In-line magnetic residual ion dump for the ITER neutral beam system

An alternative magnetic residual ion removal concept with in-line ion dumps for the ITER neutral beam system is presented. The target plates are hit from one side and form a 500 mm wide opening to the beam. First calculations show that for the most severe case of a 3 mrad beam the maximum power load (in hot spots) can be kept below 17 MW/m2. Although the magnet creates additional stray fields and the concept is more complicated than the present design of an electrostatic ion removal system, the overall beamline transmission increases by about 10% (i.e. additional 1.7 MW injected power for each beamline) due to the open structure of the magnet and the ion dumps. Furthermore, the concept offers a much larger operating window regarding beam alignment, divergence and steering and it avoids creating accelerated secondary electrons.