Beam profile measurements of the output microwave beam of 2MW/170GHz coaxial-cavity gyrotron for ITER

The first prototype of the European 170 GHz / 2 MW / CW coaxial cavity gyrotron is presently being tested in Lausanne. As a part of the experimental campaign, infrared measurements were performed at short pulse length for the characterization of the output microwave beam profile. For this purpose, an RF box was designed and used for IR measurements. The beam pattern was measured inside the box at several locations away from the window in a transverse plane perpendicular to the beam propagation direction. Three different materials Kapton / Robax / PVC were tested for the pattern measurement. The measured data will be used for the interpretation of the output microwave Gaussian beam by phase reconstruction and its higher order mode content analysis. Experimental results and phase reconstruction results along with an analysis of the higher order mode content of the output microwave Gaussian beam will be reported.