NSTX-U Digital Coil Protection System Integration with Existing Plasma Control System

The National Spherical Torus Experiment (NSTX) is currently finishing a multi-year upgrade (NSTX-U) that vastly increased the capabilities of the system. These upgrades required an improved coil protection system to prevent immediate damage as well as fatigue over time to the magnetic coils that control the plasma. Because the action taken by the DCPS affects many other systems, NSTX-U will additionally add a second DCPS with a modified failure path that operates with tighter limits. This second DCPS will execute the same algorithms, but will always trigger a fault first due to the difference in limit values. The action taken will be somewhat less drastic compared to the failure mode of the initial DCPS. The second DCPS runs the same protection algorithms, but does so using the Plasma Control System (PCS) computer and associated input data stream. The modularity of the DCPS framework allows a single pluggable software package to control the source of input data while keeping all remaining software functionality identical. The binary itself is compiled once yet runs in two physically separate computers using different limiting values, allowing not just reuse of code, but also reuse of validation and verification testing. This integration enables future direct coupling between the DCPS and PCS, and conceivably to other heterogeneous platforms as they become available.