Two-polarizer method for the pitch angle measurement of magnetic field in a toroidal plasma

Asymmetry of the motional Stark spectrum is caused by large angular divergence of an injected natural beam. To avoid this difficulty caused by the spectrum asymmetry, only the σ component is used to determine the pitch angle in the case of a high magnetic field with an optical system that contains two polarizers tilted ± 45° with respect to the horizontal direction. It is predicted that the pitch angle could be measured with an accuracy better than 0.2°.