Power Amplifiers with Reactance Steering Network for Efficient Driving of Variable Impedance Inductively Coupled Plasma Coils

This paper presents the design and implementation of a power amplifier system using reactance steering network for driving Inductively Coupled Plasma (ICP) coils in fusion reactors. The impedance of ICP coils can vary greatly depending on factors such as the plasma electron density, pressure or temperature of the plasma. The reactance steering network is used to reduce the range of this impedance variation and keep it within acceptable limits, such that the operational efficiency of the Class E power amplifiers driving the ICP coil through the reactance steering network is not adversely affected. A prototype with two equivalent resonant Class E power amplifiers, combined in parallel by a dedicated reactance steering network, to supply powers in excess of 200 W to a load mimicking the impedance characteristics of an ICP coil, is designed. The frequency of operation is set as 10 MHz. The simulation and experimental results both highlight the effectiveness of the reactance steering network when powering ICP coils using impedance sensitive resonant power amplifiers.