Millimeter wave polarimeter for characterizing high-power plasma heating systems

We have built a millimeter wave polarimeter which measures wave polarizatio n parameters: the polarization angle, and the ellipticity including field s pin direction in an evacuated high-power system. The polarimeter was applie d to diagnose the 1 MW level electron-cyclotron plasma heating system at 11 0 GHz for the DIII-D tokamak. We have observed the time-dependent behavior of the gyrotrons and have characterized and calibrated the high-power trans mission system which consists of grooved mirror polarizers, miter bends, sw itches, and corrugated wave guides. This article describes the principle of operation and the design method of the polarimeter and the examples of mea surements. (C) 1999 American Institute of Physics. [S0034-6748(99)00104-5].