Heating & Current Drive Efficiencies, TBR and RAMI considerations for DEMO

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 produced in the balance of plant (BoP) the H&CD efficiency optimization is one of the main goals of the DEMO development. The energy consumption of the H&CD sub-systems in different plant modes & states and plasma phases need to be strongly considered for the DEMO conceptual design. The H&CD power for DEMO, based on physics scenarios for the plasma phases, is needed for plasma breakdown, plasma initiation, heating to H-mode, burn control, controlled current ramp-up and -down, MHD control and other functions. Plasma control will need significant installed HCD power, though not continuously used. Previously, in the DEMO baseline definition, 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, hence to move closer to a mature design, it is proposed to use more realistic state-of-the-art efficiencies. These will continuously be updated based on new findings. Those designs must have achieved a minimum Technical Readiness Level (TRL) either by evidence and validation in the laboratory or preferably by being tested in a relevant environment. This presentation discusses the transition from previous to present assumptions and the impact on the DEMO power plant and basic tokamak configuration. A comparison of the various HCD 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 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.