This paper is devoted to the study of the argon flow modification in a cold atmospheric pressure plasma jet driven by nanosecond high voltage (HV) pulses, from single to multiple HV shots applications.
Helium electric charge free#
In the free APPJ (with no target), on the voltage falling edge, a negative electric field drives the electron flow to compensate the positive ions left over during the forward IW propagation on the voltage rising edge. However, with a dielectric target, the residual surface charges generate a background electric field in the opposite direction to that during IW propagation. With a metal target, no residual electric field is observed before imposing the high‐voltage pulses. The effect of target conditions on the IWs in APPJs is also explored. As for the temporal Ez trend, there is a mode transition from the single‐peak feature under a low peak voltage to the double‐peak feature under a higher peak voltage, indicating the existence of both primary and secondary IWs. Especially, the radial distribution of Ez transits from a central peak profile before the IW front arrives to a hollow profile after the pass of the IW front. The movement of the luminous APPJ head is recognized as the development of the IW front, accompanied with the propagation of the peak electric field. Typical ionization waves (IWs) are observed during the propagation of nanosecond pulsed atmospheric pressure plasma jets (APPJs) with argon flow, combining both the measurement of the axial electric field (Ez) and the temporal resolved optical imaging. Finally, open questions and perspectives for the physics of plasma jets and interactions with surfaces are outlined. Focusing on coaxial helium kHz plasma jets powered by rectangular pulses of applied voltage, physical phenomena imposed by different targets on the discharge, such as discharge acceleration, surface spreading, the return stroke and the charge relaxation event, are explained and reviewed. The physics of plasma jets is described for jet systems of increasing complexity, showing the effect of the different components (tube, electrodes, gas mixing in the plume, target) of the jet system on discharge dynamics. This exposure is focused on the most fundamental physical quantities determining discharge dynamics, such as the electric field, the mean electron energy and the electron number density, as well as the charging of targets. The state-of-the-art of numerical models and diagnostic techniques to describe helium jets is presented, along with the benchmarking of different experimental measurements in literature and recent efforts for direct comparisons between simulations and measurements.
This topical review addresses the physics of plasma jets and their interactions with surfaces through a pedagogical approach.
As such, plasma jets provide an ideal testbed for the study of transient reproducible streamer discharge dynamics, particularly in inhomogeneous gaseous mixtures, and of plasma-surface interactions. Plasma jets are sources of repetitive and stable ionization waves, meant for applications where they interact with surfaces of different characteristics.
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