Multi-Channel Microwave Reflectometer with Fermi Antenna Receivers

Abstract

We have evaluated a Fermi antenna newly designed in X band for use in a multichannel reflectometer. The advantages of the Fermi antenna are that it can be adopted as an array antenna owing to its planer shape and fabricated with a low cost due to its compactness and a light-weighted structure. The radiation-beam widths in the E- and H-plane are almost equal to each other and the side-lobe levels are low. Plasma behaviors in the HITOP device are measured by reflectometry using two Fermi antenna receivers. Time evolution of the cutoff layer and plasma rotation velocity measured by the reflectometer are in good agreement with an electrostatic probe measurement.