A new study improves our understanding of plasma¹ 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 physicists² from the University of Greifswald, Germany, Robert Wild and Lars Stollenwerk, and are about to be published in EPJ D. Under certain circumstances, plasma tends to form structures such as filaments⁴（花丝，细丝） of electric discharge akin⁵ 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 filament³ pattern, which is arranged hexagonally, to a disordered system due to the reduction of the externally applied⁶ 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 spatial⁷ patterns（空间格局）, called 2D Fourier transformation⁸. Then, for the first time, they applied an analysis tool typically used to evaluate dusty plasma discharges, known as triple correlation⁹ 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 pivot¹⁰ point（枢轴点） 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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