Development of advanced mini-channel cavity cooling systems for a 170 GHz, 2 MW coaxial cavity gyrotron

For Electron Cyclotron Heating and Current Drive (ECRH&CD) applications in fusion facilities, high-frequency (> 100 GHz), high-power (~ 1 – 2 MW) gyrotrons need to operate in long pulse regime (seconds to hours). In such conditions, the maximum heat-load on the wall of the interaction section is in the order of 2 kW/cm2, which is the major limiting technological factor for output power, efficiency and pulse-length of the tube. Considering long-pulse gyrotron operating, the thermal deformation due to cavity-wall heating also leads to a downshift of the gyrotron operating frequency [1]. Consequently, an effective cavity cooling system is a prerequisite to maintain the cavity temperature within material strength limits (e.g. 250°C for Glidcop). The ongoing gyrotron development demands a very effective cavity cooling system for stable and optimum gyrotron operation. Initially, the performance of the existing annular-gap cavity cooling system for the modular KIT 170 GHz, 2 MW coaxial cavity gyrotron were systematically studied in [2-3] and the simulation results suggest safe operation up to a pulse length of 150 ms. Hence, a very effective cavity cooling system is mandatory to increase the pulse-length and to improve gyrotron performance. ... mehrIn this work, the thermal performance of a mini-channel cavity cooling is numerically investigated and the influence of the various physical and operating parameters is systematically studied. To validate the simulations results, an in-house mock-up test set-up is also developed.
Possible exchange: A very effective cavity cooling is critical for the long-pulse, high-power gyrotron development in EU, US and Japan. The presented results of the Thermal-Hydraulic (TH) simulations of the mini-channel cooling system are promising. A joint investigation on the development of the mini-channel cavity cooling system will be fruitful. Additional ideas can be exchanged to further refine the simulation set-up. The simulation results could be verified with another multi-physics software. In later stage, the performance of the mini-channel cavity cooling system could be compared with the existing cavity cooling systems. It would be also interesting to discuss the possibilities for upgrading the existing cavity cooling mock-up test set-up.