Investigation of the role of hydrogen molecules in 1D simulation of divertor detachment

Zhou, Yulin; Dudson, Benjamin; Militello, Fulvio; Verhaegh, Kevin; Myatra, Omkar

doi:10.1088/1361-6587/ac6827

Investigation of the role of hydrogen molecules in 1D simulation of divertor detachment

Journal Article · Tue May 10 00:00:00 EDT 2022 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/ac6827· OSTI ID:1868156

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Univ. of York (United Kingdom); Southwestern Institute of Physics, Chengdu (China)
Univ. of York (United Kingdom); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Culham Science Centre, Abingdon (United Kingdom)

The role of neutral and charged hydrogenic molecules in detached regimes of tokamak plasmas is investigated using a simplified 1D numerical model. Using MAST Upgrade like conditions, simulations are implemented to study the rollover of target flux Γ in upstream density scan. It is found that if H₂ and H₂+ are considered in simulations a lower target temperature and a larger upstream density will be required to trigger divertor detachment under the same input power and particle flux, and the critical detachment threshold (the critical ratio of upstream static pressure to the power entering the recycling region) is found to be $$^{ρ_{up}}_{ρ_{recl}}$$ ~ 8.1 NMW^-1 at rollover. Molecule–plasma interactions are found to be as crucial as atom–plasma interactions during divertor detachment, both of which account for the majority of plasma momentum loss in the cases studied here. Further analysis of the momentum loss decomposition shows molecule-plasma elastic collisions dominate molecule-plasma interactions, while molecular charge exchange cannot effectively reduce plasma momentum. In terms of H_alpha emission, a strong rise of H_alpha signal is found to be due to molecular excitation channels when the upstream density further increases after rollover.

View Accepted Manuscript (DOE)

Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: China Scholarship Council; National Magnetic Confinement Fusion Research Program of China; National Natural Science Foundation of China; RCUK Energy Programme; USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: AC52-07NA27344

OSTI ID:: 1868156

Report Number(s):: LLNL-JRNL-826561; 1041286

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 6 Vol. 64; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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