Evaluation of the Backup Signal-processing System of the KSTAR Quench Detection System

The Quench Detection System (QDS) of the Korea Superconducting Tokamak Advanced Research (KSTAR) has been operated to prevent from overheating the superconducting coil system for 11 years. The QDS discriminates a normal voltage of ∼100 mV on NbTi or Nb3Sn cable-in-conduit conductors in the event of quench, while the Poloidal Field coils are applied with voltages of up to some kV by pulsed operation of the magnet power supply system. Three VME systems (VMEs) are used to compensate remaining induced voltage in the quench detection signals; however, products of the VMEs are probably discontinued on the global markets before the end of the KSTAR project. Accordingly a Backup Signal-processing System (BSS) is being developed and tested by mostly using generic and reliable commercial-off-the-shelf devices. The BSS is designed to replicate all the logical functions of the VMEs, and conducts quench detection by using FPGAs; whereas, the VMEs are using CPUs. Both the VMEs and the BSS simultaneously operate to detect quench, and quench alarms are voted by 1-out-of-2 logic to generate interlock signals in normal operation. A subset of the BSS integrated with the QDS has demonstrated expected performances in the KSTAR campaign 2018.