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 plasma 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 Stark 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 measured by the supersonic beam with sufficient beam density (about 1012 cm−3). A numerical discussion is also given on the measurement of the electron temperature and density.