Plasma-parameter dependence of ro-vibrational temperatures for H2 in LHD divertor

Fujii, Keisuke; Oshioka, Tsubasa; Niihama, Atsushi; Kuzmin, Arseniy; Shikama, Taiichi; Kobayashi, Masahiro; Hasuo, Masahiro

doi:10.1016/j.jqsrt.2023.108751

Cited by 2 publications

(4 citation statements)

References 30 publications

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“…Analysis of the D * 2 Fulcher band emisson to infer rotational and vibrational distributions has been performed on a range of different devices in the past, including tokamaks (JET [52], DIII-D [30], ASDEX-Upgrade [53] and JT60-U [54]), as well as other devices such as LHD [47] and Magnum-PSI [55]. Generally, a Boltzmann distribution is found for the rotational distribution across the various devices.…”

Section: Relevance and Implications Of Our Resultsmentioning

confidence: 99%

“…A large range of different rotational temperatures are quoted in literature, ranging from less than 1000 K (mainly linear devices) to 10 000 K and higher [30]. In multiple devices an increase of the rotational temperature with the electron density is observed, noteably JET [52], DIII-D [30] and LHD [47]. Hollmann et al [30] shows similar rotational temperatures, at the same electron density, for DIII-D, TEXTOR (limiter, no divertor) as well as for a linear device, PISCES [30].…”

Section: Relevance and Implications Of Our Resultsmentioning

confidence: 99%

“…This change in vibrational distribution seems to occur simultaneously with a change in rotational temperature, as indicated in figure 16. Changes to the vibrational distribution as the rotational temperature is altered are seen in literature [46,47], where a correlation between the vibrational temperature and the rotational temperature is observed. However, higher vibrational temperatures result in a relative decrease of ν = 1, 2, 3 compared to ν = 0, which is in contrast to our MAST-U observations in figure 16.…”

Section: The Vibrational Distribution Of D 2 In the Mast-u Divertormentioning

confidence: 90%

“…As such a vibrational temperature cannot be simply assigned but it is worth noting here that previous studies (when able to assign a vibrational temperature) have found correlation between electron density and vibrational temperature [46,47].…”

Section: The Vibrational Distribution Of D 2 In the Mast-u Divertormentioning

confidence: 91%

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Initial Fulcher band observations from high resolution spectroscopy in the MAST-U divertor

Osborne,

Verhaegh,

Bowden

et al. 2023

Plasma Phys. Control. Fusion

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High resolution D 2 ∗ Fulcher band spectroscopy was used in the MAST-U divertors during Super-X and (shorter-legged) elongated divertor density ramps with D 2 fuelling from the mid-plane high-field side. In the Super-X case, the upper divertor showed ground state rotational temperatures of the D 2 molecules increasing from ~6000 K, starting at the detachment onset, to ~9000 K during deepening detachment. This was correlated with the movement of the Fulcher emission region towards the X-point, which is in turn correlated with the movement of the ionisation source. The increase in rotational temperature occurred throughout the divertor except near the divertor entrance, where ionisation was still the dominant process. Qualitative agreement was obtained between the lower and upper divertor. Similar rotational temperatures were obtained in the elongated divertor before the detachment onset, although the increase in rotational temperature during detachment was less clearly observed as less deep detachment was obtained. The measured vibrational distribution of the upper Fulcher state does not agree with a ground state Boltzmann distribution but shows a characteristically elevated population in the ν = 2 and ν = 3 bands in particular; which is strongly correlated to the rotational temperature.

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Section: Relevance and Implications Of Our Resultsmentioning

confidence: 99%

Section: Relevance and Implications Of Our Resultsmentioning

confidence: 99%

Section: The Vibrational Distribution Of D 2 In the Mast-u Divertormentioning

confidence: 90%

Section: The Vibrational Distribution Of D 2 In the Mast-u Divertormentioning

confidence: 91%

See 2 more Smart Citations

Initial Fulcher band observations from high resolution spectroscopy in the MAST-U divertor

Osborne,

Verhaegh,

Bowden

et al. 2023

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

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Experimental validation of a collision-radiation dataset for molecular hydrogen in plasmas

Fujii,

Sawada,

Kuzmin

et al. 2024

Physics of Plasmas

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Quantitative spectroscopy of molecular hydrogen has generated substantial demand, leading to the accumulation of diverse elementary process data encompassing radiative transitions, electron-impact transitions, predissociations, and quenching. However, their rates currently available are still sparse, and there are inconsistencies among those proposed by different authors. In this study, we demonstrate an experimental validation of such a molecular dataset by composing a collisional-radiative model (CRM) for molecular hydrogen and comparing experimentally obtained vibronic populations across multiple levels. From the population kinetics of molecular hydrogen, the importance of each elementary process in various parameter space is studied. In low-density plasmas (electron density ne≲1017 m−3) the excitation rates from the ground states and radiative decay rates, both of which have been reported previously, determine the excited state population. The inconsistency in the excitation rates affects the population distribution the most significantly in this parameter space. However, in higher density plasmas (ne≳1018 m−3), the excitation rates from excited states become important, which have never been reported in the literature, and may need to be approximated in some way. In order to validate these molecular datasets and approximated rates, we carried out experimental observations for two different hydrogen plasmas; a low-density radio frequency heated plasma (ne≈1016 m−3) and the Large Helical Device (LHD) divertor plasma (ne≳1018 m−3). The visible emission lines from EF1Σg+, HH¯1Σg+, D1Πu±, GK1Σg+, I1Πg±, J1Δg±, h3Σg+, e3Σu+, d3Πu±,g3Σg+, i3Πg±, and j3Δg± states were observed simultaneously and their population distributions were obtained from their intensities. We compared the observed population distributions with the CRM prediction, in particular the CRM with the rates compiled by Janev et al., Miles et al., and those calculated with the molecular convergent close-coupling (MCCC) method. The MCCC prediction gives the best agreement with the experiment, particularly for the emission from the low-density plasma. However, the population distribution in the LHD divertor shows a worse agreement with the CRM than those from low-density plasma, indicating the necessity of the precise excitation rates from excited states. We also found that the rates for the electron attachment is inconsistent with experimental results. This requires further investigation.

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Plasma-parameter dependence of ro-vibrational temperatures for H2 in LHD divertor

Cited by 2 publications

References 30 publications

Initial Fulcher band observations from high resolution spectroscopy in the MAST-U divertor

Initial Fulcher band observations from high resolution spectroscopy in the MAST-U divertor

Experimental validation of a collision-radiation dataset for molecular hydrogen in plasmas

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