Term Definition
H&CD heating and current drive
H-alpha studies A diagnostic technique to study the plasma boundary by observing the alpha line (6563 A wavelength) of the hydrogen emission spectrum.
H-mode High mode, a regime of operation attained during auxiliary heating of divertor tokamak plasmas when the injected power is sufficiently high. A sudden improvement in particle confinement time leads to increased density and temperature, distinguishing this mode from the normal L-mode, "low mode" .
halo currents When the plasma column is displaced vertically a current is induced flowing from the plasma through the vacuum vessel (shortest way) and thence back into the plasma. It thus contributes to delaying the plasma vertical movement (Faraday’s law).
heat flux The total flow of heat in heat exchange
heat sink An element of a composite material or structure which acts as the main attractor of heat in the system. Thus in a cooled body the coolant is the ultimate heat sink, though often a solid material included for its good thermal conduction to the ultimate heat sink is often known as the heat sink and this is the role it plays among the solid elements.
heat sink lifetime The time the underlying substrate (the “heat sink”) of a plasma-facing component can be reliably predicted to fulfil its functional purpose (and therefore not need replacement).
heavy-ion beam probe A plasma diagnostic which probes the plasma with a beam of heavy ions.
helical twist A spiral twist of constant form and usually of constant radius. Thus the magnetic field lines in the tokamak have helical twists around the plasma, forming magnetic surfaces on which the twist pitch is constant.
helicity safety factor Also known as the plasma safety factor, this is aproximately the ratio
rBt/RBp (where r, R are minor , major radii of the torus, and Bp, Bt are poloidal and toroidal field strengths respectively). The safety factor is 2 x the number of times a field line circles the major axis of the plasma torus before going once round the minor axis of the plasma torus
HFS high field side
high-heat flux Power conducted or radiated from the plasma with loads exceeding 0.5 MW per square meter.
HT Home Team
HTS high temperature superconductor
HVAC heating, ventilation and air conditioning

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  Updated 13 February, 2017