Properties of a warm plasma collisional sheath in an oblique magnetic field

Ou, Jing; Yang, Jinhong

doi:10.1063/1.4766476

Cited by 33 publications

(52 citation statements)

References 22 publications

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“…The red line shows the solution of the system (27)-(31) for e ¼ 0.005, and the blue line displays the solution of the system (27)-(31) for e ¼ 0.002. Some authors [19][20][21][22][23][24]37 have studied the effects of finite ion temperature to the sheath in an oblique magnetic field using similar fluid model like ours. In majority of above mentioned papers, the problem is treated on the sheath scale of the asymptotic two-scale limit.…”

Section: -7mentioning

confidence: 96%

“…Such ion source term has also been used by many authors who studied sheath in a magnetized plasma 3,8,9,18,22,23,32,33,35,37,42,44 The last ion source term considered in this work is written in the following form:…”

Section: Modelmentioning

confidence: 98%

“…In the sheath scale of the asymptotic two scale limit, the electric field at the sheath edge is zero, the ion flow at the sheath edge must fulfill the Bohm criterion, and at the sheath edge, the plasma is assumed to be neutral. 50 The approach taken by the authors in the above mentioned papers [19][20][21][22][23][24] and also some others 45,46 can therefore be summarized as follows. From the basic equations of the type (1)-(4) and an equation of state (e.g., (9)), a system of equations very similar to our system (27)-(31) is derived.…”

Section: -7mentioning

confidence: 99%

“…Since there cannot be a physical mechanism, where only positive ions and not also electrons would be created and annihilated, the model, which uses the Boltzmann relation for the electrons and S i 6 ¼ 0 for the ions, is not selfconsistent. Nevertheless, such model has been used extensively 3,8,9,18,22,23,32,33,35,42,44 for the analysis of magnetized plasma-wall transition by many authors. A possible reason for this could be the above mentioned problems related to the use of the zero source term (12) and the fact that the authors were probably not aware of the inconsistency that is introduced into the model in this way.…”

Section: -7mentioning

confidence: 99%

“…[19][20][21][22][23][24] Some authors analyzed the effects of the presence of two [25][26][27][28][29] or even multiple 30 species of positive ions. The sheath in a magnetized plasma in the presence of negative ions has been studied, [31][32][33][34][35] and even a combination of the presence of two positive and one negative ion species has been taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Fluid model of the sheath in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field: Some comments on ion source terms and ion temperature effects

Gyergyek

Kovačič

2015

Physics of Plasmas

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A one-dimensional fluid model of the magnetized plasma-wall transition region in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field is presented. The Boltzmann relation is assumed for the electrons, while the positive ions obey the ion continuity and momentum exchange equation. The ions are assumed to be isothermal. By comparison with a twofluid model, it is shown that assuming the Boltzmann relation for the electrons implies that there is no creation or annihilation of the electrons. Consequently, there should not be any creation and annihilation of the positive ions either. The models that assume the Boltzmann relation for the electrons and a non-zero ion source term at the same time are therefore inconsistent, but such models have nevertheless been used extensively by many authors. So, in this work, an extensive comparison of the results obtained using the zero source term on one hand and three different non-zero source terms on the other hand is made. Four different ion source terms are considered in total: the zero source term and three different non-zero ion source terms. When the zero source term is used, the model becomes very sensitive to the boundary conditions, and in some cases, the solutions exhibit large amplitude oscillations. If any of the three non-zero ion source terms is used, those problems are eliminated, but also the consistency of the model is broken. The model equations are solved numerically in the entire magnetized plasma-wall transition region. For zero ion temperature, the model can be solved even if a very small ion velocity is selected as a boundary condition. For finite ion temperature, the system of equations becomes stiff, unless the ion velocity at the boundary is increased slightly above the ion thermal velocity. A simple method how to find a solution with a very small ion velocity at the boundary also for finite ion temperature in the entire magnetized plasma-wall transition region is proposed. V C 2015 AIP Publishing LLC.

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Section: -7mentioning

confidence: 96%

Section: Modelmentioning

confidence: 98%

Section: -7mentioning

confidence: 99%

Section: -7mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Fluid model of the sheath in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field: Some comments on ion source terms and ion temperature effects

Gyergyek

Kovačič

2015

Physics of Plasmas

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Heat flow through a plasma sheath in the presence of secondary electron emission from plasma‐wall interaction

Zhao

2017

Contributions to Plasma Physics

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KEYWORDSenergy transmission coefficient, plasma sheath, secondary emission electron, sputtering yield INTRODUCTIONThe characteristics of a plasma sheath located between a plasma and a material surface play an important role in the plasma heat flow to the material surface during plasma-wall interaction. Several key factors influence the sheath structure, including electron emission, [1][2][3][4][5][6][7][8][9][10][11] magnetic field, [11][12][13][14][15] ion temperature, [13][14][15] and collision. [15][16][17] The most important one is the electron emission from plasma-wall interaction. It greatly reduces the sheath potential so that the thermal insulation may become substantially low because the potential drop across the sheath is a potential barrier for the incoming plasma electrons. The emission electron flux through the sheath may be regulated by the space-charge-limited (SCL) effect. The investigation of the plasma sheath in the presence of secondary electron emission (SEE) has been carried out based on several models. [1][2][3][4][5][6] However, many models consider cold ions, whereas the effect of ion temperature has not been studied systematically. For the edge plasma in fusion devices, the ion temperature is comparable to or higher than the electron temperature. [18][19][20][21] In addition, it is shown from sheath model results that the ion temperature influences the sheath properties. [13][14][15] Since the ion temperature in the tokamak edge region is important for the estimation of heat flux flowing to material surface and modelling plasma-wall interaction processes including impurity sputtering, [19] here we describe a plasma sheath with thermal ions in the presence of SEE. When heat flows through the plasma sheath, the sheath energy transmission coefficient , defined as the energy flux normalized by the particle exhaust flux times the electron temperature at the sheath entrance, [22] is used to estimate the energy flux flowing to the target plate in fusion device experiments and to provide boundary conditions in fusion plasma edge fluid codes.increases when SEE is taken into account or as the ion temperature is increased for a given SEE coefficient. [23] Another important physical process affected by the sheath structure is impurity production. Intrinsic impurities (e.g., Be, C, Mo, and W) are produced through erosion during the energy load on the plasma-facing material. The impurity sputtering yield depends

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