Thermal Distribution Analysis of NBI Ion Sources Based on Experimental Study

Neutral beam injection (NBI) is a crucial auxiliary heating method in magnetic confinement fusion. However, the extreme thermal loads sustained by ion source components severely limit long-pulse operational stability, necessitating a thorough investigation into internal heat distributions. To address this challenge, experimental testing and data fitting are combined to quantify the thermal deposition characteristics of ion source across distinct operational phases. Empirical models are thus derived to map thermal distributions during filament heating, arc discharge, and beam extraction. The model reproduced the component-wise heat distribution measured during an 88-kV beam pulse. This framework provides a practical basis for thermal design, operating-parameter optimization, and heat-load management in long-pulse NBI systems.