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나병근(Byungkeun NA) 한국진공학회 2020 진공 이야기 Vol.7 No.3
Neutral Beam Injector (NBI) is one of the main heating devices in atokamak. In this article, the structure and the characteristics of NBI are described in terms of vacuum and plasma. The current status of the domestic NBI technology is introduced through the performance of KSTAR NBI. A negative ion based NBI (NNBI) such as ITER NBI maintains high neutralization efficiency even at high beam energy. A NNBI is much more complicated than a positive ion based NBI, but it still has possibilities to increase its performance. The future of the NBI research and development is found in NNBI.
Characteristics of cylindrical plasma discharge with a thermal electron beam
Bae, Inshik,Na, Byungkeun,Chang, Hongyoung American Institute of Physics 2016 Physics of plasmas Vol.23 No.9
<P>Widely used plasma types, such as capacitively coupled plasmas and inductively coupled plasmas, have been studied by several researchers, and their uses have been thoroughly explored. In contrast, electron beam plasmas have not been well studied in wide pressure or voltage ranges. Therefore, it is necessary to investigate their general characteristics, such as electron densities and temperatures. In this study, we focus on the electron mean free path and investigate the general characteristics, such as the electron density, temperature, plasma potential, and breakdown voltage, of a cylindrical plasma discharge with a thermal electron beam. An electron density of about 10(8)-10(9) cm(-3) and an electron temperature of 1-2 eV were obtained experimentally. The dependence of these parameters on the pressure and anode voltage is also investigated. Published by AIP Publishing.</P>
Reinforcement of the Magnetic Lens Effect in the Dipole Magnet for a Neutral Beam Injector
Geonwoo Baek,Jinhyun Jeong,Min Park,Byungkeun Na,Seul Chan Hong,Jong-Gu Kwak 한국자기학회 2023 Journal of Magnetics Vol.28 No.3
Dipole magnet for a neutral beam injector is a magnetic device deflecting residual ions to an ion dump. For the high power neutral beam injection to fusion plasma, the heat load on the surface of the residual ion dump should be under acceptable level. We investigate the magnetic lens effect of the bending magnet for beam expansion cases. To intensify the magnetic lens effect, the height of the field clamp in the magnetic core is adjusted. The COMSOL Multiphysics software is employed to calculate a magnetic flux density for the dipole magnet, to trace an ion beam trajectory, and to evaluate a heat distribution on the beam dump. Simulation results reveal that the longitudinal magnetic field at the magnet entrance has a significant effect on the heat distribution in the ion dump surface, and hence the local heat flux is considerably alleviated by the field clamp with adjusting the height of the clamp.