Operations of the External Conjugate‐T Matching System for the A2 ICRH Antennas at JET

The External Conjugate‐T (ECT) matching system was successfully commissioned on two A2 ICRH antennas at JET in 2009. The system allows trip‐free injection of RF power into ELMy H‐mode plasmas in the 32–52 MHz band without antenna phasing restrictions. The ECT demonstrates robust and predictable performance and high load‐tolerance during routine operations, injecting up to 4 MW average power into H‐mode plasma with Type‐I ELMs. The total power coupled to ELMy plasma by all the A2 antennas using the ECT and 3dB systems has been increased to 7 MW. Antenna arcing during ELMs has been identified as a new challenge to high‐power ICRH operations in H‐mode plasma. The implemented Advanced Wave Amplitude Comparison System (AWACS) has proven to be an efficient protection tool for the ECT scheme.