Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak

0566724 - ÚFP 2023 RIV GB eng J - Journal Article
Bogár, Klára - Varju, Jozef - Havlíček, Josef - Stöckel, Jan - Podolník, Aleš - Hron, Martin - Pánek, Radomír
Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak.
Plasma Physics and Controlled Fusion. Roč. 65, č. 2 (2023), č. článku 025004. ISSN 0741-3335. E-ISSN 1361-6587
R&D Projects: GA MŠMT(CZ) LM2018117; GA MŠMT(CZ) EF16_019/0000768
Institutional support: RVO:61389021
Keywords : neutral beam injection * auxilliary heating * COMPASS tokamak * power balance * beam duct scraping
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/aca629

Two identical neutral beam injectors (NBIs) have been installed on the COMPASS tokamak. Each of them is capable of producing a deuterium (or hydrogen, helium) neutral beam with nominal power of up to 400 kW at 40 keV. Since the COMPASS tokamak is a compact machine, the design of the neutral beams was carefully optimized to fit the neutral beam through the narrow ports of the tokamak. However, once the neutral beams are operated out of the scope of their optimal parameters, additional power losses occur due to neutral beam scraping. This article investigates the amount of power loss due to neutral beam scraping. The losses are calculated using the neutral beam models and measured neutral beam parameters. The calculated results are compared with the measured power delivered into the plasma. Two different neutral beam models are employed. One describes the neutral beam as a sum of small beamlets, which are Gaussian-like. The second one describes the neutral beam as a single Gaussian beam. The amount of the power lost to scraping is determined by both models and compared. Neutral beam parameters, the input parameters for both models, are derived from the Doppler-shifted spectra emitted by fast neutral atoms. It is shown that when operating NBIs at nominal parameters, the scraping losses are negligible ( <
Permanent Link: https://hdl.handle.net/11104/0341372