Numerical modelling for beam duct heat loads calculations and application to the new 1 MW neutral beam injector in the COMPASS tokamak

0565919 - ÚFP 2023 RIV GB eng J - Journal Article
Jaulmes, Fabien - Zadvitskiy, Georgiy - Bogár, Klára - Mysiura, Illia - Varju, Jozef - Jeřáb, Martin - Komm, Michael - Imríšek, Martin
Numerical modelling for beam duct heat loads calculations and application to the new 1 MW neutral beam injector in the COMPASS tokamak.
Plasma Physics and Controlled Fusion. Roč. 64, č. 12 (2022), č. článku 125001. ISSN 0741-3335. E-ISSN 1361-6587
R&D Projects: GA MŠMT(CZ) EF16_019/0000768; GA MŠMT(CZ) LM2018117
Institutional support: RVO:61389021
Keywords : beam * duct * fast ion * heat load * nbi
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 2.2, year: 2022
Method of publishing: Limited access
https://iopscience.iop.org/article/10.1088/1361-6587/ac985e

We introduce detailed numerical modelling of the fast neutral particles inside the duct of a new neutral beam injector (NBI) recently installed at the COMPASS tokamak (major radius R 0 = 0.56 m , vessel midplane minor radius a = 0.23 m , toroidal field B t = 0.9-2.1 T ). This new NBI system is able to deliver 1 M W power to the plasma at nominal injection energy of 80 k e V . Collisions with the background neutrals inside the beam duct give birth to fast ions according to the density of the gas and tabulated cross-sections. The ion trajectories are then computed in the complete 3D magnetic field, showing the importance of the stray magnetic field and the magnitude of the field within the gap in between toroidal coils.During the experimental campaign dedicated to the new 1 MW NBI, the beam duct heating was measured by a row of thermocouples located on the top-half of the beam duct. The fast ions collisions with the duct wall cause a local temperature increase with a characteristic pattern. In COMPASS, the location of the fast ions power deposition measured experimentally is in qualitative agreement with modelling of ion losses when following them after the re-ionization process. We trace back the details of the orbits corresponding to deposition at the hot-spot inside the beam duct. Quantitative comparison between the experiment and the simulation shows that a larger than expected amount of neutral gas was inside the duct and this study will guide the design of the future NBI duct in COMPASS Upgrade.
Permanent Link: https://hdl.handle.net/11104/0337393