Spectroscopic measurement of increases in hydrogen molecular rotational temperature with plasma-facing surface temperature and due to collisional-radiative processes in tokamaks

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2023-09
Major/Subject
Mcode
Degree programme
Language
en
Pages
16
1-16
Series
Nuclear Fusion, Volume 63, issue 9
Abstract
Spatially resolved rotational temperature of ground state hydrogen molecules desorbed from plasma-facing surface was measured in QUEST, LTX-β, and DIII-D tokamaks, and the increases of the rotational temperature with the surface temperature and due to collisional-radiative processes in the plasmas were evaluated. The increase due to collisional-radiative processes was calculated by solving rate equations considering electron and proton collisional excitation and deexcitation and spontaneous emission. The calculation results suggest a high sensitivity for the rotational temperature to electron and proton densities, but a negligible sensitivity to the electron, proton, and surface temperatures. In the three tokamaks with different plasma parameters and plasma-facing surface materials, the spatial profile of the rotational temperature was estimated using Fulcher-α emission lines (600-608 nm). In QUEST, the spatial profile of the rotational temperature was estimated from spatially resolved spectra. In the other tokamaks, the rotational temperature was evaluated assuming a single point emission with a location determined from the Fulcher-α emission profile as measured with a filtered camera. In metal-walled devices QUEST and LTX-β, the rotational temperature increased with the surface temperature, and the calculated collisional-radiative increase is consistent with measured increase assuming that the rotational temperature at the surface is approximately 500-600 K higher than the surface temperature. In DIII-D with carbon walls, a larger collisional-radiative increase than the other tokamaks was observed because of the higher density leading to a large difference from the calculated increase compared to the other smaller tokamaks. Measurement of the Fulcher-α emission profile with higher spatial resolution in DIII-D may reduce the difference and reveal the effect of the surface temperature on the rotational temperature. These results show the increases in the rotational temperature with the surface temperature and dueto the collisional-radiative processes.
Description
Publisher Copyright: © 2023 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd.
Keywords
DIII-D, emission spectroscopy, hydrogen molecule, LTX-β, plasma-surface interaction, QUEST, rotational temperature
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Citation
Yoneda , N , Shikama , T , Scotti , F , Hanada , K , Iguchi , H , Idei , H , Onchi , T , Ejiri , A , Ido , T , Kono , K , Peng , Y , Osawa , Y , Yatomi , G , Kidani , A , Kudo , M , Hiraka , R , Takeda , K , Bell , R E , Maan , A , Boyle , D P , Majeski , R , Soukhanovskii , V , Groth , M , McLean , A , Wilcox , R S , Lasnier , C , Nakamura , K , Nagashima , Y , Ikezoe , R , Hasegawa , M , Kuroda , K , Higashijima , A , Nagata , T , Shimabukuro , S , Niiya , I , Sekiya , I & Hasuo , M 2023 , ' Spectroscopic measurement of increases in hydrogen molecular rotational temperature with plasma-facing surface temperature and due to collisional-radiative processes in tokamaks ' , Nuclear Fusion , vol. 63 , no. 9 , 096004 , pp. 1-16 . https://doi.org/10.1088/1741-4326/acd4d1