Streamer dynamics and periodical discharge regime transitions under repetitive nanosecond pulses with airflow

Abstract

Although the nanosecond repetitively pulsed (NRP) discharge normally stabilizes into one of three regimes (corona/glow/spark) in a pulse train, another nonintuitive instability recently proved that it could periodically swing between corona and spark regimes characterized by repeated spark quenches and reestablishments (Zhao Z et al 2022 Plasma Sources Sci. Technol. 31 045005). In this paper, we have further investigated the suitability of NRP discharge regime transitions for different pulsed power supplies and revealed dramatic effects of the gas flow on streamer dynamics that possibly lead to spark quenches. Pulse-sequence and temporally resolved electrical and optical diagnostics were implemented to capture discharge evolutions in long pulse trains. Periodical discharge regime transitions under long-term repetitive nanosecond pulses are prevalent under transmission line transformer pulser and commercially available FID pulser with parameter constraints. A minimum deposited energy per spark is required for the successive spark pattern. The spark channel before its quench statistically prefers to deviate upstream rather than following the straight axis or intuitively bending downstream to search for more remnants. Before spark quenches, the initial streamer already either exhibits a large radial “detour” or propagates with a zig-zag profile along the periphery of previous spark regions. The periodical discharge regime transition and effects of the gas flow are qualitatively explained based on the plasma-source coupling, evolutions of dominant negative ions composition, and 3D streamer simulation. Periodical NRP spark quenches are probably initiated with the streamer “detour” and then accelerated by the thermal-ionization feedback instability. Inhomogeneous residual charge distribution and accumulations of complex negative ions with high electron bound energies may facilitate the following discharge to search for the gas inlet. In-depth understanding of NRP discharge instabilities could be reached, which are fundamentally governed by residual charge transport and energy relaxation.

Evolutions of streamer dynamics and discharge instabilities under repetitive pulses in humid air

“…Figure 1 schematically illustrates the experiment setup for repetitively pulsed streamer discharges in the dry and humid air. Electrical and optical diagnostics have been described in detail in our previous studies [18]. Pulsed high voltage and loop currents were measured by a commercially available voltage probe (Northstar Corp., PVM-5) and a current sensor (Pearson, Model 6585, 250 MHz), respectively.…”

“…The gas humidity, either from the water vapor concentration in the surrounding air [12,13] or intentionally supplemented in the gas inlet [14,15], is an important factor for the plasma chemistry [16,17]. On the other hand, streamer discharge evolutions under high-frequency repetitive pulses are more complicated than the conventional double-pulse test [18][19][20], e.g. the progressive spark formation [7], and periodical discharge regime transitions [18].…”

“…On the other hand, streamer discharge evolutions under high-frequency repetitive pulses are more complicated than the conventional double-pulse test [18][19][20], e.g. the progressive spark formation [7], and periodical discharge regime transitions [18]. Discharge memory effects are generic concepts, however, relative contributions from different memory effect agents (residual charge, surplus heat, etc) are difficult to be quantitively determined [21].…”

Effects of DC bias on evolutions of repetitively pulsed streamer discharge in humid air

“…The pulse-periodic streamer discharge is an attractive and convenient method to generate low-temperature plasmas with significant advantages of high electron temperature, high chemically active particle yield [1,2], enabling novel applications in medical sterilization [3], flow control [4] and CH 4 conversion [5]. Characteristics of repetitively pulsed streamer discharges are inevitably affected by various environmental conditions [6][7][8], among which the air humidity is an important factor. On the one hand, the three-body electron attachments are accelerated and chemical reaction maps are more complicated in humid air [9,10].…”

Double-pulse streamer simulations for varying interpulse times in air

“…Furthermore, streamer memory effects and discharge mode transitions due to repetitive pulses have been studied in a series of papers by Zhao et al, see e.g. [19,20], and reviewed in [21].…”