Radar arc and impairment detection and localization for the ITER ICRF antenna

A RAdar Arc and impairments Detection and localization (RAAD) system for the protection of high-power RF transmission lines components is presented. It offers several benefits over existing techniques. It can perform fast detection, localization, and classification of arcs and impairments/degradations along the full path of the RF power (in less than 5 us as required for the protection of ITER ICRF antenna). It also features completely independent operations from the RF power. The detection and monitoring of impairments/degradations enables the prevention of faults while the localization and classification of faults permits pinpoint maintenance operations. The RAAD system has been simulated in time domain adopting the Simulink tool, integrated into the complete ITER ICRF system (from the array antenna front-face up to the RF sources outputs, including the full transmission line and matching network). The radar signal is coupled into the transmission lines through a specifically designed coupling unit. Full wave simulations of the ITER ICRF system components have been performed in the radar bandwidth of operation, with and without arcs/impairments, to obtain S-matrices used in the time domain radar system simulations. All the arcs and impairments inserted in the components have been detected; the location obtained by the radar for each event has been compared to the one estimated analytically with excellent agreement. The radar simulations have demonstrated the ability to detect and localize arcs which cannot be detected by other systems such as low voltage arcs and series arcs. A solid solution, based on signal synchronization, for coping with high power interferences from ion cyclotron frequency harmonics in the radar bandwidth of operations has been implemented. Other events such as antenna load variations and matching elements modifications can be easily discriminated against arc events, being much slower than radar pulse repetition period. Next steps will be the implementation, testing and validation of a prototype of the complete RAAD system. This prototype will be tested on the ITER ICRF prototype antenna module and potentially on other operating ICRF installations.