Improved Conceptual Design of the Beamline for the DTT Neutral Beam Injector

The main purpose of the Divertor Tokamak Test facility (DTT) is to study alternative solutions to mitigate the issue of power exhaust under integrated physics and technical conditions relevant for ITER and DEMO. In this framework, the conceptual design of the beamline for the DTT Neutral Beam Heating system is here summarized, with a particular focus on the technical solutions adopted to fulfill the requirements and maximize beamline performances. The proposed system features a beamline providing deuterium neutrals (D0) with an energy of 510 keV and an injected power of 10 MW. Various design options were considered, and a comprehensive set of simulations was carried out using several physics and engineering codes to drive the choice of the most suitable design options and optimize them, aiming at finding a good compromise among different design requirements. These simulations mainly regard the efficiency of the main processes, the optics of the beam, the physics reactions along the beamline (stripping, charge-exchange and ionization), the thermo-mechanical behaviour of the acceleration grids and the coupling between the beam and the plasma in the tokamak chamber. This paper describes the design of the main components of the injector for the DTT NBI system, i.e. ion source, accelerator, beam line components and vacuum vessel, explaining the motivations for the main design choices.