glow discharges
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Author(s):  
Vladimir Kolobov ◽  
Juan Alonso Guzmán ◽  
R R Arslanbekov

Abstract A self-consistent hybrid model of standing and moving striations was developed for low-current DC discharges in noble gases. We introduced the concept of surface diffusion in phase space (r,u) (where u denotes the electron kinetic energy) described by a tensor diffusion in the nonlocal Fokker-Planck kinetic equation for electrons in the collisional plasma. Electrons diffuse along surfaces of constant total energy ε=u-eφ(r) between energy jumps in inelastic collisions with atoms. Numerical solutions of the 1d1u kinetic equation for electrons were obtained by two methods and coupled to ion transport and Poisson solver. We studied the dynamics of striation formation in Townsend and glow discharges in Argon gas at low discharge currents using a two-level excitation-ionization model and a “full-chemistry” model, which includes stepwise and Penning ionization. Standing striations appeared in Townsend and glow discharges at low currents, and moving striations were obtained for the discharge currents exceeding a critical value. These waves originate at the anode and propagate towards the cathode. We have seen two types of moving striations with the 2-level and full-chemistry models, which resemble the s and p striations previously observed in the experiments. Simulations indicate that processes in the anode region could control moving striations in the positive column plasma. The developed model helps clarify the nature of standing and moving striations in DC discharges of noble gases at low discharge currents and low gas pressures.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jing Li ◽  
Bingying Lei ◽  
Jing Wang ◽  
Boping Xu ◽  
Shuang Ran ◽  
...  

AbstractAtmospheric gas discharge is very likely to constrict into filaments and diffuse plasma formation is inefficient in most cases. Developing cost-efficient atmospheric diffuse plasma devices represents a significant challenge for high performance in biomedical decontamination and material processing. Here, we propose an alternative roadmap to produce a diffuse argon plasma jet by expanding and quenching the existing filamentary discharge at the initial or middle stage of streamer development. Possible mechanisms are summarized. With the gas flow velocity comparable to the ion drift one, enhancing ambipolar diffusion near the edge of the positive-streamer channel promotes the radial diffusion of newly-produced electrons, realizing the radial expansion of channel. Weakening electric field in front of the streamer head through head expansion and field offset, prevents the further development of streamer, leading to a positive-pseudo-streamer discharge. Reducing electric field in front of the negative-streamer head through ion compensation, impedes the initial growth of streamer, resulting in a negative pulseless glow discharge. The positive-pseudo-streamer and negative pulseless glow discharges function together to form the diffuse plasma jet.


2021 ◽  
pp. 50-56
Author(s):  
G.P. Glazunov ◽  
V.E. Moiseenko ◽  
S.M. Maznichenko ◽  
M.N. Bondarenko ◽  
A.L. Konotopskiy ◽  
...  

The experiments were carried out to determine the vacuum-plasma characteristics (mainly erosion and outgassing rate in a vacuum) of the stainless steel 12X18H10T before and after processing the walls of the vacuum chamber with the glow discharge and combined, glow-microwave plasma discharges in argon atmosphere. The current-voltage characteristics, the electron density and electron temperature were measured. It was observed that the discharge voltage in the combined regime is significantly lower than in glow discharges. In some modes, this voltage decrease can be up to 200 V. It was shown that erosion of stainless steel 12X18H10T in the combined discharges is 70 %, less than in the glow discharges. Measurements were made of the outgassing rate of 12X18H10T stainless steel with the thermal desorption probe in situ in the DSM-1 vacuum chamber. It was shown that cleaning the chamber wall by the glow discharge during 5 h leads to a decrease in the outgassing rate from 5.5·10-5 to 1·10-5 (Torr.l)/(s.cm2) . When the chamber wall is treated with GM discharge starting from nearly the same initial conditions the outgassing rate decreased to 3·10-6 (Torr.l)/(s.cm2). Spectral measurements of the plasma radiation of a glow and combined discharges show a decrease in the ratio of the peaks of argon ions and neutrals during the transition from a glow discharge to a combined one.


Author(s):  
R.V. Yakushin ◽  
A.V. Chistolinov ◽  
V.S. Boldyrev ◽  
E.N. Ofitserov ◽  
I.N. Solovieva ◽  
...  

Plasma chemistry is part of the development of high technology that meets the modern requirements of greening and resource conservation. The study of physic-chemical laws and processes occurring in the zone of action of electric discharge plasma near the surface of a liquid is of high scientific and applied interest. In the study, developed and patented by a team of authors, plasma-chemical reactors were used, which implement the treatment of a liquid with both barrier and glow discharges near the surface of the liquid phase in a flow-through mode. Solutions of primary and secondary aliphatic alcohols were used as a model object of plasma-chemical treatment. As a result of the study, the mechanisms of liquid-phase oxidation of primary and secondary aliphatic alcohols during plasma-chemical treatment of water were proposed. The emission spectra of electric discharges at the gas-liquid interface in the presence of dissolved organic substances were obtained and analyzed. Spectral studies of electrodischarge plasma in the liquid-liquid zone confirmed the differing composition of the inorganic oxidation products of primary and secondary aliphatic alcohols. When deciphering the spectra of barrier and glow discharges, the characteristic emission bands of nitrogen N2, OH-radicals and nitric oxide, as well as lines of atomic hydrogen H and oxygen O were shown. In addition, the effect of the nature of the organic substances contained in the treated water on the characteristics of the electric discharge plasma was shown


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