Abstract
NET is conceived as an experimental reactor with the aim of demonstrating reactor-relevant plasma performance and reliable operation of the device as well as developing and testing components for a demonstration reactor. For power and particle exhaust both a single-null and a double-null poloidal divertor configuration are under consideration. An intense modelling effort is undertaken to predict the heat load and erosion characteristics for these configurations. Under burn conditions, the divertor will operate in the high-recycling regime. The resulting heat loads on the divertor plates are predicted to be somewhat more demanding in the case of a single-null divertor. If one excludes working under conditions where a large part of the power is exhausted by radiation from the plasma edge, refractory metals (W, Mo) have to be used for the plasma-facing surface of the divertor plates, the radial heat and particle transport in the scrape-off layer must be large ( X e ⊥, ≈ 4 m 2/s; D ⊥ ≈ 1 m 2/s) and the plasma density at the edge of the discharge must be high ( n s ≈ 5 × 10 19 m −3). Erosion of a bare stainless steel first wall, under normal working conditions, appears to be within acceptable limits, but the use of graphite armouring is considered in order to avoid wall damage due to localized loads of highly energetic particles and to protect against disruptions. Such a solution would also be consistent with the anticipated requirements during start-up. For both the first wall and the divertor plates various concepts are under consideration. Using replaceable tiles as plasma-facing components throughout appears attractive.
Published Version
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