Two-dimensional positive column structure in a discharge tube with radius discontinuity

Zobnin, A. V.; Usachev, A. D.; Петров, О. Ф.; Фортов, В. Е.

doi:10.1063/1.4901307

Cited by 18 publications

(8 citation statements)

References 54 publications

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“…The first one applies the theoretical model for the particle wake potential in collisional flowing plasmas [ 16 ], and another approach introduces the trapped ion distribution and associated dipole moment induced by external electric fields [ 18 ]. The results were then applied to the parameter space of the PK-4 facility on board ISS, using the probe measurements of the plasma parameters [ 7 , 8 , 9 , 10 ]. It was found that, in the experimental conditions, the local variations in the (free or trapped) ion charge distribution induced by weak discharge electric fields reduce significantly the repulsion between two particles, and it can be, furthermore, turned into explicit attraction at realistic interparticle distances.…”

Section: Discussionmentioning

confidence: 99%

“…Here, we have assumed that

, where the standard notations for the electron temperature

, ion mass

, and ion-neutral collision frequency

are used. Calculations in Figure 2 and everywhere in the paper are done using the respective probe measurements of the discharge parameters made in the PK-4 chamber in the absence of dust [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

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Possible Mechanisms of String Formation in Complex Plasmas at Elevated Pressures

Yaroshenko

Pustylnik

2021

Molecules

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Possible mechanisms of particle attraction providing formation of the field aligned microparticle strings in complex plasmas at elevated gas pressures are theoretically investigated in the light of the Plasmakristall-4 (PK-4) experiment on board the International Space Station. The particle interaction energy is addressed by two different approaches: (i) using the dynamically screened wake potential for small Mach numbers derived by Kompaneets et al., in 2016, and (ii) introducing effect of polarization of the trapped ion cloud by discharge electric fields. Is is found that both approaches yield the particle interaction energy which is independent of the operational discharge mode. In the parameter space of the performed experiments, the first approach can provide onset of the particle attraction and string formation only at gas pressures higher than 40–45 Pa, whilst the mechanism based on the trapped ion effect yields attraction in the experimentally important pressure range 20–40 Pa and may reconcile theory and observations.

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Section: Discussionmentioning

confidence: 99%

“…Here, we have assumed that

, where the standard notations for the electron temperature

, ion mass

, and ion-neutral collision frequency

Section: Introductionmentioning

confidence: 99%

Possible Mechanisms of String Formation in Complex Plasmas at Elevated Pressures

Yaroshenko

Pustylnik

2021

Molecules

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“…Thereby, we include the effect of particle charge decrease as compared to the charge of an isolated particle, which is sometimes called "the charge cannibalism" [52,53]. Using (24) we obtain for this point…”

Section: Analysis Of Experiemntal Datamentioning

confidence: 99%

Dust acoustic waves in three-dimensional complex plasmas with a similarity property

Zhukhovitskii

2015

Phys. Rev. E

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Dust acoustic waves in the bulk of a dust cloud in complex plasma of low-pressure gas discharge under microgravity conditions are considered. The complex plasma is assumed to conform to the ionization equation of state (IEOS) developed in our previous study. This equation implies the ionization similarity of plasmas. We find singular points of IEOS that determine the behavior of the sound velocity in different regions of the cloud. The fluid approach is utilized to deduce the wave equation that includes the neutral drag term. It is shown that the sound velocity is fully defined by the particle compressibility, which is calculated on the basis of the used IEOS. The sound velocities and damping rates calculated for different three-dimensional complex plasmas both in ac and dc discharges demonstrate a good correlation with experimental data that are within the limits of validity of the theory. The theory provides interpretation for the observed independence of the sound velocity on the coordinate and for a weak dependence on the particle diameter and gas pressure. Predictive estimates are made for the ongoing PK-4 experiment.

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“…Although double layers have been mostly studied for collisionless plasmas, they also appear in collisional plasma (both current-carrying and current-free); examples are the current carrying DL in the cathode region of DC (direct current) discharges with two field reversals in the negative glow and Faraday dark space [37] and in the anode region of DC discharges [38]; the positive column of DC discharges in a constricted tube shows the formation of a DL often associated with the appearance of standing striations near the tube constriction [39,40]. The DL is also found in hollow cathode collisional discharges in which the anode is placed in a separate vacuum vessel communicating with the discharge chamber through an orifice [41].…”

Section: Introductionmentioning

confidence: 99%

Current-Free Electric Double Layer in a Small Collisional Plasma Thruster Nozzle Simulation

Charles

Boswell

2019

Front. Phys.

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A computational fluid dynamics and plasma model of a collisional (∼ a few Torr) radiofrequency (at 13.56 MHz) argon plasma capacitively coupled in a converging-diverging nozzle (applied to the optimization of electrothermal plasma thrusters for space use) shows the formation of a strong stationary current-free double layer (CFDL) at the 1.5 mm diameter nozzle throat for a downstream pressure of ∼ 0.1 Torr. The cycle average magnitude of the double layer potential is DL = 77 V and the electron temperature at the high potential edge of the double layer is k B T e = 2.64 eV, yielding a strength of DL / (k B T e) ∼ 30. The double layer is 1.2 mm wide which corresponds to ∼ 90 Debye lengths. The axial electric field of the double layer accelerates ions along the nozzle to a maximum drift velocity of 17 km s −1 , about 3.3 times the ion sound speed, and their kinetic energy is transferred to neutrals by ion-neutral charge exchange collisions. The ion transit time τ i through the potential structure spontaneously forming at the nozzle throat is about 5 times the radiofrequency excitation period τ RF. These findings are discussed in the broader context of double layer physics and the dynamics of their formation as well as in the context of electrothermal thruster optimization in which neutral propellant heating via ion-neutral charge exchange collisions is the main source of thrust.

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Two-dimensional positive column structure in a discharge tube with radius discontinuity

Cited by 18 publications

References 54 publications

Possible Mechanisms of String Formation in Complex Plasmas at Elevated Pressures

Possible Mechanisms of String Formation in Complex Plasmas at Elevated Pressures

Dust acoustic waves in three-dimensional complex plasmas with a similarity property

Current-Free Electric Double Layer in a Small Collisional Plasma Thruster Nozzle Simulation

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