Experimental results and recent developments on the EU 2 MW 170 GHz coaxial cavity gyrotron for ITER

¹ Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), Association EURATOM-KIT, Kaiserstr. 12, D-76131 Karlsruhe, Germany
² Centre de Recherche en Physique des Plasmas (CRPP), Association Euratom-Confédération Suisse, EPFL Ecublens, Station 13, CH-1015 Lausanne, Switzerland
³ National Technical University of Athens (part of HELLAS), School of Electrical and Computer Engineering, 9 Iroon Polytechniou st., GR15773 Athens, Greece
⁴ National and Kapodistrian University of Athens (part of HELLAS), Faculty of Physics, 157 84 Athens, Greece.

^a e-mail: stefan.kern@kit.edu

Abstract

The European Gyrotron Consortium (EGYC) is responsible for developing one set of 170 GHz mm-wave sources, in support of Europe’s contribution to ITER. The original plan of targeting a 2 MW coaxial gyrotron is currently under discussion, in view of essential delays and damages. This paper reports on the latest results and plans with regard to the two 2 MW gyrotron prototypes, the industrial prototype at CRPP’s CW test stand and a modular pre-prototype at KIT. The industrial prototype was delivered to CRPP end of September 2011 and reached an output power of 2 MW at an efficiency of 45 % and with good RF beam pattern, in only four days of short pulse RF test. These results validated all design changes made in reaction to the results of the experiments in 2008. On the fifth experimental day, an internal absorber broke, terminating any further experiment with this tube. In parallel, design and experimental activities at KIT went on, in particular featuring reduced stray radiation down to 4% of the RF power. Next years’ plans for the 2 MW modular pre-prototype foresee a stepwise increase of pulse length.