Conceptual design of NBI beamline for VEST plasma heating

摘要

A 10 m s-pulsed NBI (Neutral Beam Injection) system for VEST (Versatile Experiment Spherical Torus) plasma heating is designed to provide a beam power of more than 0.6 MW with 20 keV H degrees neutrals. The VEST NBI injector is composed of 2 sets of 20 keV/25A magnetic cusp type bucket ion source, neutralizer ducts, residual ion dump, NB vessel with a cryopump, and rotating calorimeter. The position and size of these beamline components are roughly determined with geometric calculation of beam power transmission: the overall length of beamline is 1.8 m, spacing between ground grid and neutralizer of 1.0 m, and position of residual ion dump is 0.8 m downstream from the neutralizer exit. Optimizing the gas feed between ion source and neutralizer can leads to a neutralization efficiency of similar to 76%. Finally, the beam power of maximum 0.6 MW can be delivered to the VEST plasma with a beam loss of 10%. (C) 2016 Elsevier B.V. All rights reserved.