Design and implementation of a control system for a deuterium pellet injector

The Oak Ridge National Laboratory is currently developing a deuterium pellet injector for installation on the tokamak fusion test reactor (TFTR). This paper describes the design and development of a stand‐alone data acquisition and control system for that device. Major elements of the hardware are an Allen–Bradley PLC 2/30 programmable logic controller, a MicroVAX‐II computer using the VMS operating system, CAMAC data acquisition and communication equipment, and special‐purpose controllers for temperature and for the sequencing of pellet firing valves. The PLC performs all actual control actions and acquires data pertinent to those actions. The MicroVAX receives the data acquired by the PLC, displays it for the operator, prompts for and processes requests for action from the operator, and informs the PLC of those requests. The primary purpose of this paper is to describe the software operating in the MicroVAX, including the system architecture, major tasks, and ancillary and background tasks.