Analysis of an actively-cooled coaxial cavity in a 170 GHz 2 MW gyrotron using the multi-physics computational tool MUCCA

• Published in: Fusion engineering and design Vol. 146; pp. 74 - 77
• Main Authors: Bertinetti, A., Albajar, F., Avramidis, K.A., Cau, F., Cismondi, F., Gantenbein, G., Jelonnek, J., Kalaria, P.C., Ruess, S., Rzesnicki, T., Savoldi, L., Zanino, R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2019; Elsevier Science Ltd
• Subjects: Coaxial cavity; Computer simulation; Continuous radiation; Cooling; Cyclotron resonance; Cyclotron resonance devices; Dynamic models; Electron cyclotron resonance; Electron Cyclotron Resonance Heating and Current Drive (ECRH&CD); Evolution; Fusion reactors; Gyrotron; Multi-physics; Simulation; Software; Temperature dependence; Upgrading; Multi-physics; Electron Cyclotron Resonance Heating and Current Drive (ECRH&CD); Simulation; Gyrotron; Coaxial cavity
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2018.11.033

•The refrigeration of a gyrotron coaxial cavity is investigated.•Annular cooling channel allows operation below T limit for ∼150 ms.•Steady state condition reached in the simulation after ∼ 3 s.•Mini-channels cooling configuration reduces T peak by ∼ 150 °C. Continuous Wave gyrotrons are the key elements for Electron Cyclotron Resonance Heating and Current Drive (ECRH&CD) in present fusion experiments and future fusion reactors. In the frame of the EUROfusion activities, a 170 GHz, 2 MW short-pulse (∼ 1 ms), water-cooled coaxial gyrotron, already tested at Karlsruhe Institute of Technology (KIT), is being upgraded for operation at longer pulses (∼ 100–1000 ms). Here we use the MUlti-physiCs tool for the integrated simulation of the CAvity (MUCCA), recently developed in collaboration between Politecnico di Torino and KIT, to analyze the evolution of the operating condition of the coaxial gyrotron cavity, self-consistently coupling thermal-hydraulic, thermo-mechanical and electro-dynamic models. The main results are presented in terms of evolution of temperature, heat load and deformation of the heated surface of the resonator and of the coaxial insert during the first few seconds of operation. We show that the system evolves towards stable operating conditions (no beam loss), with a peak temperature strongly dependent on the cooling configuration, where a large room for the improvement of the current cavity cooling design is found.