RF Arc Detection in ICRH RDL Antennas by Phase Measurement.

A voltage breakdown in an Ion Cyclotron Resonance Heating (ICRH) system is usually detected as an abrupt change in the module of the reflection coefficient |Γin| at the power source output. The same effect can be due to a large load variation. This study is carried out by constructing a electrical model for a Tore Supra ITER-like antenna (TS ILA) [1], and to analyse how a voltage breakdown, localized in any part of the system, modifies several electrical parameters of the circuit (with respect to perfect match conditions), as detected at the location of the monitoring points. The phase difference between the reflections coefficients measured at the output of tuning network when an arc strikes in one of two Resonant double loop (RDL) sections of the ICRH TS ILA appears to be the most promising parameter to detect the arc and identify its position. It is also significantly insensitive to a load variation so an arc and edge localized modes (ELMs) can be distinguished. [ABSTRACT FROM AUTHOR]