Temporally resolved optical emission spectroscopic investigations on a nanosecond self-pulsing micro-thin-cathode discharge

Abstract

At atmospheric pressure in Ar, a micro-thin-cathode discharge operates in a self-pulsing mode due to periodic ignition of a nanosecond spark discharge with a long living afterglow (several hundred nanoseconds). In this mode, optical emission spectra of the nanosecond spark and the afterglow are investigated. The electron density and temperature in the pure Ar discharge are measured by the Stark broadening and shift of the Ar 3p 6 → 1s 5 transition (415.859 nm). The nanosecond spark has an electron density of the order of 10 17 cm −3 and an electron temperature of 5 eV. The gas temperature is obtained by analyzing the emission spectra of the N 2 second positive system with an admixture of 0.5% N 2 . The measured gas temperature agrees very well with the result of a zero-dimensional kinetic simulation. The temporal development of the spatial distribution of separate emission lines shows that not only the nanosecond spark but the afterglow is also strongly localized. The temporal development of the emission spectrum provides powerful proof that the nanosecond spark discharge, due to thermionic emission, occurs in the self-pulsing mode with nanosecond current peaks.

Ignition and extinction phenomena in helium micro hollow cathode discharges

“…Then, the current is self-pulsed as reported by several other teams. [17][18][19] Figure 6 shows current and voltage waveforms in this particular regime with applied voltage fixed to 380 V. At point A, the voltage increases until it reaches the breakdown potential (point B). The current appears suddenly (at point B) and reaches a value of 28 mA at point C. The pulse duration is typically 1-2 ls, depending on the pressure and applied voltage.…”

Understanding the depletion of electrons in dusty plasmas at atmospheric pressure

“…particular relevance to this study, the resulting broadening of the emission line profile has been used to determine the average electron density in atmospheric-pressure plasmas [26,28,29].…”

Advanced Optical Diagnostics of Atmospheric Pressure Plasma

“…The effects of these broadenings need to be separated to obtain the Stark part and accurate deconvolution procedures normally are required for this purpose [33]. Other atomic lines are also possible for n e measurement based on their Stark broadening if hydrogen gas is absent, for example, He (447.1 nm) or Ar (415.9 nm) lines [34,35].…”