Numerical Analysis of NBI Heating in Thailand Tokamak-1 using NUBEAM Code

This study focuses on optimizing the geometry of the Neutral Beam Injection (NBI) system in Thailand Tokamak-1 (TT-1) using the NUBEAM neutral beam simulation code. When TT-1 operates with low-density hydrogen plasma during without auxiliary heating, the predicted plasma using the BALDUR code reveal a central electron density of 1.1 × 1019 m−3, with central electron and ion temperatures of 1.2 keV and 0.04 keV, respectively. Assuming a 20 keV, 1 MW hydrogen beam injected into the horizontal port of Section C on the mid-plane, we observed that for tangential radii (Rtan) less than 0.35 m, over 80% of the beam particles pass through the plasma without ionization, resulting in limited heating power absorption. Conversely, for Rtan values of 0.55 or 0.65 m, over 80% of the particles are deposited onto the background plasma, with absorption power by electrons and ions nearing 50% of total injected power. However, charge-exchange power loss also rises to 30%. The total driven current for Rtan = 0.55 and 0.65 m approaches 100 kA, comparable to the plasma current. Furthermore, some particles deposited on the low-field side experience prompt loss, striking the upper part of the vacuum vessel. Future work should conduct a comprehensive analysis of the impact of varying plasma parameters and beam characteristics on heating efficiency, as well as the investigation of instabilities driven by fast ions.