High heat flux components

The principle high heat-flux components for the new pumped divertor are the neutraliser or target plates. The outside plates are positioned in such a way as to enhance the flux of hydrogenic neutrals, generated at these plates, into the adjacent cryopump. One of the key concepts behind the divertor design is the radiation of a substantial portion of the plasma power by the plasma in the divertor channels thus reducing the load on the target plates. The radiation will be effected by the impurities sputtered from the target plates and possibly by material injected near the target plates. In order to maintain compatibility with the other plasma facing components and to ensure that the main plasma is not jeopardised, the target plates will be covered with a layer of beryllium. The target plates are being designed with the capability to dissipate a large fraction of the 40 MW of input power under stationary conditions. A system of water cooled components based on the extensive in-house experience with such components gained with the JET neutral beam injection systems is being designed. The average power flux density onto the target plates will be reduced by a sweep of the separatrix over the plates by 6-8 cm. (author)