2021 Volume 16 Pages 2402029
Polarization of the hydrogen Lyman-α line is detected in the Large Helical Device. It is the first observation of a polarized atomic emission line in magnetically confined fusion plasma devices. With the help of an atomic model simulation, the anisotropy in the electron velocity distribution function (EVDF) in terms of T∥/T⊥ is evaluated, where T∥ and T⊥ represent the electron temperature in the parallel and perpendicular directions regarding the magnetic field, respectively. The results show that T∥/T⊥ has a tendency to decrease and deviate from unity with decreasing electron-electron collision frequency, which qualitatively agrees with an intuitive understanding of the anisotropic EVDF in the plasma boundary.
