Development of a fast polarization spectroscopy technique for measurements of anisotropic electrons in ECR plasma start-up processes

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Anisotropy in the electron velocity distribution function (EVDF) can be deduced by using polarization in the atomic emission induced by the anisotropic electron-impact excitation. In this project, we have observed polarization in the lithium atom 2s-2p emission, which originates from the lithium atom beam injected into an electron cyclotron resonance plasma, and evaluated the kinetic energy and anisotropy in the motion of the electrons produced by the micro-wave heating. We have developed diagnostic systems to detect the polarization with spatial and temporal resolutions. By applying the developed diagnostic systems to plasmas produced in a cusp magnetic field, we have found electrons which move in direction perpendicular to the magnetic field in low electron density region. Anisotropy in the EVDF measured by a directional Langmuir probe is qualitatively consistent with the result of the polarization spectroscopy.