Design of a Multijunction Antenna Unit for EAST Lower Hybrid Current Drive

A multijunction antenna unit has been designed and will be used to fabricate the new 4.6GHz Lower Hybrid Current Drive (LHCD) launcher for the long pulse operation of the Experimental Advanced Superconducting Tokamak (EAST). In this paper, the construction and design method of the multijunction antenna unit are described, and then the reflection coefficients of the unit with the matched load and with the plasma load are analyzed and discussed respectively by using High Frequency Structure Simulator (HFSS) code and by using numerical calculation based on linear coupling theory. The simulation result shows that the return loss of the antenna unit keeps below −25dB in a bandwidth of 100MHz and the power is distributed equally in the secondary waveguides of the unit. Numerical calculation result also shows that the unit has good coupling property in a wide range of tokamak plasma parameters.