Coupling of electron cyclotron waves to the desired mode in plasma of HL-2A tokamak

3 MW/68 GHz electron cyclotron resonance heating and current driving systems have been developed on HL-2A tokamak and two new units which can operate at two frequencies, 140 GHz and 105 GHz are on-going. Dual-polarizers for changing of the polarization of the wave beam have been designed for these systems based on the integral method of diffraction gratings. Finally, coupling between the electron cyclotron waves and the plasma has been discussed and the results indicate that the desired mode can be obtained for all possible experiments associated with the electron cyclotron resonance heating and current driving systems on HL-2A.