Interpretation of Lyman opacity measurements in JET with the ITER-like wall using a particle balance approach
Abstract
Recent measurements of the Lyβ/Dα ratio in the JET ITER-like wall (ILW) divertor show comparatively more pronounced Lyβ reabsorption relative to previous results in JET with the carbon wall (JET-C). At the outer horizontal target ion current rollover point a Lyβ reabsorption rate of 60% is measured, increasing to 80% in more pronounced detachment, implying a Lyα reabsorption rate of 90%–98%. The radially resolved Lyβ/Dα measurements are used to constrain Lyman opacity corrections to atomic rate coefficients using the population escape factor technique in order to capture the local changes to the excited state population structure in the high Lyman opacity regions at and outboard of the outer strike point. To check the self-consistency of the Lyman opacity measurements, a detailed spectroscopic interpretation of the outer divertor particle balance is presented, in which the impact of opacity corrections to the Lyα inverse photon efficiency coefficients is assessed. A five-fold deficit in the estimated D+ source rate obtained with optically thin plasma assumptions is reconciled once the opacity corrections are factored into the Lyα photon rate to ionization rate conversion. The experiment results are reproduced in EDGE2D-EIRENE density scan simulations in which an imposed ad hoc Lyman reabsorption rate is recoveredmore »
- Authors:
-
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Aalto Univ., Otaniemi (Finland)
- Culham Science Centre, Abingdon (United Kingdom). Culham Centre for Fusion Energy (CCFE), EURATOM/UKAEA Fusion Association
- Univ. of Strathclyde, Glasgow (United Kingdom)
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1649521
- Grant/Contract Number:
- AC05-00OR22725
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Plasma Physics and Controlled Fusion
- Additional Journal Information:
- Journal Volume: 62; Journal Issue: 6; Journal ID: ISSN 0741-3335
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Lomanowski, Bartosz A., Groth, M., Coffey, Ivor, Karhunen, Juuso, Maggi, Costanza, Meigs, Andrew, Menmuir, Sheena, and O mullane, Martin. Interpretation of Lyman opacity measurements in JET with the ITER-like wall using a particle balance approach. United States: N. p., 2020.
Web. doi:10.1088/1361-6587/ab7432.
Lomanowski, Bartosz A., Groth, M., Coffey, Ivor, Karhunen, Juuso, Maggi, Costanza, Meigs, Andrew, Menmuir, Sheena, & O mullane, Martin. Interpretation of Lyman opacity measurements in JET with the ITER-like wall using a particle balance approach. United States. https://doi.org/10.1088/1361-6587/ab7432
Lomanowski, Bartosz A., Groth, M., Coffey, Ivor, Karhunen, Juuso, Maggi, Costanza, Meigs, Andrew, Menmuir, Sheena, and O mullane, Martin. Mon .
"Interpretation of Lyman opacity measurements in JET with the ITER-like wall using a particle balance approach". United States. https://doi.org/10.1088/1361-6587/ab7432. https://www.osti.gov/servlets/purl/1649521.
@article{osti_1649521,
title = {Interpretation of Lyman opacity measurements in JET with the ITER-like wall using a particle balance approach},
author = {Lomanowski, Bartosz A. and Groth, M. and Coffey, Ivor and Karhunen, Juuso and Maggi, Costanza and Meigs, Andrew and Menmuir, Sheena and O mullane, Martin},
abstractNote = {Recent measurements of the Lyβ/Dα ratio in the JET ITER-like wall (ILW) divertor show comparatively more pronounced Lyβ reabsorption relative to previous results in JET with the carbon wall (JET-C). At the outer horizontal target ion current rollover point a Lyβ reabsorption rate of 60% is measured, increasing to 80% in more pronounced detachment, implying a Lyα reabsorption rate of 90%–98%. The radially resolved Lyβ/Dα measurements are used to constrain Lyman opacity corrections to atomic rate coefficients using the population escape factor technique in order to capture the local changes to the excited state population structure in the high Lyman opacity regions at and outboard of the outer strike point. To check the self-consistency of the Lyman opacity measurements, a detailed spectroscopic interpretation of the outer divertor particle balance is presented, in which the impact of opacity corrections to the Lyα inverse photon efficiency coefficients is assessed. A five-fold deficit in the estimated D+ source rate obtained with optically thin plasma assumptions is reconciled once the opacity corrections are factored into the Lyα photon rate to ionization rate conversion. The experiment results are reproduced in EDGE2D-EIRENE density scan simulations in which an imposed ad hoc Lyman reabsorption rate is recovered spectroscopically using synthetic measurements, and a similar shortfall in the D+ source rate estimates is reconciled using Lyman opacity corrected atomic data. The model limitations prevent a more detailed self-consistent analysis of the Lyman opacity impact on divertor parameters and detachment evolution, and hence motivate renewed efforts to re-establish routine exploitation of the photon transport modelling capabilities in the EIRENE code package. Lyman opacity corrections to atomic data coefficients are necessary for spectroscopic interpretation of the JET-ILW divertor plasma, with significant influence on the divertor plasma also a likely consequence of the presence of strong Lyα reabsorption. Finally, a scan of auxiliary heating powers spanning L-mode and H-mode conditions reveals a strong correlation of the measured Lyβ opacity with the outer target temperature, suggesting new possibilities for using Lyman opacity measurements in establishing detachment scalings.},
doi = {10.1088/1361-6587/ab7432},
journal = {Plasma Physics and Controlled Fusion},
number = 6,
volume = 62,
place = {United States},
year = {Mon Apr 27 00:00:00 EDT 2020},
month = {Mon Apr 27 00:00:00 EDT 2020}
}
Web of Science
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