Sheath structure in a magnetized plasma
- Department of Physics, University of California, Los Angeles, Los Angeles, California 90024-1547 (United States)
The sheath formed between a magnetized plasma and a particle absorbing wall is examined for the case in which the magnetic field intercepts the wall at a small angle 0[degree][lt][epsilon][approx lt]9[degree], where sin [epsilon]=[bold B][center dot][ital [cflx n]]/[vert bar][ital B][vert bar], and [ital [cflx n]] is the unit normal to the wall. The model is time-independent and one-dimensional (1-D) with all functions varying only in the direction normal to the wall. The ions are modeled by a Maxwellian velocity distribution which is modified by the condition that ions, which would have hit the wall, are absent. For the electrons a fluid description is used, including the effects of electron--neutral collisions. The transport of particles due to turbulent electrostatic fluctuations is modeled by a constant electric field perpendicular to both [bold B] and [ital [cflx n]]. It is found that in the range of angles under consideration, there are two distinct regimes of sheath formation. If [epsilon][approx lt][bar [nu]]=[nu]/[Omega][sub [ital e]] (grazing incidence), where [nu] is the electron--neutral collision frequency and [Omega][sub [ital e]] is the electron cyclotron frequency, then the properties of the sheath are determined by a parameter [lambda] which is the ratio of the convective ([bold E][times][bold B]) and diffusive electron flows. If [lambda][approx lt]1, the wall potential is negative and the sheath scale length is on the order of an ion gyroradius. If [lambda][approx gt]1, the wall potential is positive and, for large [lambda], the sheath is characterized by two scales: a short length, which is a decreasing function of [lambda], adjacent to the wall, and the ion gyroradius farther from the wall. For [epsilon][much gt][bar [nu]], (oblique incidence) the potential at the wall is negative with a magnitude close to that of the unmagnetized plasma and is only weakly dependent on [epsilon].
- OSTI ID:
- 6493853
- Journal Information:
- Physics of Fluids B; (United States), Vol. 5:6; ISSN 0899-8221
- Country of Publication:
- United States
- Language:
- English
Similar Records
Lower-hybrid turbulence in a nonuniform magnetoplasma
Electron-phonon interaction in two dimensions: Variation of Im[Sigma]([epsilon][sub [ital p]],[omega]) with increasing [omega][sub [ital D]]/[ital E][sub [ital F]]