Electron kinetics in standing and moving striations in argon gas

Levko, Dmitry

doi:10.1063/5.0029847

Cited by 10 publications

(9 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The growth rate, wave number and angular frequency or phase velocity of the instability can be deduced from the results of the PIC-MCC simulation, and their variations with the reduced electric field 𝐸 0 𝑝 ⁄ can be compared with those given by the linear analysis of the fluid model, eqs. ( 21) and (22). These comparisons are shown in Figure 14 and Figure 15 for the wavelength and growth rate respectively.…”

Section: G Comparison With the Pic-mcc Modelmentioning

confidence: 93%

“…[4][5][6] ). Recently, a self-consistent hybrid simulation of dc and rf positive column plasmas in argon was presented 22 under conditions where the effect of Coulomb collisions and stepwise ionization were negligible. The electric field was not imposed but rather obtained from Poisson's equation, electron transport was described kineticaly with a Monte Carlo simulation, and continuity and drift-diffusion equations were used for positive ions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Boeuf

2022

Physics of Plasmas

View full text Add to dashboard Cite

A one-dimensional Particle-In-Cell Monte Carlo Collisions (PIC-MCC) method has been used to model the development and propagation of ionization waves in neon and argon positive columns. Low current conditions are considered, i.e. conditions where stepwise ionization or Coulomb collisions are negligible (linear ionization rate). This self-consistent model describes the development of self-excited moving striations, reproduces many of the well-known experimental characteristics (wavelength, spatial resonances, potential drop over one striation, electron "bunching" effect) of the ionization waves called p, r and s waves in the literature and sheds light on their physical properties and on the mechanisms responsible for their existence. These are the first fully kinetic self-consistent simulations over a large range of conditions reproducing the development of p, r and s ionization waves. Although the spatial resonances and the detailed properties of the striations in the non-linear regime are of kinetic nature, the conditions of existence of the instability can be obtained and understood from a linear stability analysis of a three-moment set of quasi-neutral fluid equations where the electron transport coefficients are expressed as a function of electron temperature and are obtained from solutions of a 0D Boltzman equation. An essential aspect of the instability leading to the development of these striations is the non-Mawellian nature of the electron energy distribution function in the uniform electric field prior to the instability onset, resulting in an electron diffusion coefficient in space much larger than the energy diffusion coefficient.

show abstract

Section: G Comparison With the Pic-mcc Modelmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Boeuf

2022

Physics of Plasmas

View full text Add to dashboard Cite

show abstract

“…Omitting only the N 2 (A 3 Σ) excitation, N-elastic and N-ionization reactions from the reaction scheme did not have any noticeable effect on the striations (not shown here). Previous studies [23,27] have demonstrated that excluding the loss term due to ambipolar diffusion to the wall fails to produce the positive column. In our case, both the ambipolar diffusion to the wall and the vibrational excitation reactions play key roles in forming the standing striation in molecular nitrogen gas.…”

Section: (B)) the Density Of Nmentioning

confidence: 95%

“…, where Λ = R tube 2.4 is the transverse discharge length (R tube is the tube or discharge radius) [27,31] and…”

Section: Mathematical Model and Problem Geometrymentioning

confidence: 99%

“…Numerical studies of the non-local electron kinetics leading to plasma stratification have been reported in the literature [24][25][26]. In a recent study, Levko [27] observed standing and moving striations in low-pressure dc and rf argon discharges using one-dimensional PIC simulations; however, no mechanism of stratification has been identified. Despite many theoretical and modeling studies of plasma stratification in several gases, modeling striations in diatomic gases has been limited.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Striations in moderate pressure dc driven nitrogen glow discharge

Tahiyat¹,

Stephens²,

Kolobov³

et al. 2021

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Plasma stratification has been studied for more than a century. Despite the many experimental studies reported on this topic, theoretical analyses and numerical modeling of this phenomenon have been mostly limited to rare gases. In this work, a one-dimensional fluid model with detailed kinetics of electrons and vibrationally excited molecules is employed to simulate moderate-pressure (i.e. a few Torrs) dc discharge in nitrogen in a 15.5 cm long tube of radius 0.55 cm. The model also considers ambipolar diffusion to account for the radial loss of ions and electrons to the wall. The proposed model predicts self-excited standing striations in nitrogen for a range of discharge currents. The impact of electron transport parameters and reaction rates obtained from a solution of local two-term and a multi-term Boltzmann equation on the predictions are assessed. In-depth kinetic analysis indicates that the striations result from the undulations in electron temperature caused due to the interaction between ionization and vibrational reactions. Furthermore, the vibrationally excited molecules associated with the lower energy levels are found to influence nitrogen plasma stratification and the striation pattern strongly. A balance between ionization processes and electron energy transport allows the formation of the observed standing striations. Simulations were conducted for a range of discharge current densities from ∼0.018 to 0.080 mA cm−2, for an operating pressure of 0.7 Torr. Parametric studies show that the striation length decreases with increasing discharge current. The predictions from the model are compared against experimental measurements and are found to agree favorably.

show abstract

Influence of the Dufour effect on striations formation in radio-frequency discharges

Levko,

Raja

2024

Physics of Plasmas

View full text Add to dashboard Cite

In recent years, interest in striation phenomena in radio frequency (rf) discharges has risen due to the availability of new experimental data and the implementation of new computational models. Depending on the conditions, different mechanisms of discharge striations are realized. These are the ionization instability, the instability due to the electron attachment to electronegative gases, or the instability due to thermoelectric transport. Although the first two mechanisms were modeled quite extensively in recent years, the understanding of the influence of the Dufour effect originating from plasma density gradients on the stability of radio frequency discharges in long tubes remains poor. In this paper, the influence of this mechanism on the longitudinal striations of radio frequency discharge is presented using a one-dimensional model of argon discharge driven with rf excitation under intermediate pressure conditions of 0.5 Torr. It is found that striation formation is sensitive to the value of the thermoelectric heat transport coefficient in the low electron temperature range. The critical value of this coefficient necessary for the instability onset is derived using the linear stability analysis.

show abstract

Electron kinetics in standing and moving striations in argon gas

Cited by 10 publications

References 25 publications

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Striations in moderate pressure dc driven nitrogen glow discharge

Influence of the Dufour effect on striations formation in radio-frequency discharges

Contact Info

Product

Resources

About