Experimental Testing of the European TH1509U 170-GHz 1-MW CW Industrial Gyrotron – Long Pulse Operation

The upgraded European 1-MW, 170-GHz continuous wave (CW) industrial prototype gyrotron (TH1509U) for electron cyclotron resonance heating and current drive in ITER was tested at the Karlsruhe Institute of Technology (KIT). In this work, we report on the major achievements during the experimental campaigns that took place intermittently between October 2020 and July 2021. The upgraded gyrotron clearly surpassed the performance of the previous TH1509 tube. In particular, TH1509U delivered (i) 0.9 MW in 180 s pulses (maximum possible pulse length with the KIT test stand) and (ii) more than 1 MW at a pulse length limited to 40 s, due to an unforeseen problem with the test stand cooling circuit at that time. In addition, it was possible to also demonstrate gyrotron operation at (iii) 0.5 MW in 1600 s pulses. The experiments will be continued at the FALCON test stand at the École Polytechnique Fédérale de Lausanne (EPFL)

The ECRH-Power Upgrade at the Wendelstein 7-X Stellarator

The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to other large fusion experiments, W7-X has a relatively low power-to-volume ratio. However high heating power is particularly necessary for achieving high plasma beta values, where the improved confinement of fast ions, one of the optimization criteria of W7-X, can be examined. It is therefore necessary to expand the ECRH systems in several consecutive steps. It is planned to increase the number of gyrotron positions from 10 to 12 and at the same time to evolve the gyrotron output power in several development steps from 1 MW to nominal 1.5 MW and, finally, up to 2 MW. At the same time, the transmission lines will also be upgraded for 2 MW operation. A special effort is also made to improve the reliability of the system by the fast control system

Recent experiments with the European 1MW, 170GHz industrial CW and short-pulse gyrotrons for ITER

The European Gyrotron Consortium (EGYC) is developing the European 1 MW, 170 GHz Continuous Wave (CW) industrial prototype gyrotron for ITER in cooperation with Thales Electron Devices (TED) and Fusion for Energy (F4E). This conventional, hollow-cavity gyrotron, is based on the 1 MW, 170 GHz Short-Pulse (SP) modular gyrotron that has been designed and manufactured by the Karlsruhe Institute of Technology (KIT) in collaboration with TED. Both gyrotrons have been tested successfully in multiple experiments. In this work we briefly report on the results with the CW gyrotron at KIT and we focus at the experiments at the Swiss Plasma Center (SPC). In addition, we present preliminary results from various upgrades of the SP tube that are currently tested at KIT

Conceptual design of a modular EC system for EU-Demo

The DEMO reactor studies within EUROfusion aim to develop a fusion power plant concept. The large Tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) Heating system with up to 130 MW foreseen to reach different regions of plasma for heating, suppression of instabilities and possibly supporting ramp-up and ramp-down phases. The present conceptual design of the system is based on 2-MW coaxial-cavity gyrotron sources in development at IHM-KIT, a transmission line using both circular corrugated waveguides and a quasi-optical evacuated multi-beam transmission line, and mirror antennas located in the Equatorial port. In order to have a modular system, the sources are grouped in “clusters”, which power is combined in the quasi-optical transmission line, up to the Tokamak Building, where they are split and routed as single waveguides. In the launcher, they are combined together again on the launching mirrors, to save space for the apertures in the Breeding Blanket. The present EC system has a certain flexibility to adapt to changing design guidelines, as the foreseen transition to a lower DEMO aspect ratio. The system and the development status of each subsystem will be presented

Status and future development of Heating and Current Drive for the EU DEMO

The European DEMO is a pulsed device with pulse length of 2 hours. The functions devoted to the heating and current drive system are: plasma breakdown, plasma ramp-up to the flat-top where fusion reactions occur, the control of the plasma during the flat-top phase, and finally the plasma ramp-down. The EU-DEMO project was in a Pre-Concept Design Phase during 2014-2020, meaning that in some cases, the design values of the device and the precise requirements from the physics point of view were not yet frozen. A total of 130 MW was considered for the all phases of the plasma: in the flat top, 30 MW is required for neoclassical tearing modes (NTM) control, 30 MW for burn control, and 70 MW for the control of thermal instability (TI), without any specific functions requested from each system, Electron Cyclotron (EC), Ion Cyclotron (IC), or Neutral Beam (NB) Injection. At the beginning of 2020, a strategic decision was taken, to consider EC as the baseline for the next phase (in 2021 and beyond). R&D on IC and NB will be risk mitigation measures. In parallel with progresses in Physics modelling, a decision point on the heating strategy will be taken by 2024. This paper describes the status of the R&D development during the period 2014-2020. It assumes that the 3 systems EC, IC and NB will be needed. For integration studies, they are assumed to be implemented at a power level of at least 50 MW. This paper describes in detail the status reached by the EC, IC and NB at the end of 2020. It will be used in the future for further development of the baseline heating method EC, and serves as starting point to further develop IC and NB in areas needed for these systems to be considered for DEMO

Status and future development of Heating and Current Drive for the EU DEMO

The European DEMO is a pulsed device with pulse length of 2 hours. The functions devoted to the heating and current drive system are: plasma breakdown, plasma ramp-up to the flat-top where fusion reactions occur, the control of the plasma during the flat-top phase, and finally the plasma ramp-down. The EU-DEMO project was in a Pre-Concept Design Phase during 2014-2020, meaning that in some cases, the design values of the device and the precise requirements from the physics point of view were not yet frozen. A total of 130 MW was considered for the all phases of the plasma: in the flat top, 30 MW is required for neoclassical tearing modes (NTM) control, 30 MW for burn control, and 70 MW for the control of thermal instability (TI), without any specific functions requested from each system, Electron Cyclotron (EC), Ion Cyclotron (IC), or Neutral Beam (NB) Injection. At the beginning of 2020, a strategic decision was taken, to consider EC as the baseline for the next phase (in 2021 and beyond). R&D on IC and NB will be risk mitigation measures. In parallel with progresses in Physics modelling, a decision point on the heating strategy will be taken by 2024. This paper describes the status of the R&D development during the period 2014-2020. It assumes that the 3 systems EC, IC and NB will be needed. For integration studies, they are assumed to be implemented at a power level of at least 50 MW. This paper describes in detail the status reached by the EC, IC and NB at the end of 2020. It will be used in the future for further development of the baseline heating method EC, and serves as starting point to further develop IC and NB in areas needed for these systems to be considered for DEMO