The Alcator C-MOD control system

The computer-based portions of the Alcator C-MOD control system are described. The control system coordinates all C-MOD systems, including power, vacuum, heating and cooling, access control, plasma shape, and position control, and diagnostics. Programmable logic controllers (PLCs) are located near each subsystem. The control room is isolated by fiber optics. Functions that are essential to personnel or equipment safety are implemented in hardwired logic and monitored but not controlled by the PLCs. The initial configuration will include over 25 Allen-Bradley PLC-5 units. The PLCs in each subsystem are connected to personal computers (PCs) in the control room. The PCs provide graphical displays and operator interface. The PCs are networked and share process data with each other and with a master control console and a large mimic panel. During each shot, control of the power supply voltage programming will pass to a hybrid computer. The hybrid performs several matrix multiplications on the analog data using coefficients stored digitally and loaded prior to the pulse. Each set of coefficients provides control laws for a particular phase of the discharge. Any one of 400 sets of coefficients can be selected in less than 1 ms