Second harmonic protection filter circuits for the JET ICRF plant

The analysis of present day ICRF amplifiers and measurements carried out on TEXTORʹs ICRF system have revealed that without appropriate measures these systems are prone to spurious generation of power at the second harmonic frequency (F. Durodié, M. Vervier, Generation of harmonic frequencies and their effects in present day ICRF systems. 13th Topical Conference on Applications of radio Frequency Power to Plasmas, Annapolis, Maryland, USA, 12–14 April 1999.). This could lead either to erroneous activation of the reflected power safety protection or to highly increased voltages in the (unmatched) transmission lines and antennas. It could explain why arcs are not always found at the expected voltage maxima.