Fusion energy research aims to develop an economically and environmentally sustainable energy system. The tokamak, a doughnut shaped plasma confined by magnetic fields generated by currents flowing in external coils and the plasma, is a leading concept. Advanced Tokamak (AT) research in the DIII–D tokamak seeks to provide a scientific basis for steady-state high performance operation. This nece...

The penalization method is used to take account of obstacles, such as the limiter, in a tokamak. Because of the magnetic confinement of the plasma in a tokamak, the transport occurs essentially in the direction parallel to the magnetic field lines. We study a 1D nonlinear hyperbolic system as a simplified model of the plasma transport in the area close to the wall. A penalization which cuts the...

Particle transport in thermonuclear plasmas depends basically on the number of directions of symmetry in the plasma configuration. The search for toroidal confinement devices alternative to the tokamak has led to systems like the stellarator, heliac, etc., all with less symmetry and consequently enhanced diffusion, especially at low collisionality regimes. Even for the tokamak, asymmetry effect...

Introduction Control of plasma profiles is an essential ingredient in tokamak operation, in particular to access improved confinement regimes where the safety factor (q) profile plays a major role in determining plasma confinement and stability. This paper shows how physics models of profile transport can be used for improved plasma profile control methods. We show two distinct applications. In...

For the assessment of both tokamak and helical reactors, the base case reactor models are introduced, and parameter scan analyses on plasma beta, electric power output, maximum magnetic field strength and neutron wall loading are carried out. The assessment shows that high temperature operation is appropriate in tokamak reactors to increase bootstrap current fraction and current-drive (CD) effi...

Tokamak regimes with nearly zero or negative toroidal current in the central region (current hole) feature good plasma confinement properties and may be naturally attained in the advanced tokamak (AT) regime. On the other hand, quasi-steady-state AC plasma current operation in tokamaks relies upon the existence of current reversal equilibria with zero net toroidal current. In both cases a syste...

Recent gyrokinetic stability calculations have revealed that the spherical tokamak is susceptible to tearing parity instabilities with length scales of a few ion Larmor radii perpendicular to the magnetic field lines. Here we investigate this ‘micro-tearing’ mode in greater detail to uncover its key characteristics and compare it with existing theoretical models of the phenomenon. This has been...

Plasma-facing components (PFCs), consisting of plasma-facing materials (PFMs) and heat sink, are the first wall facing directly tokamak plasma, subjected to high heat flux (HHF) and bombardment of particles from the high temperature plasma. The exposure to the HHF and particles may damage the structural integrity of PFCs and shorten their service lives significantly if the connection of PFMs to...

Use of a large-area liquid lithium limiter in the CDX-U tokamak produced the largest relative increase (an enhancement factor of 5-10) in Ohmic tokamak confinement ever observed. Numerical simulations of CDX-U low recycling discharges have now been performed with the ASTRA code, utilizing a model with neoclassical ion transport and boundary conditions suitable to a nonrecycling wall, with fueli...

• Prof. James D. Callen, University of Wisconsin, Madison, WI, USA • Dr. Geoffrey Cordey, JET, Abingdon, UK • Dr. Otto Gruber, ASDEX U, Max Planck Institut, Garching bei Muenchen, Germany • Prof. Wendell Horton, IFS, University of Texas at Austin, TX, USA • Dr. Jean Jacquinot, Director of JET, Abingdon, UK (now Director of DRFC, C.E.A., Cadarache, France) • Prof. Guy Laval, Chairman, Ecole Poly...