Comparison of heat flux measurement techniques during the DIII-D metal ring campaign

Barton, Jo L.; Nygren, R. E.; Unterberg, E. A.; Watkins, J. G.; Makowski, M. A.; Moser, A.; Rudakov, D. L.; Buchenauer, D.

doi:10.1088/1402-4896/aa878a

Title: Comparison of heat flux measurement techniques during the DIII-D metal ring campaign

Abstract

The heat fluxes expected in the ITER divertor raise concerns about the damage tolerances of tungsten, especially due to thermal transients caused by edge localized modes (ELMs) as well as frequent temperature cycling from high to low extremes. Thus we are motivated to understand the heat flux conditions that can cause not only enhanced erosion but also bulk thermo-mechanical damage to a tungsten divertor. For the metal ring campaign in DIII-D, tungsten-coated TZM tile inserts were installed making two toroidal arrays of metal tile inserts in the lower divertor. This study examines the deposited heat flux on these rings with embedded thermocouples (TCs) sampling at 10 kHz and compares them to Langmuir probe (LP) and infrared thermography (IRTV) heat flux measurements. We see agreement of the TC, LP, and IRTV data within 20% of the heat flux averaged over the entire discharge, and that all three diagnostics suggest parallel heat flux at the OSP location increases linearly with input heating power. The TC and LP heat flux time traces during the discharge trend together during large changes to the average heat flux. By subtracting the LP measured inter-ELM heat flux from TC data, using a rectangular ELM energy pulse shape,more »« less

Authors:

Barton, Jo L. ^[1]; Nygren, R. E. ^[1];

^[2]; Watkins, J. G. ^[1]; Makowski, M. A. ^[3]; Moser, A. ^[4]; Rudakov, D. L. ^[5]; Buchenauer, D. ^[1]

Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
General Atomics, San Diego, CA (United States)
Univ. of California, San Diego, CA (United States)

Publication Date:: Wed Sep 13 00:00:00 EDT 2017

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:: 1513373

Grant/Contract Number:: AC05-00OR22725

Resource Type:: Journal Article: Accepted Manuscript

Journal Name:: Physica Scripta

Additional Journal Information:: Journal Volume: T170; Journal Issue: T170; Journal ID: ISSN 0031-8949

Publisher:: IOP Publishing

Country of Publication:: United States

Language:: English

Subject:: 42 ENGINEERING; plasma facing components; heat flux; ELMs

Citation Formats


                    Barton, Jo L., Nygren, R. E., Unterberg, E. A., Watkins, J. G., Makowski, M. A., Moser, A., Rudakov, D. L., and Buchenauer, D. Comparison of heat flux measurement techniques during the DIII-D metal ring campaign.  United States: N. p., 2017. 
        Web.  doi:10.1088/1402-4896/aa878a.

Copy to clipboard


                    Barton, Jo L., Nygren, R. E., Unterberg, E. A., Watkins, J. G., Makowski, M. A., Moser, A., Rudakov, D. L., & Buchenauer, D. Comparison of heat flux measurement techniques during the DIII-D metal ring campaign.  United States.  https://doi.org/10.1088/1402-4896/aa878a

Copy to clipboard


                    Barton, Jo L., Nygren, R. E., Unterberg, E. A., Watkins, J. G., Makowski, M. A., Moser, A., Rudakov, D. L., and Buchenauer, D. 2017.  
        "Comparison of heat flux measurement techniques during the DIII-D metal ring campaign".  United States.  https://doi.org/10.1088/1402-4896/aa878a.  https://www.osti.gov/servlets/purl/1513373.

Copy to clipboard


                    
@article{osti_1513373,

  title        = {Comparison of heat flux measurement techniques during the DIII-D metal ring campaign},

  author       = {Barton, Jo L. and Nygren, R. E. and Unterberg, E. A. and Watkins, J. G. and Makowski, M. A. and Moser, A. and Rudakov, D. L. and Buchenauer, D.},

  abstractNote = {The heat fluxes expected in the ITER divertor raise concerns about the damage tolerances of tungsten, especially due to thermal transients caused by edge localized modes (ELMs) as well as frequent temperature cycling from high to low extremes. Thus we are motivated to understand the heat flux conditions that can cause not only enhanced erosion but also bulk thermo-mechanical damage to a tungsten divertor. For the metal ring campaign in DIII-D, tungsten-coated TZM tile inserts were installed making two toroidal arrays of metal tile inserts in the lower divertor. This study examines the deposited heat flux on these rings with embedded thermocouples (TCs) sampling at 10 kHz and compares them to Langmuir probe (LP) and infrared thermography (IRTV) heat flux measurements. We see agreement of the TC, LP, and IRTV data within 20% of the heat flux averaged over the entire discharge, and that all three diagnostics suggest parallel heat flux at the OSP location increases linearly with input heating power. The TC and LP heat flux time traces during the discharge trend together during large changes to the average heat flux. By subtracting the LP measured inter-ELM heat flux from TC data, using a rectangular ELM energy pulse shape, and taking the relative size and duration of each ELM from ${{D}}_{\alpha }$ measurements, we extract the ELM heat fluxes from TC data. This over-estimates the IRTV measured ELM heat fluxes by a factor of 1.9, and could be due to the simplicity of the TC heat flux model and the assumed ELM energy pulse shape. ELM heat fluxes deposited on the inserts are used to model tungsten erosion in this campaign. These TC ELM heat flux estimates are used in addition to IRTV, especially in cases where the IRTV view to the metal ring is obstructed. We observe that some metal inserts were deformed due to exposed leading edges. The thermal conditions on these inserts are investigated with the thermal modeling code ABAQUS using our heat flux measurements when these edges were exposed. We report on how the thermal cycling on the ends of the inserts caused this deformation.},

  doi          = {10.1088/1402-4896/aa878a},

  url          = {https://www.osti.gov/biblio/1513373},
  journal      = {Physica Scripta},

  issn         = {0031-8949},

  number       = T170,

  volume       = T170,

  place        = {United States},

  year         = {Wed Sep 13 00:00:00 EDT 2017},

  month        = {Wed Sep 13 00:00:00 EDT 2017}

}

Copy to clipboard

Journal Article:

