The magnetic presheath in the plasma-wall transition
- Tel Aviv Univ. (Israel)
The steady state plasma parameters distribution in real plasma devices are determined by the plasma boundary transition. If the plasma is bounded by a wall, the stationary transitional sheath exists only if ion velocity V satisfies the Bohm condition at the sheath boundary: V>C{sub s}=((kT{sub e}+{gamma}{sub i}kT{sub i})/M){sup 0.5} where k is Boltzmann constant, T{sub e} is the electron temperature, {gamma}{sub i} is the adiabatic constant, T{sub i} is the ion temperature, M is the ion mass. The ions are accelerated up to an energy equal to the energy of the electrons in some quasineutral presheath. The presheath may be dominated by collisions, ionization, and geometric current concentration effects. The magnetic field may exert an additional influence on the presheath Chodura studied collisionless sheath in a magnetic field which intersects a wall at an arbitrary angle. Both kinetic and fluid models were used to describe plasma behavior in the presheath, assuming quasineutrality. The potential distribution and oscillations in the presheath were obtained. The presheath thickness scales with the ion gyroradius at the sound speed and with the angle between the magnetic field and wall surface. The collisional presheath in the magnetic field was analyzed by Riemann. A fluid model with assumptions close to Chodura and a collision term with constant collision frequency was used. The potential distribution in the presheath for different magnetic fields, collision frequencies and angles of the magnetic field was determined.
- OSTI ID:
- 212844
- Report Number(s):
- CONF-950749--
- Country of Publication:
- United States
- Language:
- English
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