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

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.

doi:10.1088/1741-4326/abaf31

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

Journal Article · Mon Sep 28 00:00:00 EDT 2020 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/abaf31· OSTI ID:1871400

^[1]; Maingi, R. ^[1]; Nagy, A. ^[1]; Ren, J. ^[2]; Duran, J. D. ^[2]; Maan, A. ^[2]; Donovan, D. C. ^[2]; Boedo, J. A. ^[3];

^[3]; Hyatt, A. W. ^[4]; Wilks, T. W. ^[5]; Shafer, M. W. ^[6]; Samuell, C. M. ^[7]; Fenstermacher, M. E. ^[7]; Gilson, E. P. ^[1];

^[1]; Mansfield, D. K. ^[1]; Abrams, T. ^[4];

^[1]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Univ. of Tennessee, Knoxville, TN (United States)
Univ. of California, San Diego, CA (United States)
General Atomics, San Diego, CA (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

In this paper, 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 (GDB). Isotopically enriched B powder (B¹¹ > 95%) was introduced gravitationally in a sequence of H-mode plasma discharges at rates up to ~160 mg s^-1 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 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 GDB.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Contributing Organization:: DIII-D Team

Grant/Contract Number:: AC52-07NA27344; FC02-04ER54698; AC02-09CH11466; FG02-07ER54917; AC05-00OR22725; SC0014264

OSTI ID:: 1871400

Alternate ID(s):: OSTI ID: 1668115; OSTI ID: 1668799; OSTI ID: 1674947

Report Number(s):: LLNL-JRNL-834531; 2020_257; 1051385; TRN: US2306749

Journal Information:: Nuclear Fusion, Vol. 60, Issue 12; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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