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Title: Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas

Abstract

We report observations from the DIII-D tokamak indicating that boron (B) powder injection in tokamak plasmas improves wall conditions similarly to glow discharge boronization. Isotopically enriched B powder (B11>95%) was introduced gravitationally in a sequence of H-mode plasma discharges at rates up to ~160 mg/s for durations up to 3 s. Boron injection to cumulative amounts ≤0.1 g appeared to improve wall conditions similarly to boronization, with indications of reduced wall fueling, reduced recycling at the outer strike point and reduced impurity content at breakdown. Post-mortem analysis of graphite samples exposed to far scrape-off layer (SOL) plasma fluxes during boron injection confirm the formation of a B-C layer, with average surface composition B:C~1. The results suggest that injecting boron-rich powders in tokamak plasmas can effectively replenish boron films on carbon plasma facing components to improve wall conditions and extend the duration of the beneficial effects of glow discharge boronization.

Authors:
ORCiD logo [1];  [1];  [1];  [2];  [2];  [2];  [2];  [3]; ORCiD logo [3];  [4];  [5];  [6];  [7];  [7];  [1]; ORCiD logo [1];  [1];  [4]; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Univ. of California, San Diego, CA (United States)
  4. General Atomics, San Diego, CA (United States)
  5. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  7. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Contributing Org.:
DIII-D Team
OSTI Identifier:
1668799
Alternate Identifier(s):
OSTI ID: 1668115; OSTI ID: 1674947
Report Number(s):
2020_257
Journal ID: ISSN 0029-5515
Grant/Contract Number:  
SC0014264; AC05-00OR22725; AC02-09CH11466; FC02-04ER54698; AC52-07NA27344; FG02-07ER54917
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 60; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
wall conditioning; boronization; powder; dropper; DIII-D; boron

Citation Formats

Bortolon, A., Maingi, R., Nagy, A., Ren, J., Duran, J. D., Maan, A., Donovan, D. C., Boedo, J. A., Rudakov, D. L., Hyatt, A. W., Wilks, T. W., Shafer, M. W., Samuell, C. M., Fenstermacher, M. E., Gilson, E. P., Lunsford, R., Mansfield, D. K., Abrams, T., and Nazikian, R. Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas. United States: N. p., 2020. Web. doi:10.1088/1741-4326/abaf31.
Bortolon, A., Maingi, R., Nagy, A., Ren, J., Duran, J. D., Maan, A., Donovan, D. C., Boedo, J. A., Rudakov, D. L., Hyatt, A. W., Wilks, T. W., Shafer, M. W., Samuell, C. M., Fenstermacher, M. E., Gilson, E. P., Lunsford, R., Mansfield, D. K., Abrams, T., & Nazikian, R. Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas. United States. doi:10.1088/1741-4326/abaf31.
Bortolon, A., Maingi, R., Nagy, A., Ren, J., Duran, J. D., Maan, A., Donovan, D. C., Boedo, J. A., Rudakov, D. L., Hyatt, A. W., Wilks, T. W., Shafer, M. W., Samuell, C. M., Fenstermacher, M. E., Gilson, E. P., Lunsford, R., Mansfield, D. K., Abrams, T., and Nazikian, R. Mon . "Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas". United States. doi:10.1088/1741-4326/abaf31.
@article{osti_1668799,
title = {Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas},
author = {Bortolon, A. and Maingi, R. and Nagy, A. and Ren, J. and Duran, J. D. and Maan, A. and Donovan, D. C. and Boedo, J. A. and Rudakov, D. L. and Hyatt, A. W. and Wilks, T. W. and Shafer, M. W. and Samuell, C. M. and Fenstermacher, M. E. and Gilson, E. P. and Lunsford, R. and Mansfield, D. K. and Abrams, T. and Nazikian, R.},
abstractNote = {We report observations from the DIII-D tokamak indicating that boron (B) powder injection in tokamak plasmas improves wall conditions similarly to glow discharge boronization. Isotopically enriched B powder (B11>95%) was introduced gravitationally in a sequence of H-mode plasma discharges at rates up to ~160 mg/s for durations up to 3 s. Boron injection to cumulative amounts ≤0.1 g appeared to improve wall conditions similarly to boronization, with indications of reduced wall fueling, reduced recycling at the outer strike point and reduced impurity content at breakdown. Post-mortem analysis of graphite samples exposed to far scrape-off layer (SOL) plasma fluxes during boron injection confirm the formation of a B-C layer, with average surface composition B:C~1. The results suggest that injecting boron-rich powders in tokamak plasmas can effectively replenish boron films on carbon plasma facing components to improve wall conditions and extend the duration of the beneficial effects of glow discharge boronization.},
doi = {10.1088/1741-4326/abaf31},
journal = {Nuclear Fusion},
issn = {0029-5515},
number = 12,
volume = 60,
place = {United States},
year = {2020},
month = {9}
}

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