Heating & current drive efficiencies, TBR and RAMI considerations for DEMO

Abstract

The heating & current drive (H&CD) systems in a DEMOnstration fusion power plant are one of the major energy consumers. Due to its high demand in electrical energy the H&CD efficiency optimization is an important goal in the DEMO development.The H&CD power for DEMO, based on physics scenarios for the different plasma phases, is needed for plasma initiation phases (incl. breakdown), current ramp-up, heating to H-mode, burn control, controlled current ramp-down, MHD control and other functions. Plasma control will need significant installed H&CD power, though not continuously used.Previously, in the DEMO1 2015 baseline definitions, optimistic forecasted H&CD efficiencies had been assumed in the corresponding system code (i.e. PROCESS) module. Realizing that there is a high uncertainty in the assumptions the efficiencies have been modified and the impact on the DEMO power plant and basic tokamak configuration are discussed in this article.A comparison of the various H&CD systems NBI (Neutral Beam Injection), Electron Cyclotron (EC), Ion Cyclotron (IC) in terms of impact on Tritium Breeding Ratio (TBR) due to various openings for the H&CD front end components in the breeding blanket (BB) is presented.For increasing the reliability as major features the power per system unit and the redundancy are identified leading to a new proposal for clusters for EC and modular ion-sources for NB.