Abstract

The ion temperature in the plasma in a fusion reactor must be sufficiently high that the fusion reaction (probably between D<sup>+</sup> and T<sup>+</sup> ) will need to be high to ensure that the reaction rate is as high as is required. The plasma will be heated by the energetic alpha particle created in the fusion reaction, but it is widely accepted that additional (externally supplied) heating will also be required to ensure a sustained "burn" and, perhaps, to control the reaction rate. A reactor based on the tokamak confinement system requires a toroidal current to flow in the plasma. Most of that current will be created by the "bootstrap" effect, but an external method of driving current in the poloidal centre of the plasma is needed as the bootstrap current will be low, or zero in that region. Neutral beam injection is an efficient heating mechanism and it has the current drive efficiency required in a reactor. In this chapter the R&D required for an NBI system for a reactor, is considered against the background of the ITER NBI system design as the ITER beam energy and operating environment are reactor relevant. In addition the elements requiring most development are identified.

Keywords: neutral beam injection, negative ion sources, beamline design
