Slow ‘thermal’ and fast ‘streamer-leader’ breakdown modes in conductive water

A parametric study of an underwater pulsed plasma discharge in pin-to-pin electrode configuration has been performed. The influence of two parameters has been reported, the water conductivity (from 50 to 500 µS/cm) and the applied voltage (from 6 to 16 kV). Two complementary diagnostics, time resolved refractive index-based techniques and electrical measurements have been performed in order to study the discharge propagation and breakdown phenomena in water according to the two parameters. A single high voltage of duration between 100 µS and 1 ms is applied between two 100 µm diameter platinum tips separated by 2 mm and immersed in the aqueous solution. This work, which provides valuable complementary results of paper [1], is of great interest to better understand the mechanisms of initiation and propagation of pin-to-pin discharge in water. For low conductivity (from 50 to 100 µS/cm) results have confirmed two regimes of discharge (cathode and anode) and the increase of the applied voltage first makes the breakdown more achievable and then favors the apparition of the anode regime. For 500 µS/cm results have highlighted cathode regime for low applied voltage but a mixed regime (anode and cathode) for high applied voltage.

Section: Influence Of the Applied Voltagesupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of applied voltage and electrical conductivity on underwater pin-to-pin pulsed discharge

Rond¹,

Desse²,

Fagnon³

et al. 2018

“…experimental conditions [8,9]. Meanwhile, vaporization and ionization development in the gas phase make it more difficult to explore the mechanisms of discharges [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Experimental observations and interpretations of bubble-induced discharges under microsecond pulsed voltages in water

Wen

et al. 2020

This paper presents experimental investigations on the formation, propagation and termination of bubble-induced discharges in deionized water. Time-resolved visualization and electrical measurements are performed to investigate bubble deformation behaviour and ionization development. The distribution of delay in bubble formation indicates that bubble formation can be categorized into two classes, explained by pre-existing microbubbles and Joule heating, respectively. The weak luminance in bubbles suggests the initiation of ionization, which is verified by calculation of the ionization coefficient. The influence of the charges deposited on the bubble surface on the evolution of bubble morphology and luminance is investigated with time-resolved imaging methods. Observations of strong light emission at the falling edge of voltage as well as termination of the discharges are reported, and the underlying mechanisms are discussed.

“…Plasma discharges in the liquids were further studied by Lebedev and Averin [26], who applied microwave discharges in crude oil at atmospheric pressure in order to separate metals (Al, Co, Cu, Fe, Mo, Ni, V, and Zn). Panov et al [27] studied the slow 'thermal' (with the average speed of plasma channel propagation of 5 m s −1 ) and fast 'streamer-leader' (up to 7 km s −1 ) breakdown modes in conductive water at conductivity of 90 μS cm −1 in the range of applied voltage from 9 to 27 kV in 1 cm gap with pin anode. Finally, Pongrac et al [28] characterized time-resolved emission spectra of Hα/O I atomic lines generated by nanosecond pulsed corona-like discharge ignited by fast rise-time high-voltage pulses (duration 6 ns and amplitude + 100 kV) in a point-to-plane electrode geometry submerged in deionized water.…”

mentioning

confidence: 99%

Special issue on recent developments in plasma sources and new plasma regimes

Akishev

Machala

Koval

2019

With great enthusiasm we present this special issue of Journal of Physics D: Applied Physics, which collects the best selection of the recent state-of-the-art in experimental and numerical research of non-thermal plasma sources and discharge regimes and their wide application possibilities. The research achievements and generation of such plasma discharges promote the advances in many areas of science and technology and open or stimulate new horizons and possibilities for their uses. The issue presents a wide spectrum of new approaches for pulsed generation of plasmas by the ultra-high electric field of nanosecond/ sub-nanosecond duration, formation of discharges with runaway electrons, and generation of plasma by electromagnetic beams from microwave to terahertz diapason. New plasma regimes that were created by various plasma jets and multi-jets, dielectric barrier or other kinds of gas discharges operating in gases, as well as discharges interacting with or directly in liquids are also extensively addressed. Several contributions include modeling of some of these new plasma regimes, and most of them provide examples of applications that benefit from these plasma source designs, with a special focus on biomedical, agricultural, combustion, environmental, nanoparticle and diamond synthesis, and other emerging applications. The special issue is launched with a topical review on low pressure discharges with hollow cathode and anode and their applications, by Korolev and Koval [1]. As historically plasma science started with low pressure electrical discharges and recently the focus moved to atmospheric pressure with a large variety of new applications, reviewing low pressure discharges with extremely small neutral particle density and electron free path in excess of the size of the discharge gap, where the discharge regimes are between the avalanche ioniz ation and pure vacuum discharge in the cathode metal vapors, is still timely. New approaches to the interpretation of the discharge formation mechanism and sustaining are discussed and offer the possibility to obtain a uniform plasma in a large volume of the cathode or anode cavity, in the sources of electron and ion beams based on the plasma cathode and in the high-current pseudospark switches. Several research papers in the issue deal with recent developments and new plasma regimes under low pressures. Burdovitsin et al [2] investigated the beam-plasma formed by an energetic electron beam at fore-vacuum pressure (1-10 Pa range). The maximum plasma density at the optimum collector potential can be much greater than the plasma density when the collector is at ground or at floating potential. Bokhan et al [3] studied an open discharge with counter-propagating electron beams applicable in high voltage pulsed switches with a sub-nanosecond leading edge (kivotrons). It was shown that a fast current development arises when the discharge self-sustaining mode is caused by the photoemission from the cathodes due to the resonant radiation emitted by fast helium atoms with a...