Experimental Results of the Novel 1.5-MW-Class 140-GHz Continuous-Wave Gyrotron for the Wendelstein 7-X Stellarator
Sergey Ponomarenko, H. P. Laqua, Konstantinos A. Avramidis, G. Gantenbein, Jérémy Gontard, Frank Hollmann, S. Illy, Zisis C. Ioannidis, John Jelonnek, J. Jin, Susanna Kohler, L. Krier, Alberto Leggieri, François Legrand, Gerald Lietaer, C. Liévin, S. Marsen, D. Moseev, F. Noke, T. Rzesnicki, T. Stange, M. Thumm, R. C. Wolf
Abstract
In this work, we present the achievements obtained during the commissioning phase of the newly developed 140-GHz continuous-wave tube TH1507U at the gyrotron test stand of the electron-cyclotron resonance heating facility of the Wendelstein 7-X stellarator. The gyrotron is based on the successful 1-MW class industrial TH1507 gyrotron, which operates in the TE<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{28},{8}}$ </tex-math></inline-formula> mode, and has been optimized for operation in the higher-order TE<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{28},{10}}$ </tex-math></inline-formula> mode. The 1-ms short-pulse tests confirmed the nominal output power of 1.5 MW. In a long-pulse operating regime, an output power of 1.3 MW with total efficiency 45.9% was demonstrated at pulse lengths of 3 minutes. Different regimes where the beam current is above 50 A demonstrated a saturation of output power at 1.3 MW, that can be explained by the presence of parasitic modes. A parasite-free operation with an output power of 1.2 MW was achieved with pulses up to 580 s in length. The pulse length was limited due to the existing capabilities of the cooling system at the test stand, and is foreseen to be extended in the future.