Real-time feedback control of the radiation front location in the TCV tokamak

In the detached regime in tokamak divertors, an actuator, often local gas puffing, induces plasma power loss mechanisms, leading to a significant particle and heat flux reduction at the divertor target. Such a detached regime requires real-time plasma monitoring and control of the gas puff actuator. Many existing plasma diagnostics have a low signal-to-noise ratio in detached conditions and/or are not real-time. In this work, we apply real-time acquisition and processing techniques to C-III filtered images from multi-spectral imaging diagnostic MANTIS. The detected location of the C-III emission front is mapped to the poloidal plane using a non-tomographic approach. This emission front is a proxy of divertor cooling, making its deduced position a spatially distributed and attractive controllable quantity. For a dedicated discharge on TCV, we apply system identification to generate a data-driven dynamic model, describing the effect of divertor gas fueling on the emission front location. From this model, a feedback controller was synthesized off-line, and tested on TCV.