Large coil task instrumentation and diagnostics

The goal of the Large Coil Task (LCT) was to develop large toroidal superconducting magnets for fusion reactors. Each of the six coils built for this task was heavily instrumented with some 200 to 400 sensors and diagnostic voltage taps to test its performance and characteristics. In addition, more than a thousand sensors were installed in the facility and test-stand components to ensure safe and controlled operation. Through the three-year test period, some sensors worked consistently, some failed prematurely, some constantly gave useful information, some were rarely used, and others were vital in a particular test mode. This paper reviews the various type of thermometers, pressure transducers, flowmeters, strain gages, displacement transducers, acoustic emission sensors, field probes, and other diagnostic instrumentation used in LCT. The usefulness of the sensors, the difficulties with some of them, and the reliability of different groups of sensors in this task are described.