Optics and Thermomechanical Analysis of the Accelerator for the DEMO Neutral Beam Injector

The injection of high energy neutral beams is one of the main tools to heat the DEMO plasma up to fusion conditions. A conceptual design of the neutral beam injector (NBI) for the DEMO fusion reactor is currently being developed by Consorzio RFX in collaboration with other European research institutes. High injector efficiency and RAMI, which are fundamental requirements for the success of DEMO, have been taken into special consideration for the DEMO NBI. A novel design of the beam source for the DEMO NBI is being developed featuring multiple subsources, following a modular design concept, capable of increasing the reliability and availability of the DEMO NBI. A full comprehensive model of the extraction/acceleration system has been developed, able to estimate all the main physics and engineering aspects (beam optics, coextracted and stripped electrons, heating power deposited on the grids, working temperature of the grids, and related stress and deformations) in a self-consistent way. This paper describes the results obtained applying the full comprehensive model to the present design of the extraction/acceleration system.