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The influence of neon and nitrogen seeding on the divertor heat load in JET tokamak is studied in terms of the numerical simulations of the whole device by the self-consistent core–edge code COREDIV and results are presented for advanced tokamak scenarios. First, the code has been applied to simulate two JET shots (#69980, #69987) characterized by different radiation levels. With this basis the code is used next to provide guidance for the JET experiments in terms of: effects on the heat load at the target plates for various x-point positions with respect to the target plates, and the effect of higher plasma and separatrix density, as well as effects of pure or mixed Ne/ N 2 -seeding.

A numerical investigation of plasma parameters in a diverter configuration of COMPASS tokamak is presented. The plasma parameters in the device are analyzed in the frame of the self-consistent description of the central plasma and edge region. The possibility of achieving high recycling and detached regimes in the boundary layer of the COMPASS tokamak is discussed.

In this paper, we discuss the phenomena that link particle recycling from the vessel walls in the L-mode during discharge start-up and the core confinement in the H-mode during the subsequent main heating phase. We consider available data of JET experiments that aimed at approaching fully non-inductive ITER-relevant steady-state conditions and show that the high electron temperature produced at the edge by a low recycling during start-up tends to favour the build-up of high normalized β(βN) regimes in the H-mode, the confinement being improved in a large plasma volume. To provide an insight into this complex phenomenon we have modelled the relation between particle recycling in the scrape-off layer and the evolution of plasma transport, plasma current density and shear as well as the stability properties for such experimental conditions. The results confirm the existence of a link between the confinement in the H-mode phase and the values at the edge of electron temperature, bootstrap current density and local magnetic shear during start-up. Such a link could favour these regimes to be self-sustained in time. © 2013 IOP Publishing Ltd.

A simple analytical model is presented that describes impurity ion production and transport in the tokamak scrap-off layer (SOL). The equations of the model are solved analytically in the test particle approximation. The solution, as a function of different plasma parameters and target materials, is discussed in the case in which the background plasma is described by the simple SOL model and a comparison between the model and the numerical results of a 2-D multifluid code is presented

The hydrogen plasma and impurity flows parallel to the magnetic field lines in a collissional tokamak scrape-off layer are numerically investigated. The physical model is developed on the basis of electron-ion fluid equations for hydrogen plasma and rate equations for impurities. A complex model valid for arbitrary concentration of impurity ions based on 21-moment Grad approximation is used to describe transport coefficients and thermal forces. Plasma interactions with neutral particles recycling at the divertor plate are taken into account. Steady state spatial profiles of the plasma and impurity (0, C) parameters are computed using the time relaxation method Possibility of helium exhaust is investigated.

A simple analytical model is presented for the plasma in the region outside the limiter which describes the impurity ions transport and production in the tokamak scrape‐off layer. The equations of the model are solved analytically in the test particle approximation for the simple SOL configurations. A discussion of the solutions for different plasma parameters and target materials is presented. Copyright © 1994 WILEY‐VCH Verlag GmbH & Co. KGaA