Simple determination of electron densities in plasmas submitted to magnetic fields

A method is described to measure electron densities in plasmas with a sufficiently strong magnetic field superposed. The profiles of the spectral lines emitted by such a plasma are shaped by the Stark and Zeeman effect (Lorentz-triplet). Eliminating the central Zeeman component by a polarizer or observing in field direction, one gets a doublet, in which for a given spectral line and magnetic field strength the ratioI ₀/I _z of minimum to maximum intensities is only a function of the electron density. Measuring this ratio one finds the corresponding densities by means of calibration curves given below for the He I lineλ=5876 å. This calibration is independent of the spectral arrangement, when utilizing a polarizer for the spectral observation.