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Term Definition
CAD computer aided design
CATIA Computer-graphics Aided Three-dimensional Interactive Application, CATIA is a three-dimensional CAD modeling software with all the appropriate interactive features to aid the designer in rapid production of self-consistent engineering models and drawings.
CB cold box
CD current drive
central electron density The plasma density on the toroidal axis in a tokamak.
central solenoid The tokamak component that produces and sustains the plasma current which heats and shapes the plasma.
CERN Centre Européen de Recherche Nucléaire (European Organization for Nuclear Research)
CfC, CFC Carbon fibre composite, a material made from carbon in which carbon fibres are placed, sometimes with preferred orientations, to give added strength.
charge-exchange A process in which there is a transfer of charge between two bodies during a collision between them (e.g. the collisional transfer of an electron from a neutral atom to a singly charged positive ion, the latter becoming neutral and the former charged).
CHF critical heat flux
collective instabilities Usually refers to Toroidal Alfven Eigenmode (TAE) instabilities and fishbone instabilities. TAEs can eject the alpha particles before they have slowed down and given their energy to the plasma, damaging the surrounding walls. Fishbone instabilities are caused by interaction between a major MHD instability and trapped particles, causing these trapped particles to be lost.
commissioning The process during which plant or reactor components and systems, after construction, are made operational and verified to be in accordance with design assumptions and to have met the performance criteria.
common-cause failure The failure of a number of devices or components to perform their functions as a result of a single specific event or cause.
compliant material Any material which has a flexible or flowing characteristic which enables it to maintain contact (and conductivity) between two surfaces which form a gap.
confinement Restriction of a hot plasma to a given volume as long as possible by magnets and pinch effects.
confinement enhancement factor The factor by which the plasma energy confinement time, calculated from a particular scaling law, would need to be enhanced in order to achieve a particular effect.
confinement time The amount of time the plasma is contained by magnetic fields before its energy leaks away.
controlled ignition A sustained equilibrium burn of a plasma with no auxiliary heating, other than for optimizing the plasma behavior. A state where energy release by thermonuclear reactions is sufficient to balance energy losses and is free of spontaneous excursions of thermonuclear power.
controlled thermonuclear fusion The process in which very light nuclei, heated to a high temperature in a confined region, undergo fusion reactions under controlled conditions, with the associated release of energy which may be harnessed for useful purposes.
cooldown Usually refers to the cooling period necessary to remove heat from a large superconducting magnet system to lower the temperature to the operating point.
“Cordey” pass The point in operating density and temperature which minimizes the auxiliary power needed to heat a plasma to controlled ignition.
core confinement Energy confinement related particularly to the plasma core (i.e the region within the separatrix).
correction coils Coils whose purpose is to compensate small errors in the confining magnetic field arising from fabricating misalignments.
CP contact person
critical heat flux (CHF), the heat flux at which there is a departure from nuclear boiling and steam bubbles coalesce to form an insulating layer which leads to very rapid heating and large loss of heat transfer.
cross section Measure the probability of interaction between an atomic nucleau, atom, or molecule and an incident particle, have the dimensions of area, and the appropriate unit for expressing them is the square meter.
cryogenic Term applied to very low-temperature substances and apparatus.
cryogenic technologies Technologies used to liquify helium and nitrogen (e.g. gas expansion) providing a low temperature coolant for magnets, vacuum pumping panels, etc., at around 4K and 80K respectively.
cryoplant The plant used to liquify helium and nitrogen to cool magnets, vacuum pumping panels, etc.
cryopump A vacuum pump system using panels cooled by liquid helium.
cryostat A vacuum vessel capable of being evacuated at room temperature built around a superconducting tokamak, which provides thermal insulation to maintain the magnets at low temperature.
CS See “central solenoid ”
CTB coil terminal box
CTE coefficient of thermal expansion, the fractional increase in length of a body per degree temperature rise
current drive A means for producing the toroidal plasma current.
current drive By pointing neutral particle beams roughly tangentially to the plasma major circumference, or by oscillating the microwave heating system antennae in a particular phase relationship with each other, toroidal plasma current can be driven non-inductively. These schemes can also enhance the ability of the plasma to drive its own toroidal current (the “bootstrap” effect). All these schemes weaken the need for inductively driven plasma current, and stretch the burn time, possibly to steady state.
CVD-W Chemical Vapour Deposition of tungsten onto a surface.
CW cold worked (i.e. material property); continuous wave (i.e. radiofrequency wave)
CX charge exchange, the method by which energetic particles in the scrape-off layer around the plasma core transfer energy to neutral particles in front of the divertor plate, thereby protecting the plates and spreading the heat loads.

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  Updated 13 February, 2017