Real-time reflectometry – An ASDEX Upgrade DCS plugin App for plasma position and shape feedback control

Abstract

O-mode microwave reflectometry will be used, on ITER and foreseeably on DEMO, to complement the standard magnetic diagnostics for plasma position control. With the preliminary design of ITER's plasma position reflectometers (PPR) presently underway, it is of the utmost interest to test beforehand all possible aspects of this future control application. ASDEX Upgrade (AUG) features a modern, modular and easily adaptable control system, and the only O-mode reflectometry setup capable of probing the plasma at two of the four lines of sight of ITER's PPR (gaps g3 and g6). After the first successful demonstration of plasma position control using reflectometry [1], the diagnostic's hardware was updated to acquire a higher number of signals and to improve its real time (RT) data-processing capabilities. Meanwhile, the system's software was rewritten to implement a pipelined architecture to improve its performance and deterministic behavior. The last stage of this pipeline, used to calculate the relevant control parameters, and synchronize and communicate with the discharge control system (DCS), now uses the new DCS software framework, appearing to the control infrastructure as a modular plug-in RT diagnostic App Process. Herein are discussed the adopted synchronization strategies as well as the gains obtained with this new software implementation, namely in terms of performance, fault tolerance, and measurement rate. Experimental data from control discharges is presented to illustrate the system's operational performance.