Edge density profile measurements in TdeV using amplitude modulation reflectometry

A single channel AM reflectometer, operating in the frequency range of 33.0 less than or equal to f less than or equal to 50.0 GHz, has been developed to provide edge electron density profiles on TdeV. The X-mode cut-off layer, covering densities n(e) < 10(19) m(-3) for 1.5 T operation, is used to measure a portion of the plasma edge region 0.9 less than or equal to r/a less than or equal to 1.2. Briefly, our design consists in launching a microwave beam amplitude modulated at 201 MHz. The reflected wave is detected and downconverted to 1 MHz to facilitate filtering and phase detection. Finally, a linear phase detector compares the phase of the resulting signal (1 MHz) with that of the reference source. The design and construction of the reflectometer will be described and preliminary results presented. (C) 1997 American Institute of Physics.