A plasma discharge fast control system for large fusion reactors

In ENEA Frascati research centre an experimental fusion machine called Frascati Tokamak Upgrade (FTU) is in operation since 1990. The plasma discharge phase of FTU is driven by the dedicated system FSC-U (Fast Sequence Control upgraded), which has been developed in order to send all the necessary commands to the power plants, feeding the toroidal and poloidal coils during the plasma discharge, meanwhile controlling the correct outcome and recording all the events with time resolution of the order of 20 microseconds. In case of incorrect execution of the sequence the system is able to safely shutdown the plants and the plasma pulse. The present FSC-U system is based on an up to date, off the shelf, hardware platform, and it is equipped with an integrated configurator and a custom command and control sequence programming language, allowing the user to program the sequences by linking the execution times of the commands and of the state verifications each other or to global time parameters. The FSC-U system has been tailored to the I/O FTU needs and time scale, but was conceived with the aim of more powerful up-grades. Now is well in progress a design phase in order to extend the system, increasing of many times the system IO capability and, above all, reaching time resolution of one microsecond. The FSC-U system is a command sequencer that include also some functions and concepts of the interlock and protection system, in the new design this functionality was further enhanced in order to comply with the more demanding applications of the large fusion reactors.