An alternative ECRH front steering launcher for the ITER upper port

Presently, a remote steering (RS) antenna [C.P. Moeller, A method of remotely steering a microwave beam launched from a highly overmoded corrugated waveguide, in: Proceedings of the 23rd International Conference on IRMMW, Colchester, UK, 1998] is envisioned for launching the electron cyclotron current drive (ECCD) from the ITER upper port. The RS launcher has a strong engineering advantage in that the steering mechanism is placed outside of the ITER blanket, however, at the cost of reduced performance. In particular, the launcher has a limited steering range and a wide deposition width that results in submarginal performance for neoclassical tearing mode (NTM) stabilization. An alternative front steering (FS) launcher is proposed [M.A. Henderson, R. Chavan, F Sanchez, Front Steering ECCD Launcher Study for the ITER upper port, CRPP LRP 791/04], which has a wider steering range and a narrower deposition width offering above marginal performance for all plasma equilibria investigated. A two-mirror system (one focusing and one flat steerable) is used to project the RF beam waist far into the plasma. The steering mechanism avoids frictional surfaces that risk to block during operation and uses a gaseous He pneumatic system as a control actuator. D 2005 Published by Elsevier B.V.

Plasma production and transport in a simple magnetised toroidal plasma

Mario Podesta

This Thesis addresses questions related to transport phenomena and the plasma production mechanisms by injection of microwaves in the electron-cyclotron frequency range in the simple magnetised toroidal plasma TORPEX. The second subject is investigated in detail in Part II. The mechanisms of the interaction between the injected microwaves and the plasma are identified. The experimental results highlight the different roles played by the electron-cyclotron and upper-hybrid plasma resonances in the absoprtion of the microwave power by the plasma. The effects of the plasma-wave interaction on the electron distribution function are investigated, confirming that the high-energy electrons that are able to ionise the neutral gas mainly come from interactions at the upper-hybrid resonance. Based on the experimental results, an expression is derived for the particle source term, which can be used in numerical codes simulating the plasma dynamics on TORPEX. The plasma production mechanisms are then related to the properties of the time-averaged plasma profiles. A set of control parameters, including the injected microwave power and the vertical magnetic field, are identified. These allow one to vary in a systematic way the plasma profiles, as needed for a detailed study of plasma instabilities and related transport. The study of particle and heat transport is undertaken in Part III. A number of experimental and analysis techniques, including a method based on the combination of "conditional-average sampling" and "boxcar-averaging", are applied to identify and quantify specific contributions to the total fluxes. The two-dimensional temporal behaviour of density, electron temperature and plasma potential is simultaneously reconstructed, thus contributing significantly to the characterisation of transport mechanisms at play in TORPEX plasmas. Two clearly distinct mechanisms are mainly responsible for the transport across the magnetic field. They are respectively associated to unstable low-frequency electrostatic modes, identified as drift waves and interchange modes, and to intermittent high-density plasma structures (or blobs). It is shown that the blobs originate from the intermittent radial expansion of the unstable modes in a region of strongly sheared E × B flow.

EPFL2007

Overview of the ITER EC H&CD system and its capabilities

Stefano Alberti, Robert Bertizzolo, René Chavan, Timothy Goodman, Jean-Philippe Hogge, Jean-Daniel Landis, Ioannis Pagonakis, Emanuele Poli, Laurie Porte, Francisco Sanchez, Olivier Sauter, Minh Quang Tran, Hartmut Zohm

The Electron Cyclotron (EC) system for the ITER tokamak is designed to inject >= 20 MW RF power into the plasma for Heating and Current Drive (H&CD) applications. The EC system consists of up to 26 gyrotrons (between 1 and 2 MW each), the associated power supplies, 24 transmission lines and 5 launchers. The EC system has a diverse range of applications including central heating and current drive, current profile tailoring and control of plasma magneto-hydrodynamic (MUD) instabilities such as the sawtooth and neoclassical tearing modes (NTMs). This diverse range of applications requires the launchers to be capable of depositing the EC power across nearly the entire plasma cross section. This is achieved by two types of antennas: an equatorial port launcher (capable of injecting up to 20 MW from the plasma axis to mid-radius) and four upper port launchers providing access from inside of mid radius to near the plasma edge. The equatorial launcher design is optimized for central heating, current drive and profile tailoring, while the upper launcher should provide a very focused and peaked current density profile to control the plasma instabilities.

Elsevier2011

Status Status of the final design of the EC UPP launcher

René Chavan, Jean-Daniel Landis

Four EC H&CD (Electron Cyclotron Heating and Current Drive) launchers will be installed into the upper ports #12, #13, #15 and #16 in ITER. Beside plasma heating their main purpose is to counteract plasma instabilities by injecting up to 20 MW of microwave power at a frequency of 170 GHz at dedicated positions into the plasma. The microwave power is generated in 24 Gyrotrons outside the Tokamak and transmitted into the dedicated ports by 8 waveguide lines per launcher. After passing a CVD (Chemical Vapor Deposition) diamond window and another section of circular waveguides, the microwaves are quasi-optically guided into the plasma by an adjusted set of mirrors. These mirrors and also the foremost segments of the waveguides are mounted into the Upper Port Plug, which is a massive steel structure capable to dissipate up to 800 kW heat and to withstand heavy mechanical loads induced mainly from plasma disruptions. This paper presents the most recent status of the design of the EC H&CD Upper Port Plug (UPP), featuring the construction of the supporting structure and the BSM (Blanket Shield Module) with its plasma facing First Wall, the PHTS (Primary Heat Transfer System) water cooling layout, the shielding components engineering, the microwave system integration and comprehensive manufacturing strategies. Also correlated computational analyses to prove the final design of the launchers structural system are given.

ELSEVIER SCIENCE SA2018

Plasma production and transport in a simple magnetised toroidal plasma

Mario Podesta

EPFL2007