The ITER divertor vertical target has to sustain heat fluxes up to 20 MW m−2. The concept developed for this plasma facing component working at steady state is based on carbon fibre composite armour for the lower straight part and tungsten for the curved upper part. The main challenges involved in the use of such components include the removal of the high heat fluxes deposited and mechanically and thermally joining the armour to the metallic heat sink, despite the mismatch in the thermal expansions. Two solutions based on the use of a CuCrZr hardened copper alloy and an active metal casting (AMC®) process were investigated during the ITER EDA phase: the first one called ‘flat tile geometry’ was mainly developed for the Tore Supra pumped limiter, the second one called ‘monoblock geometry’ was developed by the EU Participating Team for the ITER project. This paper presents a review of these two solutions and analyses their assets and drawbacks: pressure drop, critical heat flux, surface temperature and expected behaviour during operation, risks during the manufacture, control of the armour defects during the manufacture and at the reception, and the possibility of repairing defective tiles.

Experiments performed with the Tore Supra vented pump limiter (Vented-PL) demonstrate that a vented structure exhibits a significant particle exhaust capability while allowing moderate heat flux density on the whole head surface. An experimental comparison is presented between a classical pump limiter with throats (Throat-PL) and the test Vented-PL for both deuterium and helium ohmic discharges. It is shown that, without active pumping, the deuterium and helium pressures in the Vented-PL plenum are typically 3 times lower than those measured in the Throat-PL plenum. However, when pumping is activated, this pressure is demonstrated to be high enough to allow the Vented-PL to control actively the plasma density. With only one modular Vented-PL, an exhaust efficiency (defined as the global recycling coefficient reduction) as high as 6% has already been measured for a deuterium plasma

No abstract

No abstract