Gas and power flow in the ITER neutral beam injectors

By estimating gas and power flows, the feasibility of the present design for a 50 MW ITER-NBI system with three modules has been investigated. Through a careful study, gas flow rates supplied to the system were reduced. The gas flow rates per module are 1.5 Pa m³ /s from the ion source and 11.2 Pa m³/s from the neutralizer. The gas flow regenerated from one module over 1000 s is 22 g, which can be easily processed by the ITER tritium plant. The reduced gas flow rates result in lower beam losses due to collisions with D₂ molecules. The 40 MW D^- beam produced in the ion source/accelerator per module loses 2.8 MW in the neutralizer, 16.3 MW in the residual ion dump, and 1.2 MW in the duct. These powers can be easily removed by conventional cooling technology. Assuming an additional 15% loss due to beam halo with a poor beam divergence of 15 mrad, D⁰ beam power delivered to torus is 16.7 MW per module. This paper describes the calculation model, sensitivity analyses, and gas and power flows in the ITER-NBI module