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Home > About us > Media > Archived news > 2022 > Surface charging memory effect demonstrated in pulsed helium plasma jet-target interaction

Surface charging memory effect demonstrated in pulsed helium plasma jet-target interaction

The existence of memory effects, i.e. leftover charges and reactive species that influence subsequent discharges, has long been assumed to have a crucial importance in the operation of DBDs. Memory effects can be present in the gas phase volume or on dielectric surfaces. In this work, a surface charging memory effect is demonstrated and quantified, by both directly measuring and simulating the spatial distribution of electric field inside a dielectric target impinged by pulsed helium plasma jets of different polarities. The diagnostic and the model have been developed at LPP, and this work has been performed in collaboration with Masaryk University, Czech Republic, The University of Liverpool, United Kingdom and the Eindhoven University of Technology, The Netherlands.

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Figure 1
Experimentally-obtained imaging of light emission at different instants during discharge propagation and interaction with a dielectric BSO target, for a pulse of 1 µs length and -5 kV amplitude. The horizontal dashed line (distance=0) corresponds to the end of the dielectric tube. The target is placed at a 10 mm distance. Besides the ionization wave propagating towards the target, a discharge is ignited on the target surface and a reconnection between the two discharges takes place.

The examined memory effect consists in a significant amount of surface charges and electric field remaining in the target in between discharge pulses (200 μs off-time). The memory effect is especially important when using negative electric polarity. In that case, counter-intuitively, the target remains positively charged in between pulses. This is shown to directly impact the ionization wave dynamics, as the surface charges lead to the ignition of a second discharge on top of the target as the ionization wave approaches it. The reasons for the lack of target neutralization and the remainder of surface charges are investigated.

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Figure 2
Radial profiles at different instants of the axial component of electric field inside a dielectric BSO target (Ezav, solid lines) from simulations and measurements, and of the simulated surface charge density (σ, dashed lines) on the target surface, for the same pulse of applied voltage as in figure 1. t refers to the instant in time in experiments and ts to the instant in time in simulations. Positive Ezav and σ remain in the target in between pulses.

Contacts at LPP: Olivier Guaitella and Anne Bourdon – Low-temperature Plasma Group

Source:
P. Viegas, E. Slikboer, Z. Bonaventura, E. Garcia-Caurel, O. Guaitella, A. Sobota and A. Bourdon
Quantification of surface charging memory effect in ionization wave dynamics
Scientific Reports 12, 1181 (2022)
https://doi.org/10.1038/s41598-022-04914-8


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