Electron kinetic effects in atmospheric dielectric-barrier glow discharges

Abstract

Large-volume atmospheric dielectric-barrier discharges (DBD) are particularly useful for processing applications when they operate in their homogeneous mode. A vast majority of their theoretical studies is currently based on the hydrodynamic treatment in which electrons are assumed to be in equilibrium with the local electric field. Recognizing that this assumption is incorrect in the sheath region, we report the development of an electron-hybrid model to treat electrons kinetically and all other particles hydrodynamically. Through numerical examples, it is shown that the mainstream hydrodynamic model underestimates gas ionization and discharge current. Using the hybrid model, it is demonstrated that variation in the amplitude of the applied voltage does not significantly alter sheath characteristics in terms of the electric field and the electron mean energy. Also gas ionization in atmospheric DBD is found to be significant only over a short timescale of 1 μs. Compared with dc atmospheric pressure glow discharges, atmospheric DBD are shown to have a smaller electron mean energy and a larger sheath thickness.

Sub-60 °C atmospheric helium–water plasma jets: modes, electron heating and downstream reaction chemistry

“…For atmospheric dry helium plasmas, the mean electron temperature is reported to be about 1 -5 eV [69] [70]. Therefore T 13 of 7,988 -8,265 K in Fig.…”

Physical Mechanisms of Inactivation of Bacillus subtilis Spores Using Cold Atmospheric Plasmas

“…However, for the atmospheric plasmas, they are unlikely to contribute significantly to the microbial inactivation. This is because the maximum electric field usually occurs at the cathode surface and then reduces exponentially to a fraction of its peak value over a very short distance of less than 300 µm [16], [18]. Clearly, it was difficult to position the membrane well within 300 µm from the cathode, and so, the electric field was unlikely to be a major factor in most plasma-inactivation experiments.…”

“…For cases of in situ inactivation where the microbial samples were immersed within the plasmageneration region, the electric field could be significant. The maximum electric field in the nonthermal atmospheric glow discharges in helium is known to range from a few kilovolts per centimeter in the radio-frequency APGD [12], [18], through 20-30 kV/cm in the atmospheric dielectric-barrier glow discharges [16], to over 50 kV/cm in the dc APGD [19]. Such high electric fields could potentially breach the cell membrane [20].…”

“…By using the numerical models for the dielectric-barrier discharges in the atmospheric helium [15], [16], the recombination of the free electrons with the helium ions was found numerically to reduce the electron density by one magnitude over a period of 2-20 ms. This was consistent with the relevant experimental data [17].…”

Electron density and temperature of gas-temperature-dependent cryoplasma jet

“…This is in good agreement with N e for a general helium DBD generated at atmospheric pressure, where N e ranges from 10 9 to on the order of 10 11 cm À3 . [27][28][29] Moreover, the electron temperature gradually increased as T pg was decreased to 60 K but rapidly decreased below 60 K. At gas temperatures above approximately 60 K, as T pg was decreased, the applied gap voltage was increased and the value of D e /l e increased monotonically as shown in Fig. 3.…”