The ITER Divertor
 The divertor is one of the key components of the ITER machine. Situated along the bottom of the vacuum vessel, its function is to extract heat and helium ash — both products of the fusion reaction — and other impurities from the plasma, in effect acting like a giant exhaust system. It will comprise two main parts: a supporting structure made primarily from stainless steel, and the plasma-facing components, weighing about 700 tons. The plasma-facing components will be made of tungsten, a high-refractory material. |
 The three plasma-facing components of the ITER divertor: the inner and the outer vertical targets, and the dome. Located at the very bottom of the vacuum vessel, the ITER divertor is made up of 54 remotely-removable cassettes, each holding three plasma-facing components, or targets. These are the inner and the outer vertical targets, and the dome. The targets are situated at the intersection of magnetic field lines where the high-energy plasma particles strike the components. Their kinetic energy is transformed into heat; the heat flux received by these components is extremely intense and requires active water cooling. The choice of the surface material for the divertor is an important one. Only very few materials are able to withstand temperatures of up to 3,000°C for the projected 20-year lifetime of the ITER machine; these will be tested in ITER.
ITER planned to begin operations with a divertor target made of carbon fibre-reinforced carbon composite (CFC)—a material that presents the advantage of high thermal conductivity—to be followed by a second divertor with tungsten targets which offer the advantage of a lower rate of erosion and longer lifetime.
Currently, due to cost cutting considerations, the ITER management is investigating the feasibility of implementing tungsten right from the beginning of operations.
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