Description: This work represents an attempt to solve a fundamental problem with all coupling devices in tokamaks intended to launch waves in the ion cyclotron range of frequencies (ICRF), that of excessive voltage levels on the launcher and its feed lines. These voltages can lead to impurity problems in the plasma, and they determine the maximum power that can be coupled to the plasma, since it is when arcs caused by this voltage frequently occur that the power must be reduced. The approach taken is to consider an antenna which is composed of many smaller units, each operating at much lower voltages, stacked on end to provide the equivalent functionality of a conventional launcher. The work described herein involved designing, building, and operating such a launcher in the Phaedrus-T tokamak. The results showed that the antenna worked as expected, reducing the voltage dramatically, while still functioning property, and producing fewer impurity problems and no arcing. A design extrapolating the principles of this idea to reactor-sized tokamaks such as ITER was developed. In addition, a novel decoupling scheme was developed in order to adapt this antenna idea to low frequency current drive schemes.
Date: September 1, 1995
Creator: Probert, P.H.
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