The run permit protection system for GTA

A Run Permit system has been designed for the Ground Test Accelerator (GTA). The system implements mode-dependent software interlocks to ensure proper operation of the accelerator, enabling the ion source extractor and RF systems when proper conditions are met. The system is implemented using the GTA control system; thus all information available to the control system is also available for use in interlock logic. The logic is defined in terms of control system channels, which reflect accelerator parameters such as actuator positions, power supply values, temperatures, etc. A mode switch in the control room selects the accelerator operating mode, for example injector only. The Run Permit software selects interlock logic as appropriate operating mode. This implementation easily accommodates logic changes as requirements evolve. To ensure reliable operation of a software-based system, a special circuit with a watch-dog timer is employed to produce the system's output signals. The software must periodically address the circuit, or the output signals are forced to a disabled state. For additional protection, there are self-test provisions for detecting and reacting to failures of the control system. (Author) 4 figs., ref