Plasma electron density measurements by the laser- and collision-induced fluorescence method

A new method based on the laser-induced fluorescence method has been developed to measure the spatial electron density distribution in plasmas. The local electron density can be determined by observing the intensity ratio of the laser- to the collision-induced fluorescence. A spatial electron density distribution of a helium plasma (T e approximately 6 eV, n e :10 11-12 cm -3 ) has been determined by observing the He(3 1 P to 2 1 S) laser-induced fluorescence and the He(3 1 D to 2 1 P) collision-induced fluorescence resulting from the He(3 1 P to 3 1 D) process due to collisions with electrons. The comparison of the result with that of a conventional method proves this new method is of practical use in the space-resolved measurements of plasma electron density.