Determination of Spatial Distribution of Plasma Current Density by Multibeam FIR Interferometry/Polarimetry

A method is derived for inferring the point-wise current density given the shape of the outer plasma boundary ∫i neds and ∫i neB→d→s, where ne is the electron density, d→s is an increment of path length, and Bd→ is the magnetic field strength. The i is an index for the several integral traverses that are required. The integral quantities are assumed to be obtainable from far infrared (FIR) interferometer/polarimeter measurements [1], and the outer plasma boundary shape could be obtained from plasma loop probe measurements [2]. The method obtains a current density distribution that is consistent with ∇ . Bd→ = 0, ∇ × BneB→ = μ d→sj, assuming that the ne contour lines follow the B-field lines [3], [4], as well as the measured line integrals, and the measured outer plasma boundary shape. If they are available, other experimental data can also be incorporated into the analysis method. A set of data from the TEXTOR tokamak reported by Soltwisch [3] is analyzed by the method, and the results are discussed.