First results from the MAST digital plasma control system

The mega-amp spherical tokamak (MAST) has operated under a new digital plasma control system [Fusion Eng. Des. 66–68 (2003) 761]. The new system, based on commercially available VME hardware, has replaced most of the old analogue control electronics [Fusion Eng. Des. 56–57 (2001) 749] with algorithms implemented in the control software. General Atomics provided their PCS [B.G. Penaflor, J.R. Ferron, M.L. Walker, A structured architecture for advanced plasma control experiments, in: Proceedings of the 19th SOFT, vol. 1, Lisbon, Portugal, 1996, p. 965] software infrastructure as a generic framework for a plasma control system. A powerful configuration tool has been developed to generate the MAST-specific code from a set of structured documents written in extensible mark-up language (XML). This enables rapid development of new control algorithms and permits safe re-configuration of the code layout, whilst maintaining the coherence of multiple cross-references. The initial algorithm set emulates the behaviour of the original analogue control hardware where it is sensible to do so, but implements several new plant protection capabilities that were previously too difficult to provide with analogue electronics. Shots previously run with the old system can be converted to run in the new system, thus allowing previous campaigns to be continued without the need to develop new scenarios. the present engineering break, a new suite of algorithms is being developed to provide plasma boundary reconstruction and control functions that fully exploit the capabilities of the digital system.