A coupling method of a gyrotron beam into a corrugated waveguide is proposed to achieve high HE{sub}11 mode purity in ITER'S ECH&CD transmission line. A matching optical unit (MOU) with two phase correcting mirrors is used. Each mirror is mounted on a goniometer stage for angle control. The mode content in the waveguide is measured for several sets of mirror angles to maximize the mode purity. The mode content is deduced using RF field profiles radiated from the waveguide outlet. A demonstrative procedure of the beam coupling achieved 93% of HE{sub}11 mode in the transmission power.
展开▼