Free Publicly Available Full Text

Accepted Manuscript (DOE)

Publisher's Version of Record

https://doi.org/10.1088/1402-4896/aa878a

Other availability

Search WorldCat to find libraries that may hold this journal

Citation Metrics:

Cited by: 5 works

Citation information provided by
Web of Science

Figures / Tables:

Figure 1: Schematic layout of experiment. The floor and shelf insert locations are highlighted in the divertor along with the diagnostic locations. Black circles indicate the Langmuir probe locations, orange vertical bars indicate the thermocouple locations, and the IRTV scans across the entire divertor. In this experiment, the IRTV viewmore »

All figures and tables (10 total)

Save / Share:

Export Metadata

Save to My Library

Figures / Tables found in this record:

Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.

Similar records in OSTI.GOV collections:

Impact of divertor material on neutral recycling and discharge fueling in DIII-D

Journal Article Bykov, I.; Rudakov, D.; Pigarov, A.; ... - Physica Scripta (Online)

We report that experiments with the lower divertor of DIII-D during the Metal Rings Campaign (MRC) show that the fraction F of atomic D in the total recycling flux is material-dependent and varies through the ELM cycle, which may affect divertor fueling. Between ELMs, F_C ~ 10% and FW ~ 40%, consistent with expectations if all atomic recycling is due to reflections. During ELMs, F_C increases to 50% and F_W to 60%. In contrast, the total D recycling coefficient including atoms and molecules R stays close to unity near the strike point where the surface is saturated with D. Duringmore »« less
https://doi.org/10.1088/1402-4896/ab5a2e

Full Text Available
The effectiveness of D ₂ pellet injection in reducing intra-ELM and inter-ELM tungsten divertor erosion rates in DIII-D during the Metal Rings Campaign

Journal Article Cacheris, A.; Abrams, T.; Baylor, L.; ... - Plasma Physics and Controlled Fusion

Edge localized modes (ELMs) in H-mode plasmas erode plasma-facing components (PFCs) and lead to impurities in the core, reducing confinement. This study analyzes D₂ pellet injection on the DIII-D fusion experiment used as an ELM mitigation technique applied during the 2016 tungsten Metal Rings Campaign to reduce W erosion during ELMs. The 400.9 nm photon wavelength line emission intensity of tungsten atoms (WI) filterscope channels and Langmuir probes were used to infer the gross erosion rate of tungsten-coated tiles installed in the divertor of DIII-D. D₂ mass injection rates ranging from 34 to 41 arbitrary units (A.U.) and no D₂more »« less
https://doi.org/10.1088/1361-6587/acd026
Divertor erosion in DIII-D

Conference Whyte, D; Bastasz, R; Wampler, W; ...

Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point (OSP) of two divertor plasma conditions: attached (T{sub e} > 40 eV) ELMing plasmas, and detached (T{sub e} < 2 eV) ELMing plasmas. For the attached cases, the erosion rates exceed 10 cm/exposure-year, even with incident heat flux < 1 MW/m{sup 2}. In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport andmore »« less
https://doi.org/10.2172/654183

Full Text Available
Thermal management of tungsten leading edges in DIII-D

Journal Article Nygren, Richard; Rudakov, Dmitry; Murphy, Christopher; ... - Fusion Engineering and Design

The DiMES materials probe exposed tungsten blocks with 0.3 and 1 mm high leading edges to DIII-D He plasmas in 2015 and 2016 viewed with high resolution IRTV. The 1-mm edge may have reached >2400° C in a 3-s shot with a (parallel) heat load of ~50 MW/m² and ~10 MW/m² on the surface based on modeling. The experiments support ITER. Leading edges were also a concern in the DIII-D Metal Tile Experiment in 2016. Two toroidal rings of divertor tiles had W-coated molybdenum inserts 50 mm wide radially. This study presents data and thermal analyses.
Cited by 2
https://doi.org/10.1016/j.fusengdes.2017.04.060

Full Text Available
Modeling of ExB effects on tungsten re-deposition and transport in the DIII-D divertor

Journal Article Nichols, J.; Abrams, T.; Chrobak, C.; ... - Nuclear Fusion

Mixed-material DIVIMP-WallDYN modelling, now incorporating ExB drifts, is presented that simultaneously reproduces tungsten (W) erosion and deposition patterns observed during the DIII-D Metal Rings Campaign, in which a toroidally symmetric set of W-coated tiles were installed in the carbon (C) DIII-D divertor. Since most reactor plasma facing component (PFC) designs call for mixed-material environments, including ITER’s W/Be enviroment, the divertor targets will quickly evolve into reconstitued surfaces of multiple elements. This work identifies controlling physics that affects material migration patterns in the divertor, which impact PFC lifetimes and impurity leakage from the divertor to the core. These simulations indicate thatmore »« less
https://doi.org/10.1088/1741-4326/ac14e6

Full Text Available

Similar Records