Description
Real-time feedback control is a key enabling technology for stable, high-performance operation of the Wendelstein 7-X (W7-X) stellarator. The systems implemented so far allow precise regulation of essential plasma parameters, robust response to transient events, and reliable long-pulse operation across a wide range of magnetic configurations and plasma regimes. This summary provides an overview of the feedback control systems implemented and validated at W7-X, their technical realization, and their role in achieving stationary plasma scenarios.
All feedback systems are integrated into the W7-X segment control architecture and utilize a deterministic, Ethernet-based real-time network with millisecond-scale synchronization. Digital PID controllers form the backbone of all control loops, minimizing deviations between predefined setpoints and measured plasma parameters. Sensor signals are distributed via User Datagram Protocol (UDP) multicast, enabling coordinated multi-parameter control with low latency.
Implemented and validated feedback systems include control of electron density, total radiated power, sub-divertor neutral pressure, and total electron cyclotron resonance heating (ECRH) power.
Further developments include density control via ECRH power, pellet-based fueling control, neural-network-assisted gas injection for fueling and impurity seeding, and future efforts toward magnetic field and plasma profiles control. Together, these results demonstrate that real-time feedback control is a cornerstone of W7-X operation and provides a scalable foundation for advanced control strategies in future steady-state fusion devices.
This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 - EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.