IMPROVED OPERATION OF THE MICHELSON INTERFEROMETER ELECTRON-CYCLOTRONEMISSION DIAGNOSTIC ON DIII-D

The measurement of accurate temperature profiles is critical for trans port analysis and equilibrium reconstruction in the DIII-D tokamak. Re cent refinements in the Michelson interferometer diagnostic have produ ced more precise electron temperature measurements from electron cyclo tron emission and made them available for a wider range of discharge c onditions. Replacement of a lens-relay with a low-loss corrugated wave guide transmission system resulted in an increase in throughput of 6 d B and a reduction of calibration error from 15% to 5%. The waveguide e xhibits a small polarization scrambling fraction of 0.05 at the quarte r-wavelength frequency and very stable transmission characteristics ov er time. Further reduction in error was realized through special signa l processing of the calibration and plasma interferograms. (C) 1997 Am erican Institute of Physics.