X-mode broadband reflectometric density profile measurements on DIII-D

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Abstract
A 50–75 GHz, X‐mode, broadband reflectometer system is installed and operational on DIII‐D. Density profiles have been obtained under a wide range of operating conditions, including Ohmic, L‐, and H‐mode operation. Good agreement has been found with profiles obtained by Thomson scattering, but only with the use of fast sweeps. Profiles are calculated from the line‐integrated phase data using a stable numerical inversion algorithm. Using these techniques, and allowing for the reset time of the tube, density profiles can be measured every 2.5 ms. The system is still under development: By adding an additional 50–75 GHz BWO and mixers, the system will be reconfigured to also act as a correlation reflectometer.