SUPERSONIC HELIUM BEAM FOR MEASUREMENT OF ELECTRIC-FIELD IN TORUS PLASMA EDGES

Numerical investigations on the basis of a collisional-radiative model have been made on the measurement of the electric field in torus plas ma edges using a supersonic helium beam with aid of laser excitation. In this simulation, the laser-induced fluorescence intensity of the He I 492.2 nm line associated with the forbidden excitation due to the S tark effect is estimated as a function of electric field strength. The results show that an electric field as low as 50 V cm(-1) can be meas ured by the supersonic beam with sufficient beam density (about 10(12) cm(-3)). A numerical discussion is also given on the measurement of t he electron temperature and density. (C) 1997 Elsevier Science S.A.