Status of physics design of the HNB accelerator for ITER

Abstract. The physics design of the accelerator for the Heating Neutral Beamline (HNB) on ITER is still being worked on and this paper describes the design considerations, choices and status of the same. Equal acceleration gaps of 85 mm have been chosen to improve the voltage holding while keeping the beam divergence low. Kerbs and biaxial (and/or oblique) apertures are used to compensate for unwanted magnetic deflection, beamlet-beamlet interaction and to point the beamlets in the right direction. A combination of long-range and short-range magnetic fields is used to reduce electron leakage between the grids and limit the transmitted electron power to below 800 kW.