Progress and plans for MAST plasma control

The initial control system for the Mega-Amp Spherical Tokamak (MAST) was assembled from existing analogue hardware modules to ensure a low-risk design. It has been used in the successful commissioning of the machine to plasma currents of over 1MA and pulse lengths of greater than 0.5 s. To aid in its design and evaluation, a SIMULINK model of the control system was developed and combined with a model of the MAST vessel, coils and all poloidal power systems. This is a useful tool for modelling the vacuum field for various start-up scenarios. It has also proved useful for validating the initial set-up of the control system, and having configured the feedback gains by simulation, no further changes were required for actual commissioning, which was completed rapidly. This present control system meets the requirements of the early physics programme of MAST, but later programmes will require more advanced control scenarios. For these requirements, a digital control system is planned as an upgrade.