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

Abstract

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.

Overview on recent progress in magnetron injection gun theory and design for high power gyrotrons

“…Two design criteria have been determined for the suppression of the electron trapping mechanisms in MIG [11]: (i) the geometry of the MIG should be designed in such a way that the formation of potential wells is prevented, and (ii) no secondary electron emitted from the cathode surface is adiabatically trapped. These criteria have been considered for the design of the MIG of the refurbished first industrial prototype of the EU 170 GHz/2 MW coaxial cavity gyrotron project for ITER [12] and the MIG of the EU 170GHz/1 MW conventional cavity gyrotron for ITER [13]. The voltage standoff of both tubes was excellent, while during the operation of the gyrotrons no instability which could be correlated with the presence of trapped electrons was observed.…”

KIT coaxial gyrotron development: from ITER toward DEMO

“…In order to build-up a cost-effective pre-prototype gyrotron, the mirrors and the mirror box of the quasi-optical system are reused from the refurbished industrial coaxial-cavity gyrotron prototype [12, 13]. Nevertheless, slight modifications of the absorber ceramics, collector flanges, and window housing are necessary in order to satisfy the requirement of the modularity.…”

Development and Experimental Verification of an XY-Table for the Optimization of the Alignment of High-Power Gyrotrons

“…The axial misalignment of the electrons affects the operation of the gyrotron significantly. In particular, it is quite common that the starting currents of the modes will get higher [3]. In addition, the output power and the efficiency of the gyrotron drops [4], [5] not only because of the suboptimal coupling of the beam to the nominal mode but also due to the increased spread of the beam parameters [6], [7].…”