Test of Phase Control and Impedance Matching of Dummy ICRF Antenna

We have installed HAS (HAndShake or HAsuu Seigyo: wave-number-control in Japanese) ICRF antennas in LHD from upper and lower ports, which are symmetrical antennas. The wave number parallel to the magnetic field line is controllable by adjusting the phase of the current on the straps for the variation of the experiments. Antenna impedance is not constant even if the plasma parameter remains constant when the complex current ratio is changed due to the mutual coupling between the two antennas. Reflection will increase unless tuners are adjusted. Figure 1 shows a schematic view of the antenna system including matching devices (liquid stub tuners). The two antennas are characterized by an impedance matrix, Za. Currents at the antenna ports of line 1 and 2 are identified as Ia1 and Ia2, respectively. Va1 and Va2 are the voltages at the antenna ports. These currents and voltages are related as follows: