Real-time digital control, data acquisition, and analysis system for the DIII-D multipulse Thomson scattering diagnostic

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Abstract
A VME‐based real‐time computer system for laser control, data acquisition, and analysis for the DIII‐D multipulse Thomson scattering diagnostic is described. The laser control task requires precise timing of up to eight Nd:YAG lasers, each with an average firing rate of 20 Hz. A cpu module in a real‐time multiprocessing computer system will operate the lasers with evenly staggered laser pulses or in a ‘‘burst mode,’’ where all available (fully charged) lasers can be fired at 50–100 μs intervals upon receipt of an external event trigger signal. One or more cpu modules, along with a LeCroy FERA (fast encoding and readout ADC) system, will perform real‐time data acquisition and analysis. Partial electron temperature and density profiles will be available for plasma feedback control within 1 ms following each laser pulse. The VME‐based computer system consists of two or more target processor modules (25 MHz Motorola 68030) running the VMEexec real‐time operating system connected to a Unix‐based host system (also a 68030). All real‐time software is fully interrupt driven to maximize system efficiency. Operator interaction and (non‐real‐time) data analysis takes place on a MicroVAX 3400 connected via DECnet.

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