Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum

Chrobak, C. P.; Doerner, R. P.; Stangeby, P. C.; Wampler, W. R.; Rudakov, D. L.; Wright, G. M.; Abrams, T.; Ding, R.; Elder, J. D.; Guterl, J.; Guo, H. Y.; Lasnier, C.; Thomas, D. M.; Leonard, A. W.; Buchenauer, D. A.; McLean, A. G.; Watkins, J. G.; Tynan, G. R.

doi:10.1016/j.nme.2016.11.033

Title: Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum

Abstract

Here, we present measurements and modeling of aluminum erosion and redeposition experiments in separate helium and deuterium low power, low density L-mode plasmas at the outer divertor strike point of DIII-D to provide a low-Z material benchmark dataset for tokamak erosion-deposition modeling codes. Coatings of Al ~100nm thick were applied to ideal (smooth) and realistic (rough) surfaces and exposed to repeat plasma discharges using the DiMES probe. Redeposition and re-erosion in all cases was primarily in the downstream toroidal field direction, evident from both in-situ spectroscopic and post-mortem non spectroscopic measurements. The gross Al erosion yield estimated from both He and D plasma exposures was ~40-70% of the expected erosion yield based on theoretical physical sputtering yields. However, the multi-step redeposition and re-erosion process, and hence the measured net erosion yield and material migration, was found to be influenced by the surface roughness and/or porosity. On rough surfaces, the fraction of the eroded Al coating found redeposited outside the original coating area was 25x higher than on smooth surfaces. The amount of Al found redeposited on the rough substrate was in fact proportional to the net eroded Al, suggesting an accumulation of deposited Al in surface pores and other areasmore »« less

Authors:: Chrobak, C. P.; Doerner, R. P.; Stangeby, P. C.; Wampler, W. R.; Rudakov, D. L.; Wright, G. M.; Abrams, T.; Ding, R.; Elder, J. D.; Guterl, J.; Guo, H. Y.; Lasnier, C.; Thomas, D. M.; Leonard, A. W.; Buchenauer, D. A.; McLean, A. G.; Watkins, J. G.; Tynan, G. R.

Publication Date:: Tue Aug 01 00:00:00 EDT 2017

Research Org.:: General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:: 1341466

Alternate Identifier(s):: OSTI ID: 1372469; OSTI ID: 1860665

Report Number(s):: LLNL-JRNL-830747
Journal ID: ISSN 2352-1791; S2352179116301387; PII: S2352179116301387

Grant/Contract Number:: FC02-04ER54698; SC0001961; AC04-94AL85000; AC52-07NA27344; FG02-94ER52435

Resource Type:: Published Article

Journal Name:: Nuclear Materials and Energy

Additional Journal Information:: Journal Name: Nuclear Materials and Energy Journal Volume: 12 Journal Issue: C; Journal ID: ISSN 2352-1791

Publisher:: Elsevier

Country of Publication:: Netherlands

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; erosion; deposition; migration; roughness; aluminum; mixed materials

Citation Formats


                    Chrobak, C. P., Doerner, R. P., Stangeby, P. C., Wampler, W. R., Rudakov, D. L., Wright, G. M., Abrams, T., Ding, R., Elder, J. D., Guterl, J., Guo, H. Y., Lasnier, C., Thomas, D. M., Leonard, A. W., Buchenauer, D. A., McLean, A. G., Watkins, J. G., and Tynan, G. R. Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum.  Netherlands: N. p., 2017. 
Web.  doi:10.1016/j.nme.2016.11.033.

