Electric field development inγ-mode radiofrequency atmospheric pressure glow discharge in helium

Abstract

Time development of electric field strength during radio-frequency sheath formation was measured using Stark polarization spectroscopy in a helium γ-mode radio-frequency (RF, 13.56 MHz) atmospheric pressure glow discharge at high current density (3 A cm −2 ). A method of time-correlated single photon counting was applied to record the temporal development of spectral profile of He I 492.2 nm line with a sub-nanosecond temporal resolution. By fitting the measured profile of the line with a combination of pseudo-Voigt profiles for forbidden (2 1 P-4 1 F) and allowed (2 1 P-4 1 D) helium lines, instantaneous electric fields up to 32 kV cm −1 were measured in the RF sheath. The measured electric field is in agreement with the spatially averaged value of 40 kV cm −1 estimated from homogeneous charge density RF sheath model. The observed rectangular waveform of the electric field time development is attributed to increased sheath conductivity by the strong electron avalanches occurring in the γ-mode sheath at high current densities.

Electric field measurement in the dielectric tube of helium atmospheric pressure plasma jet

“…More details about electric field measurement using this method in low pressure glow discharge, DBD, plasma jet, and radiofrequency atmospheric pressure discharge in helium can be found in our previous publications. [17][18][19][32][33][34][35][36][37][38][39] The method is based on the measurements of the distance between two helium lines, forbidden and allowed, which are shifting depending on the value of the external electric field. In order to separate two polarized components of the emitted light, plastic polarizer was mounted in front of the slit, and only p-polarized light was recorded.…”

State-by-state emission spectra fitting for non-equilibrium plasmas: OH spectra of surface barrier discharge at argon/water interface

“…Optical emission spectroscopy is a powerful non-invasive tool to investigate nonequilibrium plasmas [1,2,3,4,5]. Nowadays, crucial parameters such as electric field [6,7,8], electron density [9,10,11] or densities of important species [12] can be determined by methods of optical emission spectroscopy with high resolution and practically for any plasma of interest. In the case of the molecular spectra, also the rotational temperature as a measure for gas temperature can be obtained.…”

2D-resolved electric field development in helium coplanar DBD: spectrally filtered ICCD camera approach

“…On the other hand, the intensity ratio measured in the spot is consistent with the values measured at later times (see figure 8). Besides, fields higher than 30-60kV/cm can still occur in helium atmospheric pressure discharges, as in constricted radiofrequency discharge with metallic electrodes [11].…”

“…Using the Stark effect, the electric field is typically evaluated from a splitting or shifting of spectral lines of hydrogen or helium [4][5][6]. The so-called Stark polarization OES, developed originally for electric field measurement in low-pressure helium discharge [7], has also been used for the electric field measurement at atmospheric pressure in helium volume DBD [8], in an ionizing wave/streamer in 13 or 30kHz helium atmospheric pressure plasma jets [9,10] or in a γ-mode sheath of atmospheric pressure radio-frequency discharge [11]. The method has supplied valuable experimental data for the direct comparison of the electric field in helium atmospheric pressure discharges to the outputs of numerical studies, see e.g.…”