Interprocess communication within the DIII-D plasma control system

The DIII-D tokamak fusion research experiment´s realtime digital plasma control system (PCS) is a complex and ever evolving system. During a plasma experiment, it is tasked with some of the most crucial functions at DIII-D. Key responsibilities of the PCS involve sub-system control, data acquisition/storage, and user interface. To accomplish these functions, the PCS is broken down into individual components (both software and hardware), each capable of handling a specific duty set. Constant interaction between these components is necessary prior, during and after a standard plasma cycle. Complicating the matter even more is that some components, mostly those which deal with user interaction, may exist remotely, that is to say they are not part of the immediate hardware which makes up the bulk of the PCS. The four main objectives of this paper are to 1) present a brief outline of the PCS hardware/software and how they relate to each other; 2) present a brief overview of a standard DIII-D plasma cycle (“a shot”); 3) using three sets of PCS sub-systems, describe in more detail the communication processes; 4) evaluate the benefits and drawbacks of said systems