LOW ACTIVATION MATERIALS(LAM)

Optimisation of the chemical composition of materials can significantly reduce their radio-activation following neutron bombardment in a fusion device. It is important to reduce long-term activation to facilitate the recycling or disposal of materials. Sometimes the terms RAM (reduced activation materials) and RAFM (reduced activation ferritic-martensitic) steels may be encountered.


















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HELIAS

A stellarator configuration in which the coils resemble distorted, non-planar toroidal field coils - no continuous helical coils or tokamak-like poloidal field coils are present. The Helias (HELIcal Advanced Stellarator) has been proposed as the most promising stellarator concept for a power plant, with a modular engineering design and optimised plasma, MHD and magnetic field properties. The WENDELSTEIN 7-X device (q.v.) is based on a five field-period Helias configuration.

CYLINDRICAL APPROXIMATION

An approximation to the true tokamak geometry in which the torus is cut and straightened, so that the toroidal direction becomes the cylinder axis. There are two directions of symmetry: along the axis (the ‘toroidal' direction) and about the axis (the ‘poloidal' direction).

COMPASS(-C)(-D)

Compact Assembly: the Culham conventional tokamak facility. COMPASS-C (with circular vacuum vessel) operated from 1989-91; COMPASS-D (with D-shaped vacuum vessel) operated until March 2001. COMPASS-D has a magnetic geometry similar to that of JET and therefore has played an important role in scaling experimental results through JET to ITER. It has been now been transferred to Prague, for experiments by the Czech Association.

E.C.C.D

Electron cyclotron current drive. Non-inductive current drive using ECRH.

DEUTERIUM

A stable isotope of hydrogen, whose nucleus contains one proton and one neutron. Deuterium plasmas are used routinely in present-day experiments; in a fusion power plant the plasma will consist of a mixture of deuterium and tritium which fuse more readily than two deuterium nuclei.

BREEDER

CENTRE POST

A current-carrying central rod placed down the symmetry axis of a spherical tokamak to produce the toroidal field. This is a crucial component determining the economics of fusion power from spherical tokamaks.

DBTT

As a material is cooled a temperature is reached at which it loses its ductile properties and becomes brittle. This ductile-to-brittle transition temperature (DBTT) is a key factor in the development of fusion structural materials because its value increases under irradiation. The development of steels that retain a DBTT below the lowest working temperature encountered during operational shutdowns is a major materials objective.















N. CORTEZ

VEGISVEIEN

A method of driving plasma current that does not depend on transformer action (e.g. by using RF waves or neutral beams); necessary for a continuously operated power plant, since transformer action is cyclic. Also applied to control instabilities and to optimise confinement.

LA CALIFORNIE

DENSITY FUNCTIONAL THEORY

Density functional theory is a successful approach for describing the ground state properties of metals, semiconductors, and insulators, for both standard bulk materials and more complex materials. The interacting system of electrons is described via its density and not via its many-body wave function. For N electrons in a solid this means that the basic variable of the system depends only on the three spatial coordinates, rather than 3N degrees of freedom.


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OHMIC HEATING

Heating in addition to Ohmic heating. Used to heat tokamaks to temperatures at which Ohmic heating is no longer efficient. Usually involves the use of neutral beams of high energy particles or radio-frequency waves.

DRIFT ORBITS

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LOS ANGELES

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