The Jet Lower Hybrid Current Drive Power and Phase Control

JET - the Joint European Torus - is a major experiment aimed at establishing the feasibility of using nuclear fusion as a source of energy in the 21st Century. In a fusion reactor a plasma current of several million amperes is induced by transformer action and a complex system of magnetic fields is used to confine the plasma away from the walls of the vacuum vessel. The aim of the JET Lower Hybrid Current Drive (LHCD) experiment is to drive a sizeable fraction of the plasma current by means of microwaves. A travelling wave launching structure consisting of a set of individual waveguide antennas must be accurately powered and phased in order to optimise the current drive mechanism. Various distortions must be corrected in real time in order to maintain the required phase pattern at the launching structure. This paper describes a system aimed at achieving these objectives.