The UCLA frequency tunable correlation reflectometer system on DIII-D.

A broadband tunable (∼50-75 GHz) correlation reflectometer system is installed and operational on the DIII-D tokamak. The same launch and receive horns are utilized for the two probing frequencies ensuring that they sample the same path within the plasma. Very wide band IF electronics allow the separation frequency to be continuously tuned over the range 100 MHz→10 GHz corresponding to a maximum spatial separation of ∼7 cm. Sweeping the separation frequency during the plasma shot produces multiple spatial points (>10) on a single discharge reducing shot to shot reproducibility problems and increasing the spatial resolution. A description of the microwave system, laboratory tests, and representative data from a tokamak discharge are presented. Difficulties with the method and some possible resolutions are discussed. [ABSTRACT FROM AUTHOR]