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International audience; Within the European development of a future tokamak demonstration fusion power plant (DEMO) [1] the pre-conceptual studies on the plasma diagnostic and control (D&C) system are progressing to prepare the basis for reliable plasma operation at high overall performance [2]. A variety of plasma diagnostics will be employed on DEMO together with advanced control techniques in order to provide an accurate knowledge of the plasma state, which is needed to maintain plasma operation within the allowed physical and technical limits. The integration of diagnostic front-end components has to cope with strong adverse effects arising from neutron and gamma irradiation, heat loads, impinging particles and forces. In this environment, the quality of measurements can only be ensured for longer periods by using robust diagnostic components, mounting them in sufficiently protected (retracted) locations, and any maintenance can only be performed via remote handling. Major open issues are the durability of magnetic measurements in the presence of irradiation induced effects and the feasibility of detachment control under DEMO conditions. In parallel to diagnostic developments, the details of the main control issues are being formulated and investigated by quantitative plasma control simulations. To obtain the envisaged performance DEMO operates close to some physics limits where even small disturbances, if not properly controlled, can trigger major variations of the plasma parameters. Equilibrium control requires high control power and can drive the poloidal field coil system to its operational limits. Within this paper, we will provide an overview on the current status of the ongoing D&C developments for the European DEMO concept.

The integration of heating current drive (HCD) systems in the EU DEMO tokamak must address a number of issues, namely space constraints in the tokamak building, remote handling requirements, breeding blanket penetration, neutron and photon radiation shielding, compliance of penetrations of the primary vacuum with safety and vacuum criteria, and a large number of loading conditions, in particular heat, electromagnetic (EM), and pressure loads in normal and off-normal conditions. A number of pre-conceptual design options of the vacuum vessel (VV) port and the port-plug are under assessment and need to be verified against all requirements and related criteria. The identification of the functional (or physics) requirements of the HCD systems remains an ongoing process during the pre-conceptual design phase, hence some initial assumptions had to be made as a basis for development of the design of the vacuum vessel ports and the HCD port plugs. The paper will provide an overview of present margins in the functional/physics requirements and the rationale behind the assumptions made in order to allow development of the pre-conceptual design options. Furthermore it will introduce the initial design concepts of the Electron Cyclotron (EC) Launchers and the Neutral Beam (NB) Injectors integrated in the equatorial ports. The NB duct design in DEMO and related issues such as transmission and re-ionization losses will be also addressed. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the EURATOM research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

The neoclassical tearing mode (short NTM) is an instability which, under appropriate conditions, develops in tokamak plasmas, leading to an undesirable degradation of the confinement capability of the machine. In the present work, the stability of this mode is addressed, with emphasis on the effects connected to the interplay between the mode rotation and the characteristic timescales of the particle motion. These effects are found to considerably affect the stability of the mode. Furthermore, the first results concerning a more complete (gyrokinetic) modelling of the NTM dynamics are presented. Die Neoklassische Tearing Mode ist eine Instabilität, die sich unter bestimmten Bedingungen in Tokamak-Plasmen ausbildet und zu einer unerwünschten Verminderung des magnetischen Einschlusses in Experimenten führt. In der vorliegenden Arbeit wird auf die Stabilität dieser Mode mit besonderem Augenmerk auf Effekte, die sich mit der Wechselwirkung zwischen der Rotation der Mode und den charakteristischen Zeitskalen der Teilchenbewegung beschäftigen, eingegangen. Es stellt sich heraus, dass dieses Zusammenspiel die Stabilität der Mode wesentlich beeinflusst. Des Weiteren werden erste Ergebnisse, die die Beschreibung der Dynamik von NTMs auf einem fundamentaleren (gyro-kinetischen) Erklärungsmodell beinhalten, präsentiert.