Pulsed electrical discharge in conductive solution

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

“…The experiments are performed in inhomogeneous electric field provided by 'pin-to-rod' electrode geometry (figure 1), with the pin being positive. All the experimental apparatus are the same as in [13]. Recalling the most important parameters, the anode has a conic shape with tip radius of 100 µm, the rod-cathode is 2 mm in diameter and has a flat rounded tip, the voltage pulse is positive polarity, rise time is 0.4 µS, full width at half magnitude is 3 ms, discharge current is limited by ballast resistance R b = 5.5 kΩ.…”

“…Previous experimental data on 'thermal' breakdown development are very limited [11] and do not provide any detailed explanation on the underlying physics except for some initial stages [12]. The physics and dynamic of 'thermal' breakdown in conductive water in inhomogeneous electric field have been studied recently in [13] for tap water (300 µS cm −1 ).…”

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

“…The collision ionization coefficient, α, is a key parameter for estimating the initiation of impact ionization. Previously, α in the bubble was usually calculated using the Townsend equation [28,29], in which parameters are selected to be the same as in air. This will inevitably cause a deviation when we apply it directly to a water vapour bubble.…”

“…These atmospheric bubbles could provide suitable conditions for streamer development. Nevertheless, the bubbles induced by pulsed discharges have a much smaller radius (∼10-100 µm [23]) and higher pressure (3-4 bar [28]) than the injected bubbles, which will suppress streamer initiation and deserves further investigation.…”

“…With regard to the mechanisms for ionization development in bubbles, a rough estimation of the ionization coefficient based on the Townsend expression has been calculated to determine whether electrons can trigger electron avalanches in bubbles [28,29]. The criterion calculation adopts the data for breakdown in air, which do not properly describe the ionization process in water vapour.…”