  A load-tolerant External Conjugate-T (ECT) impedance matching system for two
A2 Ion Cyclotron Resonance Heating (ICRH) antennas has been successfully put
into operation at JET. The system allows continuous injection of the RF power
into plasma in the presence of strong antenna loading perturbations caused by
Edge Localized Modes (ELMs). Reliable ECT performance has been demonstrated
under a variety of antenna loading conditions including H-mode plasmas with
Radial Outer Gaps (ROG) in the range of 4-14 cm. The high resilience to ELMs
predicted during the circuit simulations has been fully confirmed
experimentally. Dedicated arc detection techniques and real-time matching
algorithms have been developed as a part of the ECT project. The new Advanced
Wave Amplitude Comparison System (AWACS) has proven highly efficient in
detection of arcs both between and during ELMs. The ECT system has allowed the
delivery of up to 4 MW of RF power without trips into plasmas with Type-I ELMs.
Together with the 3dB system and the ITER-Like Antenna (ILA), the ECT has
brought the total RF power coupled to ELMy plasma to over 8 MW, considerably
enhancing JET research capabilities. This paper provides an overview of the key
design features of the ECT system and summarizes the main experimental results
achieved so far.
