A prototype of one of the plasma-facing components of the ITER tokamak - the first wall panel. (Credit © ITER Organization, www.iter.org)

Components of thermonuclear fusion research equipment that are in direct contact with the plasma or its peripheral regions. Most commonly, this is the divertor or the inner part of the chamber called the first wall. Extreme demands are placed on these components, as they must not only withstand high thermal stresses, but also not release impurities into the plasma, not absorb tritium, and endure strong neutron fluxes.