The spatiotemporal oscillation characteristics of the dielectric wall sheath in stationary plasma thrusters

Zhang, Fengkui; Yu, Daren; Ding, Yongjie; Li, Hong

doi:10.1063/1.3564898

Cited by 14 publications

(22 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[5][6][7][8] Therefore, understanding the characteristics of sheath near emissive surfaces is crucial for many plasma related applications and phenomena, e.g. emissive probe, 9,10 plasma thruster, 11,12 fusion reactor, 13,14 charging of spacecraft, 15,16 and dust levitation near lunar surface. [17][18][19] The effect of emission intensity usually defined as total electron emission coefficient (EEC) Γ, i.e.…”

Section: Introductionmentioning

confidence: 99%

Effect of total emitted electron velocity distribution function on the plasma sheath near a floating wall

Qing

Zhou

2017

AIP Advances

View full text Add to dashboard Cite

Electrons emitted from a solid surface can noticeably affect characteristics of plasma sheath surrounding that surface by modifying current balance at wall, charge separation in sheath region and Bohm criterion at sheath edge. We establish a static sheath model with kinetic electrons and cold ions to emphasize the effect of different total emitted electron velocity distribution functions (EEVDFs) on classic sheath solution and its structure transition. Four total EEVDFs with same average energy are considered separately. It is found that total EEVDFs influence the sheath solution and the threshold of total electron emission coefficient (EEC) for classic sheath dramatically, and can cause no solution for critical space-charge limited (SCL) sheath. These results indicate that, as EEC increases from zero gradually, the sheath will not transit from classic sheath to SCL sheath structure for some special total EEVDFs.

show abstract

Section: Introductionmentioning

confidence: 99%

Effect of total emitted electron velocity distribution function on the plasma sheath near a floating wall

Qing

Zhou

2017

AIP Advances

View full text Add to dashboard Cite

show abstract

“…In plasma devices, observed changes resulting from SEE-driven instabilities may be overlooked and assumed to be driven by processes in the plasma interior. In light of the nonsteady sheath effects observed in this paper and elsewhere in the literature 7,8,9,10,11,12,13,14,15,16,17 , a static sheath cannot be taken for granted in practice when SEE is very strong.…”

Section: Discussionmentioning

confidence: 92%

“…Nonsteady surface effects due to SEE have been observed in numerous plasma simulations 7,8,9,10,11,12,13,14 and experiments 15,16,17 . Because the plasma properties in any device are coupled to the PSI, this can affect more than just the surface.…”

Section: Secondary Electron Emission (See) Is Important In a Wide Varmentioning

confidence: 99%

See 1 more Smart Citation

Instability, collapse, and oscillation of sheaths caused by secondary electron emission

2012

View full text Add to dashboard Cite

The Debye sheath is shown to be unstable under general conditions. For surface materials with sufficient secondary electron emission (SEE) yields, the surface's current-voltage characteristic has an unstable branch when the bulk plasma temperature (T e ) exceeds a critical value, or when there are fast electron populations present. The plasma-surface interaction becomes dynamic where the sheath may undergo spontaneous transitions or oscillations. Using particle-in-cell simulations, we analyze sheath instabilities occurring in a high T e plasma slab bounded by walls with SEE. As the plasma evolves, whenever the sheath enters an unstable state, its amplitude rapidly collapses, allowing a large flux of previously trapped electrons to hit the wall. These hot electrons induce more than one secondary on average, causing a net loss of electrons from the wall. The sheath collapse quenches when the surface charge becomes positive because the attractive field inhibits further electrons from escaping. Sheath instabilities influence the current balance, energy loss, cross-B-field transport and even the bulk plasma properties. Implications for discharges including Hall thrusters are discussed. More generally, the results show that common theories that treat emission as a fixed (time-independent) "coefficient" do not capture the full extent of SEE effects. a) Author to whom correspondence should be addressed. Electronic

show abstract

“…21 With a further study, I find that there are temporal and spatial oscillations in the sheath. 22 For a temporal-oscillating sheath, only the collisions between electrons and wall produce a conduction current. For a spatial oscillating sheath, mainly electrons that are reflected by the sheath produce a non-collisional near-wall conduction current.…”

Section: Introductionmentioning

confidence: 99%

Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster

Zhang

Kong

et al. 2014

Physics of Plasmas

Self Cite

View full text Add to dashboard Cite

Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the nearwall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO 2 . Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current. The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations. V C 2014 AIP Publishing LLC. INTRODUCTIONAt present, using Hall-effect thrusters in interplanetary missions and geostationary satellites with affordable propellants can reduce costs and improve economics. Optional propellants include gases of argon, krypton, nitrogen, and nitrogen dioxide. Although the atomic masses of these gases are smaller and the degrees of first ionization are higher than xenon, thereby yielding lower propulsive efficiency, these propellants are more affordable. 1 The Hall-effect thruster is universally applicable in many countries involved in aeronautics and in which giving the krypton-plasma thruster greater research attention. [2][3][4] Although previous studies show that compared with xenon, the thruster efficiency is low with krypton, some studies show that improvements in efficiency can be made in propellant utilization rate, along with other means, which approach the efficiency of xenon. [5][6][7][8]12 Other research shows that thruster performance based on krypton is significantly lower than that on xenon. 6,[9][10][11] With a low utilization rate of krypton, krypton (with a decrease of 37% in atomic mass) relative to xenon under normal conditions, the thrust decreases 20%-30% and the specific impulse decreases 37%. 13 Previous studies have concluded that the main factor of krypton's low efficiency is its low propellant utilization rate. To study the reason for this low efficiency, it is necessary to study the plasma in the thruster's discharge channel. 14 Estimates of classical conduction produced by collisions between electrons and atoms is far less than experimental results; that is, other unusual conduction occurs allowing electrons to cross magnetic field lines. 15 Some researchers believe that this unusual conduction is due to collective oscillation in the plasma of the thruster, which is called Bohm conduction. Bohm conduction is used to explain the reason why the current is greater than that produced solely by collision between electrons and atoms in discharge devices using plasma with a high degree of ionization. The Bohm conduct...

show abstract

The spatiotemporal oscillation characteristics of the dielectric wall sheath in stationary plasma thrusters

Cited by 14 publications

References 17 publications

Effect of total emitted electron velocity distribution function on the plasma sheath near a floating wall

Effect of total emitted electron velocity distribution function on the plasma sheath near a floating wall

Instability, collapse, and oscillation of sheaths caused by secondary electron emission

Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster

Contact Info

Product

Resources

About