Determination of the Operating Current of the Bending Magnet in the KSTAR Neutral Beam Injector
Byoung Seung Kim, Geonwoo Baek, Jae Young Jang, Jaewook Kim, SeulChan Hong, Jinhyun Jeong *
The Neutral Beam Injector (NBI) is a critical system for auxiliary plasma heating in magnetic confinement
fusion, delivering high-energy neutral particles that can penetrate the tokamak’s magnetic field. The KSTAR
NBI produces deuterium beams with energies up to 100 keV, resulting in substantial thermal loads on beamline
components. Accurate modeling of beam trajectories is essential for predicting beam losses and ensuring
structural integrity during long-pulse experiments. In this study, a beamlet-based trajectory model was
developed using realistic beamlet geometries and experimentally obtained input parameters, such as beam
fractions and divergence angles measured via Doppler shift spectroscopy. Model predictions were validated
through comparison with measured beam profiles at both the calorimeter and the ion dump. This work aims to
enhance the safety of the ion dump by evaluating the beam distribution characteristics and determining the
optimal operating current of the bending magnet. The results contribute to improving the structural reliability
of the NBI-2 during long-pulse operation.