The plasma discharge channel in three-dimensional helical shape induced by pulsed direct current (DC) discharge without external stable magnetic field is discovered experimentally. It can be observed by intensified charge-coupled device camera that a luminous plasma structure fast propagates along a helical path in the form of guided streamer (ionization wave). And the propagation of the streamer is stable and repeatable. We take this streamer which propagates along the helical discharge path as the study object, and explain its mechanism by constructing an electromagnetic model. The result shows that the helical shape plasma plumes can exhibit two different chiral characteristics (right-handed and left-handed helical pattern). While the discharge parameters such as pulse frequency, boundary condition, etc. can all affect the propagating characteristics of helical streamers. The electromagnetic radiation driven by pulsed DC power inside the dielectric tube which forms the wave mode is an important source of the poloidal electrical field. The helical steamers form when the poloidal electrical field is close to the axial electrical field. The velocities of the propagation in poloidal and axial direction are estimated respectively, and the hybrid propagation modes involving the interchangeable helical pattern and the straight-line pattern propagating plasmas are explained from the viewpoint of multi-wave interaction.
This paper describes the design of a new type of pantograph-catenary arc simulation test device and simulation of the arc generated by the pantograph during operation under laboratory conditions. The influence of the burning position of the pantograph-catenary arc on the overvoltage of the traction system is studied. Corresponding suppression measures for the arcs are proposed, and the dynamics of the arc processes are carried out by theoretical simulation. The characteristics of the pantograph-catenary arc and the discharge process are analyzed, and the relationship between the characteristics of the pantograph and the arc is explored.
The streamer that driven by the specific pulse DC discharge parameters can stably form a threedimensional helical plasma channel in a long dielectric tube of the low-temperature plasma experiment, when there was neither external background magnetic field nor other factors that destroyed the poloidal symmetry of the tube. The formation mechanism and chirality of helical streamers are discussed here according to the surface electromagnetic standing wave theory. The shape of the helical streamers and the characteristics of helical branches are quantitatively analyzed to further expand the application of plasma and streamer theory in helix problem and chiral catalytic synthesis.
Helixes and chiralities are ubiquitous in nature and closely related to the origin of life, but the spontaneous assembly of such patterns has rarely been realized in low-temperature plasma jets which have numerous applications in biomedical engineering and materials processing. Recently chiral plasma plumes have been generated in the absence of any asymmetric factor. Under the condition of specific pulse DC discharge parameters, the discharge channels that originally propagated along a straight line turn into three dimensional helical plasma discharge channels spontaneously. And the pitch of the helixes can be guided by the external coils outside dielectric tubes in experiments. In this paper, we apply the finite element analysis method to simulate the electrostatic field of the chiral plasma guided by external coils. The effects of initial electric field and surface charges for the formation of the chiral plasma plumes are discussed respectively. These results have important implications for the production of chiral pharmaceuticals and nano-materials.INDEX TERMS Dielectric breakdown, electrostatic analysis, plasma sources, chiralities.
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