Measurement of electron temperature anisotropy in ohmically heated plasmas in TST-2 using a double-pass Thomson scattering system

Double-pass Thomson scattering (TS) is a technique used to measure electron temperature anisotropy, and a double-pass TS diagnostic system with good safety (avoidance of damage to the YAG laser device by the backward beam) and performance (collection optics with sufficient efficiency) was fabricated in TST-2. Obvious electron temperature anisotropies were found in the TST-2 ohmic plasmas. Moreover, a simple theoretical model was proposed to estimate the electron temperature anisotropy from the inductive electric field, the electron temperature and density, and the effective ionic charge. The measured electron temperature anisotropy shows a qualitative agreement with the theoretical one when we consider the factor of ambiguities in the electric field and the effective ionic charge.