Impact of electrical grounding conditions on plasma–liquid interactions using Thomson scattering on a pulsed argon jet

The interaction between an argon plasma jet excited using microsecond duration voltage pulses and a liquid target was examined using Thomson scattering to quantify the temporal evolution of the electron density and temperature. The electrical resistance between a liquid target and the electrical ground was varied from 1 to $$680\, \text {k}\Omega $$ 680 k Ω to mimic different conductivity liquids while the influence of the varying electrical properties on the electron dynamics within the plasma were examined. It was demonstrated that the interaction between the plasma jet and a liquid target grounded via a high resistance resulted in typical dielectric barrier discharge behaviour, with two discharge events per applied voltage pulse. Under such conditions, the electron density and temperature reached a peak of $$1\cdot 10^{15}\, \text {cm}^{-3}$$ 1 · 10 15 cm - 3 and 3.4 eV, respectively; with both rapidly decaying over several hundreds of nanoseconds. For liquid targets grounded via a low resistance, the jet behaviour transitioned to a DC-like discharge, with a single breakdown event being observed and sustained throughout the duration of each applied voltage pulse. Under such conditions, electron densities of $$2{-}3 \cdot 10^{15}\, \text {cm}^{-3}$$ 2 - 3 · 10 15 cm - 3 were detected for several microseconds. The results demonstrate that the electron dynamics in a pulsed argon plasma jet are extremely sensitive to the electrical characteristics of the target, which in the case of water, can evolve during exposure to the plasma.

PEA Electromagnetic Distortion Reduction by Impedance Grounding and Pulsed Voltage Electrode Configurations

Space charges are one of the main challenges facing the constantly increasing use of extruded high voltage direct current (HVDC) cables. The Pulsed Electro-Acoustic (PEA) method is one of the most common procedures for space charge measurements of insulation. One issue with the PEA method is distortion due to the crosstalk between the applied voltage pulse and the acoustic sensor. This work analyzed two factors involved in the reduction in this distortion: the influence of the exposed semiconductor distance between the injection electrodes and PEA test cell, and the influence of adding a reactance at the grounding circuit of the PEA test cell. The interaction of these two factors with the distortion was analyzed through a series of experimental testing. Moreover, the performance regarding distortion after applying a developed coaxial injection was compared with the standard non-coaxial injection configuration. It was observed that these two factors had a direct impact on distortion and can be utilized for the reduction in distortion arising from the crosstalk of the applied pulsed voltage. The results can be utilized for the consideration of practical aspects during the construction of a PEA test setup for the measurement of full-size HVDC cables.

Effects of tuning the applied voltage pulse periods on the electroluminescence spectra of host–guest white light-emitting electrochemical cells

Tunable correlated color temperature of electroluminescence from white light-emitting electrochemical cells based on adjusting the voltage pulse period.

The Improvement of Machining Accuracy on Quartz and Glasses by Electrochemical Discharge Machining

In the present study, a tungsten rod with diameter of 100μm is used as the tool to drill a quartz plate by Electrochemical Discharge Machining (ECDM). KOH solution mixed with different concentration of Ethanol is used as the electrolyte. The influences of different working parameters, such as electrolyte concentration, applied voltage, pulse frequency, and electrolyte level, on the gas film stability, gas film thickness, and machining accuracy are investigated. The experimental results show that the overcut and surface roughness is improved by the use of electrolyte with addition of 6.5wt% ethanol. The effect of gaseous bubbles is reduced during the machining, and the circulation of electrolyte is better. Compared with machining with pure KOH electrolyte, the overcut is reduced around 57% by the use of electrolyte with addition of 6.5wt% ethanol. The heat-effected zone on the machining is also largely reduced.

Modeling and Experiment of Pulse Electrochemical Deburring on Inclined Exit Surface of Drilling Hole

In this paper the characteristics of pulse electrochemical deburring (PECD) is analyzed through a developed mathematical model and main influencing factors such as applied voltage, pulse duty factor, deburring time, initial burr height and initial interelectrode gap on burr height have been analyzed. The paper also highlights the scheme of the developed PECD system designed to operate within the parametric limits. The calculated results obtained from the mathematical model are found to be approximately consistent with the experimental results. The results show that initial burr height h0=0.057mm is removed, and the fillet radius R=0.248mm is obtained. The present paper through various parametric studies will act as a guideline for the operation of a PECD system.

Freestreaming mode excited by a pulse

When a voltage pulse is applied to an exciter (probe or grid) immersed in a plasma, both an ion-acoustic wave and a freestreaming (ballistic) signal are excited. It is shown that the density perturbation produced by the freestreaming signal is independent of the shape of the applied-voltage pulse for times that are large compared with the temporal width of the pulse and at distances that are large compared with the size of the sheath at the exciter, but it depends on the second derivative of the zeroth-order velocity-distribution function. Analytic expressions that are valid for all times and positions are derived for a simple sheath model. Criteria are presented that enable the experimentalist to distinguish freestreaming modes from ion-acoustic waves.