Key aspects of an EC system of a fusion plant are the performance and reliability of megawatt-class long-pulse and continuous-wave (CW) gyrotrons. Both aspects rely on the robust technical design of the gyrotron tube and its integration with the building and EC plant auxiliaries.
The EU gyrotron for ITER (170 GHz, 1 MW CW) was designed within EGYC (European GYrotron Consortium) in collaboration with the industrial partner Thales under the coordination of Fusion for Energy (F4E). Following a low-risk approach, the design of the ITER gyrotron was based on the unique expertise in EU in the series production of high-power and long-pulse gyrotrons for the W7-X Stellarator.
The focus of the technical design of the gyrotron was on the enhancement of the tube reliability, provided for instance by the excellent ultra-high vacuum capabilities, the sufficient margin for collector heat dissipation, the specific calorimetry of the main subassemblies, the temperature monitoring of critical parts, and the low-pressure drop of the cooling circuits. At the same time, Thales adopted important features regarding personal safety, such as the grounded metallic envelope of the tube and the full X-rays shielding protection. Moreover, this gyrotron offers superior installation and operational flexibility thanks to the use of automatic HV connectors, the different operating points with equivalent performance at higher and lower voltages and currents, the robust cathode design concept allowing fast current ramp-ups, and the low sensitivity of the output performance to different type of loads.
In this paper, the inherent gyrotron tube design features enhancing reliability, safety and operational flexibility will be described. In addition, the essential modelling, analysis and qualification actions taken to secure industrialization and series production will be presented, such as the development of a consistent suite of simulations tools for design and interpretation of results, the thermal-hydraulic analyses of high-heat flux parts, the qualification of gun manufacturing technologies, the assessment of tolerances and advanced metrology controls, the control of dielectric and mechanical material properties of ceramics, and the procedure of low-power verifications of quasi-optical converter system.
Finally, the results of the important efforts made to optimize the design of the gyrotron auxiliaries to the ITER environment will be presented, such as HV configuration and EMC enhancement measures. Most of these features have been verified with the 2016 and 2018 tests of the EU gyrotron prototype at the EU EC tests stands of KIT and SPC. After some further improvement actions, the EU gyrotron prototype will be tested again in 2020.
The views expressed do not necessarily reflect those of the ITER Organization and Fusion for Energy (F4E). Neither F4E nor any person acting on behalf of F4Eis responsible for the use, which might be made of the information in this publication.
|Affiliation||Fusion for Energy|
|Country or International Organization||Fusion for Energy|