Hybrid Couplers On The JET ICRF System: Commissioning And First Results on ELMs

摘要

During the 2004-2005 shutdown, hybrid 3 dB couplers were installed between the A2 ICRF antennas A and B. The goal was to free one of the generators to power the new ITER-like ICRF antenna, but also to use the coupler properties to increase the ICRF power on ELMs. Furthermore, the fast data acquisition system was upgraded in order to monitor the forward and reflected voltage amplitudes with a time resolution up to 4 μs. As expected, the first tests showed that the reflected powers during ELMs was successfully directed to the coupler dummy load instead of the generators and that a clear improvement in the averaged coupled power in the presence of the ELMs could be obtained. However, the existing levels of the VSWR protection against arcs appeared not satisfactory for ELM-tolerant operation and had to be re-assessed. Moreover, evidence of parasitic low-VSWR activity in the vacuum transmission lines was found, emphasizing the importance of developing VSWR independent arc detection systems.