Vacuum surface flashover and high pressure gas streamers

Abstract

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Plasma-surface interaction: dielectric and metallic targets and their influence on the electric field profile in a kHz AC-driven He plasma jet

“…The elongation of the plasma plume when a target is present, even if it is a glass target with low-permittivity, might be caused by different gas mixing like discussed above, but it is probable that this is also an electrical effect of the target. The presence of a dielectric material, even with low-permittivity, has been shown to modify the dynamics with which the fast ionization waves travel [49][50][51][52][53][54][55]. The dielectric does not even have to be in the path of the ionization wave to modify its trajectory, it only has to be in its close vicinity [56].…”

Speed of streamers in argon over a flat surface of a dielectric

“…The question is, why is propagation over the dielectric surface faster than through the gas? Many scientists assumed that this is the result of the dielectric properties of the material [2][3][4][5][6][7][8][9][10]. Akyuz et al [7] suggested a combination of permittivity of the dielectric and accumulated negative charge on its surface was responsible for increase in the ionization rate on the dielectric surface, that speeds up the discharge.…”

“…On the other hand, photoemission of electrons from the cathode or the dielectric surface can be viewed as a mechanism partly responsible for the fast propagation. Although it still has not been proven, photoemission of electrons from the dielectric surface is a concept proposed quite a few times already [2][3][4][5][6]. The area around the streamer tip is very active with different reactions such as ionization, excitations and deexcitations of argon atoms.…”

“…Photoemission of electrons from the insulator surface was also proposed by many other researchers [3][4][5][6], but Akyuz et al [7] tried to solve the puzzle of high streamer velocities along the insulating surface by assuming they were due to a combination of the effect of permittivity of the dielectric and accumulated negative charge on the surface, which gives rise to an increase in the ionization rate. In order to unravel the influence of an insulating surface on the basic properties of streamers, extensive measurements were done, determining streamer velocities that depend on various factors [4,5,7,8].…”

“…Most of the gathered knowledge comes from electrical engineers, who have been troubled by this phenomenon for years [2][3][4][5][6][7][8][9][10] because material interaction with the streamer development is of significance when it comes to insulation performance. For the most part, their research was done in air and in atmospheric pressure.…”