Progress on 140 GHz Gyrotron Development: Advancing Towards 2-MW Operation

Le résumé fourni par la source

This study presents the theoretical considerations made in frame of the development of a 2 MW conventional-cavity gyrotron, focusing on its engineering constraints and theoretical validation at the Karlsruhe Institute of Technology (KIT). The study includes initial analyses of a 140 GHz gyrotron for designed to deliver 2 MW output power in advanced electron cyclotron resonance heating (ECRH) systems for fusion devices. While this gyrotron is developed with a general applicability in mind, its specifications align with the potential upgrade of the ECRH system at the Wendelstein (W7-X) stellarator. This design aims for utilizing the existing infrastructure already operational for achieving 1.5 MW at W7-X. The present study includes mode selection, starting current, and time-dependent multi-mode calculations which are carried out to optimize gyrotron performance to achieve high output power considering kinetic electron energy of 88 keV, pitch factor of 1.3, electron beam radius of 10.1 mm with the approximation of 5 % velocity spread. The output power at the desired mode$\text{TE}_{28,12}$in the RF interaction cavity is confirmed by timedependent multi-mode simulations with an interaction efficiency of$>32 \%$. Considering a conductivity of$2.05 \times 10^{7} \mathrm{S} / \mathrm{m}$for Glidcop, surface roughness of 200 nm, and a temperature of 200° C, an output power of 2.2 MW is attained within the ohmic wall-loading limit of$2.2 \text{kW} / \text{cm}^{2}$. Further, with conductivity of$1.83 \times 10^{7} \mathrm{S} / \mathrm{m}$at surface roughness of 200 nm, and temperature of 250° C exceeded the ohmic wall-loading at an output power of 1.8 MW. By enhancing cavity cooling using advanced mini-channel cooling, which allows peak wall-loading of up to$2.5 \text{kW} / \text{cm}^{2}$, the potential to achieve output powers exceeding 2.4 MW at the end of the cavity becomes feasible. Additionally, optimizing the interaction cavity surface roughness can support higher conductivity, enabling high-output power with the existing Raschig Rings cooling system.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.