ECE and reflectometric imaging on tokamak plasmas

Summary form only given. An exciting tool for the study and visualization of plasma turbulence is presently under development for the TEXTOR-94 tokamak. This system combines a high resolution electron cyclotron emission imaging (ECEI) diagnostic with an innovative microwave imaging reflectometer (MIR) diagnostic for the simultaneous localized measurement of electron temperature T. and electron density n/sub e/ fluctuations in the tokamak core. The ECEI diagnostic images second harmonic cyclotron radiation from the optically thick plasma onto a 1-D array, thereby forming an image of the T/sub e/ profile and fluctuations associated with the emission layer. The MIR diagnostic images radiation reflected from the plasma cutoff layer onto a similar 1-D array, thus forming an image of n/sub e/ fluctuations at the reflecting layer. Both diagnostics are capable of forming 2-D images of plasma turbulence by varying the frequency of the probing (for MIR) or received (for ECEI) signals. Adjustment of the reflectometer probing frequency permits the reflecting layer to be positioned coincident with the ECEI emission layer, thereby simultaneously sampling both T/sub e/ and n/sub e/ fluctuations over an extended surface of the TEXTOR-94 plasma. Such data will permit the visualization of complicated 2-D and/or 3-D structures which is essential for definitive comparisons to be made with the predictions of gyrokinetic computer simulations. In addition, the system will also be employed in the study of a number of MM phenomena such as plasma filament formation, magnetic islands and internal transport barriers. An overview of the simultaneous imaging diagnostic concept will be presented along with technical details and characterization measurements of the TEXTOR-94 diagnostic. The system is presently under fabrication, and will begin operation in August, 2002 when TEXTOR-94 resumes operation after the installation of a dynamic ergodic divertor.