Plasma confinement by surface magnetic fields

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7211615

Samec, T K

Plasma confinement in permanent magnet multi-dipole line cusp configurations is studied. Analytic closed form expressions for the confining magnetic fields are given which agree well with experimental field measurements. Particle escape rates are calculated for a number of possible electric and magnetic field profiles, using appropriate functional forms for the particle distribution functions. A detailed analysis of particle orbits, including a careful consideration of adiabatic invariance for particles which come from regions of low magnetic field, confirms the validity of the assumptions used in calculating particle escape rates. The structures found for low beta charge neutral sheaths show that only sheaths with widths larger than an ion cyclotron radius can be stable. A single particle model based on the proceeding work, which includes plasma production by primary ionizing electrons and plasma loss through sheaths with widths of order of an ion gyroradius is constructed. This theoretical model correctly predicts the experimentally observed behavior of d.c. discharged plasmas confined within multi-dipole magnetic fields. Since the open field lines associated with line cusp geometries and the associated loss of plasma particles may be eliminated by the use of high order multipole geometries, the question of controlling end losses in a linear cylindrical higher order multipole configuration has been examined. A slow tapering of the cylindrical radius leads to the existence of a new adiabatic invariant and the associated confinement of particles outside a velocity space loss cone due to adiabatic mirroring. An expression for this invariant correct to second order in the taper angle is derived and the residual third order terms are used to construct a non-adiabatic pitch angle diffusion equation which yields a rather high upper bound for the confinement time.

• Research Organization: California Univ., Los Angeles (USA)
• OSTI ID: 7211615
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101* -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
ADIABATIC INVARIANCE
ANALYTICAL SOLUTION
CONFINEMENT
CUSPED GEOMETRIES
MAGNETIC FIELD CONFIGURATIONS
OPEN CONFIGURATIONS
PLASMA CONFINEMENT
PLASMA SHEATH