Application of He I Line Intensity Ratio Method to Tokamak Plasma in TOKASTAR-2

抄録

Temporal evolution of electron density and temperature in TOKASTAR-2 tokamak plasma is obtained for the first time by He I line intensity ratio method. In the calculation of collisional radiative model, we consider the effect of radiation trapping and validity of quasi-steady-state approximation for metastable states. He I line intensities are measured using a monochromator that has a photomultiplier tube as a detector. To evaluate line intensity ratios used for analysis, their sensitivity factors for plasma parameters are newly introduced. We investigate plasma current I_p dependence of the electron density n_e and temperature T_e by changing the charging voltage of ohmic heating V_OH.The n_e depended on I_p independent of V_OH. The Spitzer resistance obtained from the measured T_e was consistent with the plasma resistance at I_p top phase.