CALIBRATION OF THE UPGRADED MOTIONAL STARK-EFFECT DIAGNOSTIC ON TFTR

The q profile plays a key role for plasma equilibrium and theories of magnetohydrodynamic instabilities. With the development of the motiona l Stark effect (MSE) diagnostic, accurate q(r,t) profiles have been me asured and utilized for equilibrium and stability analysis. Improvemen ts to the MSE diagnostic on TFTR include a new method for calibrating the system and increasing the number of sightlines from 12 to 21 chann els. A technique that uses the known poloidal field at the edge of the plasma is utilized to calibrate each sightline. The major radius is m oved over the course of a discharge such that the plasma edge covers e ach sightline radius. Then with several discharges at various plasma c urrents each channel is independently calibrated. This method has been compared to our earlier calibration technique using neutral beam inje ction into a gas filled torus and some differences in the calibration have been found that have been attributed to differences in the excita tion and l mixing processes in the Stark spectrum. (C) 1997 American I nstitute of Physics.