Each neutral beam (NB) heating and current drive (H&CD) injector will deliver a deuterium beam of 16.5 MW (initial total 33 MW), with energy of 1 MeV, and will be able to operate for long pulses (up to 3,600 s). A system based on negative (D-) ions is chosen, due to their higher neutralisation efficiency than positive ions at this energy.
The size of the ion source and the required D- current density is not a large extrapolation (< x2) from the largest systems operational today.
In addition to heating and current drive, a small amount of plasma rotation is also provided by the NB injectors. For the H operation phase, the injectors can be operated in hydrogen, with beam energy ≤ 0.8 MeV and beam power ≤13 MW.The diagnostic neutral beam (DNB) has the same design features as the heating and current drive beams, but an energy of 100 keV. Injection is radial rather than tangential.
Production and acceleration of the neutral beams requires the sources to be located away from the plasma in a separate shielded cell. A shielded vacuum duct leads from there to the equatorial ports. The injector’s vessel is an extension of the primary vacuum boundary and is part of the primary barrier for contamination confinement. The common enclosure for all the injectors, the NB cell, which is part of the building, is part of the secondary confinement barrier.
More information can be found in the ITER Technical Basis 
.