Development of robust indicators for the identification of electron temperature profile anomalies and application to JET

Abstract

Recent experience with metallic devices operating in ITER relevant regions of the operational space, has shown that the disruptivity of these plasmas is unacceptably high. The main causes of the disruptions are linked to impurity accumulation in the core and edge cooling, resulting in unstable current profiles. Avoidance and prevention of the consequent instabilities require the early detection of anomalous electron temperature profiles. A series of indicators have been developed and their performances compared, to find the most suitable inputs for disruption predictors. Their properties are assessed on the basis of information content, reliability and real-time availability. The best performing ones provide much better results than the ones reported in the literature, as shown by both numerical tests with synthetic data and the analysis of experimental signals from JET with the ITER-like wall. They provide better accuracy, lower false alarms and earlier detection. The improved discriminatory capability of the developed indicators is expected to significantly improve the performance of the most advanced predictors recently reported in the literature.