Design optimization for the quench protection of DTT's superconducting toroidal field magnets

The paper is focused on the optimal design of Fast Discharge Unit (FDU) for the quench protection of the Toroidal Field (TF) magnets of the Divertor Tokamak Test facility (DTT), an experimental facility under construction in ENEA Frascati Research Centre (Rome, Italy). The FDU is a safety key component that protects the superconducting magnets when a quench is detected through the fast extraction of the energy stored in the magnets by adding a discharge dump resistor (DR) in the TF magnets circuit. A comparison between a fixed DR and a switched variable DR has been implemented by changing resistor parameters and by using multiple current control of the power electronics components (IGCTs). The new configuration allows to reduce the maximum voltage and the thermal stresses both for superconducting magnets and for FDUs (Fast Discharge Units), so reducing the insulation level of all TF (Toroidal Field) coil circuits, including also the power supply, reducing the hotspot temperature on the TF coils and the specific energy through them. Another advantage of the proposed configuration is the reduction of the size of all electrical devices of TF coil circuits so achieving a more effective and reliable design, also decreasing the overall costs.