AbstractA conceptual design of a 2 MeV neutral beam injection system for the Steady State Tokamak Reactor is described. The system nominally delivers a 2 MeV, 60 MW neutral deuterium beam to the reactor plasma through two tangential ports. On each port is mounted one beamline which has eight ion source/accelerator modules. The modules are arranged off the beamline axis and the accelerated ion beams are deflected by the ion beam bending system to be guided to the neutralizer cell. This arrangement prevents each module from being exposed to an intense direct irradiation from the reactor and makes it possible to use many ion source/accelerator modules per port. Since the ion beam output per module can be reduced, a Cockcroft-Walton type DC high voltage generator is adopted, so that high voltage transmission lines can be eliminated. Additionally, maintenance of the module is easy and simple, since all modules are arranged on the same floor.In this paper, a design of the ion beam bending system, which is a key issue to realize this advantageous arrangement, is described in detail, together with the overall description of the 2 MeV neutral beam injection system.
Present status of the negative ion based NBI system for long pulse operation on JT-60U