Theoretical Study on the Operation of the EU/KIT TE34,19-Mode Coaxial-Cavity Gyrotron at 170/204/238 GHz

Abstract

The 170 GHz 2 MW TE34,19-mode coaxial-cavity modular short-pulse pre-prototype gyrotron at KIT was recently modified in order to verify the multi-megawatt coaxial-cavity technology at longer pulses. In parallel, theoretical investigations on a possibility to operate the 170 GHz TE34,19-mode coaxial-cavity prototype at multiple frequencies up to 238 GHz have been started, with a goal to find a configuration at which the tube could operate in the KIT FULGOR gyrotron test facility using the new 10.5 T SC magnet. This paper indicates which adjustments have to be made and show the feasibility of the multi-frequency operation. Small modifications at the gyrotron cavity will support an RF output power of more than 2 MW at 170/204 GHz. Furthermore, a new gyrotron launcher has been designed capable of producing a Gaussian microwave beam with a Gaussian mode content of more than 96% at these frequencies.

Overview of recent gyrotron R&D towards DEMO within EUROfusion Work Package Heating and Current Drive

“…To keep the development path towards the DEMO gyrotron as fast and cost-effective as possible, the design of a 2 MW, 170/204 GHz coaxial gyrotron has been initiated using the existing 170 GHz coaxial gyrotron as starting point [19][20]. The simulation results show that a good performance can already be achieved with only minor modifications of the existing modular gyrotron.…”

“…To keep the development path towards the DEMO gyrotron as fast and cost-effective as possible, the design of a 2 MW, 170/204 GHz coaxial gyrotron has been initiated using the existing 170 GHz coaxial gyrotron at KIT as starting point [30,31]. According to the EU DEMO physics baseline [10], the frequencies for heating and current drive are ~165 GHz and ~200 GHz, respectively.…”

Design of a Quasi-Optical Mode Converter for a Dual-Frequency Coaxial-Cavity Gyrotron

“…Operating in the TE34,19 mode, both the simulation and the experimental results show very high Gaussian-mode contents of the RF beam at the output window, namely 96.3% and 96%, respectively [4,5]. Currently the existing short pulse modular pre-prototype gyrotron is being upgraded towards an additional operation at 204 GHz [6]. Considering the TE34,19 mode at 170 GHz, the TE40,23 mode is selected for the operation at 204 GHz.…”

Operating the KIT 170 GHz 2 MW Coaxial-Cavity Gyrotron at 204 GHz: Performance Expectations and First Cold Test of the Quasi-Optical System

“…Recently, the KIT 170 GHz TE34,19-mode coaxial-cavity pre-prototype, which delivers an RF output power of more than 2 MW in short-pulse operation [4], has been modified towards longer-pulse operation of up to 100 ms, in a first step [5]. In parallel, the modular shortpulse coaxial-cavity pre-prototype is being upgraded towards dual-or even triple frequency operation [6]. The design of this multi-frequency gyrotron is on the basis of the existing TE34,19mode coaxial-cavity gyrotron.…”