General Overview of the ITER Low Field Side Reflectometer Diagnostic System

Authors: A. Zolfaghari, M. Gomez, N. Allen, R. Feder, M. Messineo, H. Zhang

Abstract: The Low-Field- Side (LFS) Reflectometer is one of several reflectometer systems planned for ITER. The LFS Reflectometer microwaves reflecting off the O and Xmode cutoffs in the plasma, are used to probe the on and off-axis edge pedestal and scrape-off layer (SOL) electron density (ne) profiles. The LFS reflectometer will also be used for core MHD and turbulence measurements on ITER. The LFS system includes the antenna and transmission line for a Doppler reflectometer for turbulence rotation measurements. The front-end components of the LFS Reflectometer are housed in an equatorial port plug. The current LFS Reflectometer design contains 7 circular waveguides that function as both launch and receive antennas, with penetrations through the diagnostic first wall providing access to the plasma. The millimeter waves are coupled quasi-optically to the corresponding waveguides outside the vacuum through double quartz windows and quasi-optical Gaussian telescopes. The reference design features 7 broadband multimode corrugated circular waveguide transmission lines. The total length of the waveguide run from launch/receive horn to source/detector is approximately 40 meters. Details of the current mechanical, thermal and instrumentation design of the diagnostics system will be presented in this paper.

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