US contributions to the development and calibration of quench detectors for the ITER QUELL

The ITER QUELL (quench experiment on long length) experiment calls for the development and demonstration of new methods of quench detection for cable in conduit (CIC) superconductors. These will directly monitor temperature and pressure changes within the CIC. The use of single mode optical fibers is being investigated for measurement of temperature during a quench. A full-length pressure sensor/switch consisting of two conducting strips enclosed in a flattened stainless steel capillary has also been developed. Above a threshold He pressure of about 1 MPa, tube walls will deflect enough to short the otherwise open strips to trigger a current relay switch and also reflect microwave pulses that are generated at the strips ends. These signals can independently indicate the occurrence and the location of a quench. These new sensors will be integrated with more conventional instruments which include co-wound insulated voltage sensors placed inside the CIC, strain gauge pressure transducers, and flowmeters to measure quench parameters.>