Search

The optics design of the multi-beamlet negative ion accelerator for MITICA has been verified by means of specific experiments in the NITS test facility at the QST lab, employing a scaled-down configuration having the same features as the accelerator of MITICA and ITER HNB. The experiments confirmed the validity of the accelerator design. However it was found that, in the presence of transverse magnetic field in the ion extraction stage, the ion beamlet deflection in numerical simulations was somehow underestimated with respect to the beamlet deflection inferred from thermal images of a CFC target exposed to the negative ion beam. A detailed benchmark, using also another (completely independent) numerical model of the accelerator, has allowed the identification of possible origins of the differences. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]