Positive and negative streamers in air and nitrogen in a sharply inhomogeneous electric field under conditions of runaway electron generation

Abstract

The development of positive and negative streamers in a point‐to‐plane gap filled with air and nitrogen at various pressures (50–200 kPa) and voltages (8–25 kV) was studied. A four‐channel intensified charge‐coupled device (ICCD) and a streak‐camera were used. Electrical parameters were measured with high resolution (10 GHz). An original method of measuring a displacement current caused by a streamer was applied. As was expected, positive streamer branches in nitrogen at low voltages and/or elevated pressures while a large‐diameter streamer is formed in air. However, at high voltages or negative polarity, the large‐diameter streamer is formed both in nitrogen and air in the entire pressure range. It was found that runaway electrons (REs) are generated in the very first picoseconds of gas ionisation near the pointed cathode. It was assumed that REs can be generated near the pointed anode and produce bremsstrahlung radiation due to a sharply inhomogeneous distribution of electrical potential. It was found that in the final stage of negative streamer development in air and nitrogen, the gas between the streamer front and the opposite electrode is ionised almost simultaneously in the entire volume when the streamer diameter is almost equal to the interelectrode gap.

Time-resolved investigations of a glow mode impulse dielectric barrier discharge in pure ammonia gas by means of E-FISH diagnostic

“…A pulsed plasma ignition occurs every half-period with T /2 = 125 µs, while the voltage at the upper electrode varies from its highest (+3 kV) to its lowest value (−3 kV), defined as the negative transition NT, and from its lowest (−3 kV) to its highest (+3 kV) value, defined as the positive one PT. The resulting periodic current of these voltage transitions tends to classify this iDBD regime as a homogeneous discharge contrary to a filamentary discharge characterized by a series of intense current strikes [8,12,43,44], as in sine-AC regime. A second temporal aspect concerns the time needed for the voltage to reach its set value, at a transition.…”

Mechanism of plasma chemistry in CO2 hydrogenation using a dielectric barrier discharge reactor

“…During the plasma discharge process, changes in the background temperature may affect many physical properties of the plasma reactors. [29][30][31][32][33][34][35][36][37][38] To determine its contribution to the physical properties, the effect of temperature on the Lissajous graph was investigated in CO 2 /H 2 mixture. Typical Lissajous graphs under different temperatures at U peak = 6 kV and P dis = 10 W are shown in Figure 2.…”

Magnesium Oxide and Magnesium Fluoride Nanopowders Produced in a Diffuse Nanosecond Discharge in Argon

“…The setup consisted of a gas discharge chamber, coaxial transmission line, and generator of high-voltage nanosecond pulses. The gas discharge chamber with the transmission line was primarily developed by us to perform studies on nanosecond discharges and cold plasmas in various gases in a wide pressure range and electrode configuration, both with optical (spectral) methods and through accurate measurements of the electrical parameters [15]. Nevertheless, it can be adapted for obtaining nanoparticles and optimized directly for the task of synthesis.…”