Abstract
A number of reflectometer systems are under development on the DIII-D tokamak which are directly relevant to ITER needs and requirements. These include density profile measurement systems, a divertor reflectometer system, an inside launch reflectometer system for core access, and RF wave and edge density profile measurements at an ICRF antenna. For density profile measurements a new solid-state fast sweep FM reflectometer system has been installed on DIII-D. The faster sweep rates, combined with improved/optimal data processing routines developed over several years1,2 have resulted in more accurate profiles with improved time resolution, as required for routine operation on ITER. Also on DIII-D is an AM reflectometer system developed by ORNL which is being contrasted with the FM technique. A new reflectometer system is now operating in the lower divertor floor and is intended for peak density, density profile, and turbulence measurements. An inside launch reflectometer system has been upgraded for first tests of core profile measurements using the left hand X-mode cutoff. Use of the left hand cutoff and inside launch is necessary for core access for reflectometry on ITER.3 RF heating is also an option for ITER, and RF coupling/directionality depend on the position and details of the edge density profile. On DIII-D, reflectometry has provided detailed edge density profile measurements at the ICRF antenna. Also, a novel application of reflectometry on DIII-D has been the determination of the internal RF electric field profile in the plasma, which is related to the RF power deposition profile. Design and operational considerations as well as first data from the above systems are presented.
Published Version
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