Discharge in air in contact with water: influence of electrical conductivity on the characteristics and the propagation dynamics of the discharge
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Bibliographic record
Abstract
Abstract Due to the high reactivity and the non-thermal properties of streamer discharges, they are applied in various fields, such as water treatment and medicine. Streamer discharges are usually produced in the gas phase before interacting with a liquid or solid surface. Although the dynamics of a streamer discharge in gases is well described, its propagation at liquid surfaces remains poorly understood. In this study, we investigate the influence of water electrical conductivity ( σ ), between 2 and 1000 µ S cm −1 , on the characteristics and propagation dynamics of pulsed positive DC nanosecond discharges with the solution serving as a cathode. σ strongly influences τ r (the dielectric relaxation time), and two discharge modes may be obtained, depending on whether τ r is shorter or longer than the delay to achieve breakdown ( τ pulse ). This latter can be indirectly modified by adjusting the voltage amplitude ( V a ). In the case of V a = 14 kV, the breakdown voltage ( V bd ) at low σ is lower than that measured at high σ , probably because τ pulse < τ r and > τ r , respectively. In the case of V a = 20 kV, V bd decreases slightly with σ , probably because of the decrease of the resistivity of the global electrical circuit as τ pulse ∼ τ r for high σ . In addition to the electrical characterization, the dynamics of the discharge at the solution’s surface is investigated using 1 ns-time-resolved imaging. Its morphology was found to evolve from a disc to a ring before it splits into highly organized plasma dots (streamers’ head). The number ( N dots ) and propagation velocity of plasma dots are determined as a function of σ . At V a = 14 kV, N dots does not vary significantly with σ despite the increase of V bd ; this latter likely compensates the neutralization of charge accumulated at the surface by ions in solution. In the case of V a = 20 kV, N dots decreases with σ , and it can be related to a decrease of accumulated charge at the water surface. Finally, based on the electrical measurements, we found that the charge per plasma dot ( Q dot ) increases with σ , which does not correlate with the imaging results that show a short length of propagation at high σ . Then, considering the plasma dot mobility at low σ and the instantaneous propagation velocities at high σ , a more realistic Q dot is measured.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it