A new study improves our understanding of plasma sources, a state of matter similar to gas in which a certain portion of the particles are ionised and which are used for example in plasma display panels. These results revealed by physicists from the University of Greifswald, Germany, Robert Wild and Lars Stollenwerk, and are about to be published in the European Physical Journal D.
Under certain circumstances, plasma tends to form structures such as filaments of electric discharge akin to mini-lightning. The authors specifically investigated a so-called barrier discharge, which features at least one electrical insulating material within the discharge gap that acts as an electrically insulating barrier and can be used as a plasma source.
They investigated the transition from a highly ordered filament pattern, which is arranged hexagonally, to a disordered system due to the reduction of the externally applied voltage.
To analyse the transition in the order of the discharge, Wild and Stollenwerk used two approaches. First, they used a method commonly employed to analyse spatial patterns, called 2D Fourier transformation. Then, for the first time, they applied an analysis tool typically used to evaluate dusty plasma discharges, known as triple correlation function. The latter approach offers the advantage of considering only the positions of the nearest neighbouring filaments and of disregarding their actual geometry. As a consequence, it is used to estimate the probability of finding a second filament at a certain angle and distance from a first filament.
The authors observed a pivot point in the voltage at which the decaying order started occurring. This information can ultimately be used to guarantee the quality of applications such as plasma screens. That is because the dissolution of self-organised electric discharge filaments in plasma matter enhances the homogeneity of the matter.
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R. Wild, L. Stollenwerk (2012), Breakdown of order in a self-organised barrier discharge, European Physical Journal D; DOI 10.1140/epjd/e2012-30220-4