up to 2.5 kV into a matched 50- \Omega load (due to an oscillation in the drive circuit, the pulse was somewhat distorted at higher voltages) and can generate flexible pulse waveforms. Finally, improvements are suggested to achieve the desired pulse specifications.\u3c/p\u3

Fast and Flexible, Arbitrary Waveform, 20-kV, Solid-State, Impedance-matched Marx Generator

We developed a new pulsed power supply to study the influence of the high-voltage (HV) pulse shape on the generation of plasma-activated water (PAW). This article shows the design and implementation of the generator and evaluates its performance on resistive loads. The design is an improved version of the solid-state impedance-matched Marx generator (SS-IMG) concept as previously developed at Eindhoven University of Technology. The IMG concept allows for sub-nanosecond rise time pulses, to be able to create a nonthermal plasma very efficiently. A conventional SS-Marx generator (SS-Marx) circuit is taken as the starting point, and a careful implementation is made with most electrical connections analyzed as transmission lines (TLs). All these TLs are impedance-matched to each other and the load. The implemented generator is able to generate 25 ns to μ s duration pulses of 20 kV up to 10-kHz repetition rate in a 50- Ω load with about 8 ns rise time and arbitrary pulse shape. Future improvements are suggested which will increase the repetition rate and decrease the pulse rise time to the sub-nanosecond regime