Page 295 - Fundamentals of Magnetic Thermonuclear Reactor Design

274 Fundamentals of Magnetic Thermonuclear Reactor Design

FIGURE 8.4 Arrangement of ITER correction coils. (Copyright ITER Organisation, 2017).

particularly important for tokamaks, in which equilibrium is provided by the
feedback control of plasma displacements. Relevant methods rely on the mea-
surement of poloidal magnetic fields outside the plasma using electromagnetic
sensors.
The development of diagnostic systems based on magnetic measurements
involves a number of fundamental issues that have to be addressed. First, the
sensors must be adapted to the design and operation environment. Second,
algorithms must be developed for the reconstruction of the spatial position and
shape of a magnetic flux surface regarded as a plasma boundary. The precision
and speed requirements for such algorithms depend on their application (infor-
mation systems, closed-loop control systems, etc.) and on plasma itself, that is,
on the time of the plasma parameter changes.
In ITER and tokamak-based neutron sources, the installation of sensors
nearby plasma is a much more difficult task than in experimental tokamaks.
The sensors are exposed, among other things, to an intense neutron radiation.
This places additional constraints on the sensors number, position and design,
and requires radiation effects to be taken into account. Also, plasma reconstruc-
tion algorithms must be verified as fitting for reactor-relevant conditions. In