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                    Chrobak, C. P., Doerner, R. P., Stangeby, P. C., Wampler, W. R., Rudakov, D. L., Wright, G. M., Abrams, T., Ding, R., Elder, J. D., Guterl, J., Guo, H. Y., Lasnier, C., Thomas, D. M., Leonard, A. W., Buchenauer, D. A., McLean, A. G., Watkins, J. G., & Tynan, G. R. Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum.  Netherlands.  https://doi.org/10.1016/j.nme.2016.11.033

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                    Chrobak, C. P., Doerner, R. P., Stangeby, P. C., Wampler, W. R., Rudakov, D. L., Wright, G. M., Abrams, T., Ding, R., Elder, J. D., Guterl, J., Guo, H. Y., Lasnier, C., Thomas, D. M., Leonard, A. W., Buchenauer, D. A., McLean, A. G., Watkins, J. G., and Tynan, G. R. Tue .  
"Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum".  Netherlands.  https://doi.org/10.1016/j.nme.2016.11.033.

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@article{osti_1341466,

  title        = {Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum},

  author       = {Chrobak, C. P. and Doerner, R. P. and Stangeby, P. C. and Wampler, W. R. and Rudakov, D. L. and Wright, G. M. and Abrams, T. and Ding, R. and Elder, J. D. and Guterl, J. and Guo, H. Y. and Lasnier, C. and Thomas, D. M. and Leonard, A. W. and Buchenauer, D. A. and McLean, A. G. and Watkins, J. G. and Tynan, G. R.},

  abstractNote = {Here, we present measurements and modeling of aluminum erosion and redeposition experiments in separate helium and deuterium low power, low density L-mode plasmas at the outer divertor strike point of DIII-D to provide a low-Z material benchmark dataset for tokamak erosion-deposition modeling codes. Coatings of Al ~100nm thick were applied to ideal (smooth) and realistic (rough) surfaces and exposed to repeat plasma discharges using the DiMES probe. Redeposition and re-erosion in all cases was primarily in the downstream toroidal field direction, evident from both in-situ spectroscopic and post-mortem non spectroscopic measurements. The gross Al erosion yield estimated from both He and D plasma exposures was ~40-70% of the expected erosion yield based on theoretical physical sputtering yields. However, the multi-step redeposition and re-erosion process, and hence the measured net erosion yield and material migration, was found to be influenced by the surface roughness and/or porosity. On rough surfaces, the fraction of the eroded Al coating found redeposited outside the original coating area was 25x higher than on smooth surfaces. The amount of Al found redeposited on the rough substrate was in fact proportional to the net eroded Al, suggesting an accumulation of deposited Al in surface pores and other areas shadowed from re-erosion. In order to determine the fraction and distribution of eroded Al returning to the surface, a simple model for erosion and redeposition was developed and fitted to the measurements. The model presented here reproduces many of the observed results in these experiments by using theoretically calculated sputtering yields, calculating surface composition changes and erosion rates in time, assuming a spatial distribution function for redepositing atoms, and accounting for deposit trapping in pores. The results of the model fits reveal that total redeposition fraction increases with higher plasma temperature (~30% for 15-18eV plasmas, and ~45% for 25-30eV plasmas), and that 50% of the atoms redepositing on rough surfaces accumulated in shadowed areas.},

  doi          = {10.1016/j.nme.2016.11.033},

  journal      = {Nuclear Materials and Energy},

  number       = C,

  volume       = 12,

  place        = {Netherlands},

  year         = {Tue Aug 01 00:00:00 EDT 2017},

  month        = {Tue Aug 01 00:00:00 EDT 2017}

}

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Measurement and modeling of aluminum sputtering and ionization in the DIII-D divertor including magnetic pre-sheath effects
journal, August 2018

Chrobak, C. P.; Stangeby, P. C.; Hollmann, E.
Nuclear Fusion, Vol. 58, Issue 10
DOI: 10.1088/1741-4326/aad4c9

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Title: Characterizing Low-Z erosion and deposition in the DIII-D divertor using aluminum

Abstract

Citation Formats

Measurement and modeling of aluminum sputtering and ionization in the DIII-D divertor including magnetic pre-sheath effects journal, August 2018

Measurement and modeling of aluminum sputtering and ionization in the DIII-D divertor including magnetic pre-sheath effects
journal, August 2018