The real-time protection system for MAST-U

Abstract

The Mega Amp Spherical Tokamak (MAST) is currently being extensively upgraded to provide increased coil system and power supply capability to the extent certain combinations of currents could cause catastrophic damage. To ensure operation of MAST-U within safe engineering limits, the machine protection system was also updated. The protection system is needed to protect against coil faults (such as flashovers) and monitor and calculate, in real-time, quantities such as coil currents, axial coil forces and the stored energy within the coils. The Real-Time Protection System was developed and uses Field Programmable Gate Arrays (FPGAs) which monitors up to 89 different signals collected from 7 different locations around MAST-U at a rate of 0.5MS/s. It filters and calibrates the signals and performs calculations to check if these signals correspond to valid operating ranges for currents, stored energy and coil forces. If thresholds are exceeded, then several actions can be carried out including stops to specific power supplies or a more gradual stop from the plasma control system. Initial testing of the system has shown it meets this challenging specification and the system is able to react within 200μs to breaches in thresholds as well as collecting 400MB/s of calibrated and calculated data.