A self-consistent two-fluid model of a magnetized plasma-wall transition

Journal Article · Tue Sep 15 04:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4931169· OSTI ID:22493784

Gyergyek, T. ^[1]; Kovačič, J. ^[2]

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1. University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana (Slovenia)
2. Jožef Stefan Institute, Jamova 39, P.O. Box 100, 1000 Ljubljana (Slovenia)

A self-consistent one-dimensional two-fluid model of the magnetized plasma-wall transition is presented. The model includes magnetic field, elastic collisions between ions and electrons, and creation/annihilation of charged particles. Two systems of differential equations are derived. The first system describes the whole magnetized plasma-wall transition region, which consists of the pre-sheath, the magnetized pre-sheath (Chodura layer), and the sheath, which is not neutral, but contains a positive space charge. The second system of equations describes only the neutral part of the plasma-wall transition region—this means only the pre-sheath and the Chodura layer, but not also the sheath. Both systems are solved numerically. The first system of equations has two singularities. The first occurs when ion velocity in the direction perpendicularly to the wall drops below the ion thermal velocity. The second occurs when the electron velocity in the direction perpendicularly to the wall exceeds the electron thermal velocity. The second system of differential equations only has one singularity, which has also been derived analytically. For finite electron to ion mass ratio, the integration of the second system always breaks down before the Bohm criterion is fulfilled. Some properties of the first system of equations are examined. It is shown that the increased collision frequency demagnetizes the plasma. On the other hand, if the magnetic field is so strong that the ion Larmor radius and the Debye length are comparable, the electron velocity in the direction perpendicularly to the wall reaches the electron thermal velocity before the ion velocity in the direction perpendicularly to the wall reaches the ion sound velocity. In this case, the integration of the model equations breaks down before the Bohm criterion is fulfilled and the sheath is formed.

• OSTI ID: 22493784
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 22; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANNIHILATION
BOHM CRITERION
DEBYE LENGTH
DIFFERENTIAL EQUATIONS
ELECTRON COLLISIONS
ELECTRONS
ION ACOUSTIC WAVES
ION COLLISIONS
IONS
LARMOR RADIUS
MAGNETIC FIELDS
ONE-DIMENSIONAL CALCULATIONS
PLASMA
SINGULARITY
SPACE CHARGE
VELOCITY
WALLS