Measurement of Anisotropic Electron Velocity Distribution Function in LHD by Polarization Spectroscopy

抄録

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.