NNBI system based on ITER HNB for beam-target DD neutron generation in an optimized stellarator

A classical 1D slowing down model is applied to beam-injected deuterons in a deuterium plasma (DD), including the effect of shine-through, thermal beta limits, and beam beta limits. The model reveals that an economically useful rate of neutrons can be produced by negative-ion-based neutral beam (NNBI) at a near-optimal energy of 1 MeV into an optimized quasisymmetric stellarator with major radius around 2 meters. Parametric dependence of the neutron rate is discussed. This NNBI system is coincidentally at the same energy of the ITER Heating Neutral Beams (HNBs), allowing significant technology re-use. We propose a system which is a trivial scaling from the ITER HNBs, using 2 ion sources instead of 8 and 1-segment grids instead of 4. The length of the NNBI system can not be reduced by much, but areas of improvement are discussed.