Enhancement of the ASDEX Upgrade Real-Time Plasma Position Reflectometry Diagnostic

Microwave O-mode reflectometry is a diagnostic technique that will play an important supplementary role for plasma position control for ITER and foreseeably for DEMO. Density profiles from reflectometry will provide, at high temporal resolutions, estimates of the gap between the plasma magnetic separatrix and the tokamak vessel walls. These estimates will be used to detect and correct drifts in the magnetic gap measurements, the primary measurements used for plasma position and shape control. The feasibility of this alternative feedback control approach was demonstrated in 2011 on ASDEX Upgrade (AUG) [1], where the reflectometry gap estimate actually replaced the corresponding magnetic measurement in the position control loop. Presently, the AUG's real-time (RT) reflectometry diagnostic is being upgraded to improve not only its density range coverage but also its acquisition and RT data processing performance. The diagnostic is now capable of acquiring a total of 16 channels (previously 8) from both the high (HFS) and low field side (LFS) reflectometers, some of which are used in the RT density profile and separatrix gap calculations. The up-to-date characteristics of the new diagnostic server allow the implementation of new operation modes that exploit the very high data throughput (> 1.2 GB/s) of each of the two used acquisition boards. The ability to acquire data at rates higher than the control measurement rate (1 ms), for more detailed offline data processing, enables diagnostic operation in a mode identical to the one planned for the ITER plasma position reflectometer (PPR). Herein we will present the goals and characteristics of the newly upgraded AUG RT reflectometry diagnostic.