G. Aiello

First Operation of a Step-Frequency Tunable 1-MW Gyrotron With a Diamond Brewster Angle Output Window

Experimental results using a step-frequency tunable D-band gyrotron are reported. The short pulse (~3 ms) gyrotron is equipped with an elliptically brazed chemical vapor deposition (CVD) diamond Brewster angle output window. It is designed for the operation in the frequency range from 111.6 up to 165.7 GHz. Operating parameters for ten different frequencies corresponding to an equal number of different cavity operating modes has been measured. A minimum output power of 830 kW and a peak output power of 1.3 MW have been realized. For all frequencies, the parameters of the RF beam generated by the internal quasioptical converter, such as fundamental Gaussian contents and beam waist, are sufficiently good to allow an efficient coupling of the RF power out of the window. This is the first time a diamond Brewster angle window has been used in a high power gyrotron (~1 MW). Such a system offers the path to a simple and compact window solution for high power broadband applications using gyrotrons.

Objectives, physics requirements and conceptual design of an ECRH system for JET

A study has been conducted to evaluate the feasibility of installing an electron cyclotron resonance heating (ECRH) and current drive system on the JET tokamak. The main functions of this system would be electron heating, sawtooth control, neoclassical tearing mode control to access high beta regimes and current profile control to access and maintain advanced plasma scenarios. This paper presents an overview of the studies performed in this framework by an EU-Russia project team. The motivations for this major upgrade of the JET heating systems and the required functions are discussed. The main results of the study are summarized. The usefulness of a 10 MW level EC system for JET is definitely confirmed by the physics studies. Neither feasibility issues nor strong limitations for any of the functions envisaged have been found. This has led to a preliminary conceptual design of the system.

Preliminary design of the ITER ECH upper launcher

The design of the ITER electron cyclotron launchers recently reached the preliminary design level -the last major step before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20 MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one Equatorial Launcher for plasma heating and four Upper Launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle of the ULs allows to focus on magnetic islands which are expected on the rational magnetic flux surfaces q = 1 (sawtooth instability), q = 3/2 and q = 2 (NTMs).

The ITER ECH & CD Upper Launcher: Steps towards final design of the first confinement system

The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) Upper Launcher, whose preliminary design was approved in 2009, is on its way towards the final design. The design work is being done by a consortium of several European research institutes in tight collaboration with F4E. The main focus is the finalization of the design of all components for the First Confinement System (FCS), which forms the vacuum and Tritium barrier. The FCS comprises structural components as well as the external waveguide components in the port cell. Structural components of the FCS include the flange seal, backend frame and closure plate. The external waveguide components include the isolation valve, CVD diamond windows, miter bends and straight waveguides. Because finalizing of the design of these components is directly influenced by the layout of many in-vessel components, the design work includes also further development of the entire launcher. This paper summarizes the most recent status of the design work on the structural components of the launcher FCS, which are the support flange, the socket, the closure plate and feed-throughs for waveguides and cooling pipes. The design work includes the engineering layout of these components in accordance with system requirements, load specifications and Quality and Safety classification. An outline of the overall design of the launcher will be presented. The design progress was based on a set of related analyses, of which particular results are given. Also the integration of the associated mm-wave components, assembly strategies, neutronic aspects and the design of the shielding components will be described.

Review of the Innovative H&CD Designs and the Impact of Their Configurations on the Performance of the EU DEMO Fusion Power Plant Reactor

Heating and current drive (H&CD) systems are being investigated for a demonstration fusion power plant DEMO to deliver net electricity for the grid around 2050. Compared to ITER, which has to show the generation of 500-MW thermal power, the target of DEMO is the successful production of 300 to 500 MW electrical power to the grid and to aim for a self-sufficient tritium fuel cycle. Three H&CD systems are under development for DEMO in Europe, the electron cyclotron (EC) system, the neutral beam injection (NBI) system, and the ion cyclotron system. Based on present studies for plasma ramp-up, ramp-down, and flat top phases, to be further validated in more detailed simulations, the assumed total launched power needed from the H&CD system in DEMO is in the range of 50–100 MW, to be provided for plasma heating and control. This paper describes the design and Research and Development status of selected H&CD systems, considered for their deployment in the EU DEMO. It was always considered that different H&CD configurations and design variants will have an impact on the performances for the whole fusion plant. It shall be noted that the basis for the H&CD integrated design and system development is the actual version of the European fusion electricity roadmap. The project also elaborates on H&CD efficiency improvements which will reduce the recirculating power fraction in the future fusion power plants. Different studies under investigation will be discussed such as for NBI the photoneutralization and for EC novel concepts for gyrotron multistage-depressed collector.

From W7-X towards ITER and beyond: Status and progress in EU fusion gyrotron developments

In Europe, significant progress in gyrotron research, development and manufacturing has been made in 2014, starting from the successful continuation of the 1 MW, 140 GHz gyrotron production for the stellarator Wendelstein 7-X (W7-X) at Greifswald, Germany and the accelerated development of the EU 1 MW, 170 GHz conventional cavity gyrotron for the ITER tokamak at Cadarache, France. Based on that, a physical design activity was started which shall lead to a dual frequency gyrotron for TCV, Lausanne, Switzerland. Within the European fusion development consortium (EUROfusion), advanced gyrotron research and development has started towards a future gyrotron design which shall fulfil the needs of DEMO, the nuclear fusion demonstration power plant that will follow ITER. Within that research and development, the development of advanced design tools, components, and proper test environment is progressing as well. A comprehensive view over the status and prospects of the different development lines shall be presented.

The ITER EC H&CD upper launcher: Methodology in the FEM analyses of the diamond window unit subject to seismic and baking loads

The ITER electron cyclotron upper launcher (EC UL) is used to direct high power microwave beams generated by the gyrotrons into the plasma for magneto-hydrodynamic (MHD) control and heating and current drive (H&CD) applications. The UL consists of an assembly of ex-vessel waveguides (WGs) and an in-vessel port plug. The diamond window units form vacuum and tritium confinement boundaries between the torus volume and the transmission lines (TLs) which guide beams between 1 and 2 MW from the gyrotrons to the launcher.

Aufbau eines Versuchsstandes für den ECH Upper Launcher in ITER - Schlussbericht zum Vorhaben 3FUS0010 (KIT Scientific Reports ; 7694)

Um Plasmainstabilitaten zu begegnen, werden in vier der oberen Ports im ITER Vakuumgefas Electron Cyclotron Launcher installiert. Diese bestehen im Wesentlichen aus einer trapezformigen Stahlkonstruktion, welche die Mikrowellenkomponenten (im Wesentlichen Spiegel und Wellenleiter) beherbergt. Bei der Konstruktion eines solchen Launchers mussen als wesentliche Vorgaben die mechanische Festigkeit, die ausreichende Kuhlung des Systems und wirksame Abschirmung gegen Neutronen berucksichtigt werden.

Structural design and analysis of an ECRH launcher for JET

The future JET (Joint European Torus) program will be mainly focused on the consolidation of the physics basis of the main ITER scenarios. This gives a strong motivation for examining the feasibility of the construction and implementation of an ECRH (Electron Cyclotron Resonance Heating) system in JET for an intensive exploitation before the start of ITER. To advance this feasibility study towards the approval of the project, collaboration between the E4J (ECRH for JET) project team and the KIT (Karlsruhe Institute of Technology) design team of the ITER ECH Port Plug was decided. The aim of this collaboration was to raise the principal design requirements and to establish a rough design of the main components of an E4J system.