Microwave reflectometry for ICRF coupling studies on TFTR

A dual‐frequency differential‐phase reflectometer has been developed for use in ICRF power coupling studies on TFTR. This system has been optimized for measurements of the electron density profile in the edge‐gradient region, where density fluctuations are large. Initial proof‐of‐principle measurements demonstrate that this is an effective way to measure the electron density profile in the plasma‐edge region. A new reflectometer launcher is presently being installed on the center axis of the bay‐K ICRF antenna on TFTR, along with the associated waveguide transmission line. This will allow direct measurement of the edge‐density profile within the high‐power‐density environment of the ICRF antenna where density profile modification might be expected.