Ion temperature and plasma rotation velocity measurements using visible spectroscopy on TdeV

Abstract

A visible spectroscopic imaging system has been developed on Tokamak de Varennes (TdeV) that provides profile measurements of the ion temperature and plasma rotation velocity. Multiple poloidal and tangential chords were coupled to the entrance slit of a spectrometer equipped with a back-illuminated charge coupled device camera at its exit slit. The camera records spatially and spectrally resolved emission profiles with real time digitization and up to 70 ms/frame as temporal resolution. Line-integrated radiation from different ionization stages in the visible range (B V, C III, He II, and N IV) were chosen as representative of the plasma in their regions of maximum emission. Three types of plasma discharges are compared: ohmic and electron cyclotron resonance heated L and H modes. Preliminary results show that with an L–H transition, there is a 20%–30% increase of the ion temperature at midradius, without a pedestal and an increase of the toroidal velocity shear at r/a∼0.8.