Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas

G. Bodner; A. Gallo; A. Diallo; R. Lunsford; Ph Moreau; A. Nagy; F. P. Pellissier; C. Guillemaut; J. P. Gunn; C. Bourdelle; C. Desgranges; P. Manas; A. Bortolon; C. C. Klepper; E. Tsitrone; E. A. Unterberg; L. Vermare

doi:10.1088/1741-4326/ac70ea

Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas

G. Bodner, A. Gallo, A. Diallo, R. Lunsford, Ph Moreau, A. Nagy, F. P. Pellissier, C. Guillemaut, J. P. Gunn, C. Bourdelle, C. Desgranges, P. Manas, A. Bortolon, C. C. Klepper, E. Tsitrone, E. A. Unterberg, L. Vermare

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Abstract

Using a recently installed impurity powder dropper (IPD), boron powder (<150 μm) was injected into lower single null (LSN) L-mode discharges in WEST. IPDs possibly enable real-time wall conditioning of the plasma-facing components and may help to facilitate H-mode access in the full-tungsten environment of WEST. The discharges in this experiment featured I p = 0.5 MA, B T = 3.7 T, q 95 = 4.3, t pulse = 12-30 s, n e,0 ∼4 × 1019 m-2, and P LHCD ∼4.5 MW. Estimates of the deuterium and impurity particle fluxes, derived from a combination of visible spectroscopy measurements and their corresponding S/XB coefficients, showed decreases of ∼50% in O+, N+, and C+ populations during powder injection and a moderate reduction of these low-Z impurities (∼50%) and W (∼10%) in the discharges that followed powder injection. Along with the improved wall conditions, WEST discharges with B powder injection observed improved confinement, as the stored energy W MHD, neutron rate, and electron temperature T e increased significantly (10%-25% for W MHD and 60%-200% for the neutron rate) at constant input power. These increases in confinement scale up with the powder drop rate and are likely due to the suppression of ion temperature gradient (ITG) turbulence from changes in Z eff and/or modifications to the electron density profile.

Original language	English
Article number	086020
Journal	Nuclear Fusion
Volume	62
Issue number	8
DOIs	https://doi.org/10.1088/1741-4326/ac70ea
State	Published - Aug 2022

Funding

The authors would like to thank the WEST team and the ORNL PMI group for their support of the IPD experiments (particularly J. Morales, M. De Combarieu, J.F. Artaud, D. Vizinet, C. Gil, A. Grosjean, and C. Johnson), and gratefully acknowledge R. Maingi for useful discussion. This manuscript is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, and has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy. The publisher, by accepting the article for publication acknowledges, that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

Funders	Funder number
U.S. Department of Energy
Office of Science
Fusion Energy Sciences
Princeton University	DE-AC02-09CH11466

Keywords

boronization
impurity injection
powder injection
tungsten
wall conditioning

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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Bodner, G., Gallo, A., Diallo, A., Lunsford, R., Moreau, P., Nagy, A., Pellissier, F. P., Guillemaut, C., Gunn, J. P., Bourdelle, C., Desgranges, C., Manas, P., Bortolon, A., Klepper, C. C., Tsitrone, E., Unterberg, E. A., & Vermare, L. (2022). Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas. Nuclear Fusion, 62(8), Article 086020. https://doi.org/10.1088/1741-4326/ac70ea

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title = "Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas",

abstract = "Using a recently installed impurity powder dropper (IPD), boron powder (<150 μm) was injected into lower single null (LSN) L-mode discharges in WEST. IPDs possibly enable real-time wall conditioning of the plasma-facing components and may help to facilitate H-mode access in the full-tungsten environment of WEST. The discharges in this experiment featured I p = 0.5 MA, B T = 3.7 T, q 95 = 4.3, t pulse = 12-30 s, n e,0 ∼4 × 1019 m-2, and P LHCD ∼4.5 MW. Estimates of the deuterium and impurity particle fluxes, derived from a combination of visible spectroscopy measurements and their corresponding S/XB coefficients, showed decreases of ∼50% in O+, N+, and C+ populations during powder injection and a moderate reduction of these low-Z impurities (∼50%) and W (∼10%) in the discharges that followed powder injection. Along with the improved wall conditions, WEST discharges with B powder injection observed improved confinement, as the stored energy W MHD, neutron rate, and electron temperature T e increased significantly (10%-25% for W MHD and 60%-200% for the neutron rate) at constant input power. These increases in confinement scale up with the powder drop rate and are likely due to the suppression of ion temperature gradient (ITG) turbulence from changes in Z eff and/or modifications to the electron density profile.",

keywords = "boronization, impurity injection, powder injection, tungsten, wall conditioning",

author = "G. Bodner and A. Gallo and A. Diallo and R. Lunsford and Ph Moreau and A. Nagy and Pellissier, {F. P.} and C. Guillemaut and Gunn, {J. P.} and C. Bourdelle and C. Desgranges and P. Manas and A. Bortolon and Klepper, {C. C.} and E. Tsitrone and Unterberg, {E. A.} and L. Vermare",

note = "Publisher Copyright: {\textcopyright} 2022 IAEA, Vienna.",

year = "2022",

month = aug,

doi = "10.1088/1741-4326/ac70ea",

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Bodner, G, Gallo, A, Diallo, A, Lunsford, R, Moreau, P, Nagy, A, Pellissier, FP, Guillemaut, C, Gunn, JP, Bourdelle, C, Desgranges, C, Manas, P, Bortolon, A, Klepper, CC, Tsitrone, E, Unterberg, EA & Vermare, L 2022, 'Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas', Nuclear Fusion, vol. 62, no. 8, 086020. https://doi.org/10.1088/1741-4326/ac70ea

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AU - Bodner, G.

AU - Gallo, A.

AU - Diallo, A.

AU - Lunsford, R.

AU - Moreau, Ph

AU - Nagy, A.

AU - Pellissier, F. P.

AU - Guillemaut, C.

AU - Gunn, J. P.

AU - Bourdelle, C.

AU - Desgranges, C.

AU - Manas, P.

AU - Bortolon, A.

AU - Klepper, C. C.

AU - Tsitrone, E.

AU - Unterberg, E. A.

AU - Vermare, L.

PY - 2022/8

Y1 - 2022/8

N2 - Using a recently installed impurity powder dropper (IPD), boron powder (<150 μm) was injected into lower single null (LSN) L-mode discharges in WEST. IPDs possibly enable real-time wall conditioning of the plasma-facing components and may help to facilitate H-mode access in the full-tungsten environment of WEST. The discharges in this experiment featured I p = 0.5 MA, B T = 3.7 T, q 95 = 4.3, t pulse = 12-30 s, n e,0 ∼4 × 1019 m-2, and P LHCD ∼4.5 MW. Estimates of the deuterium and impurity particle fluxes, derived from a combination of visible spectroscopy measurements and their corresponding S/XB coefficients, showed decreases of ∼50% in O+, N+, and C+ populations during powder injection and a moderate reduction of these low-Z impurities (∼50%) and W (∼10%) in the discharges that followed powder injection. Along with the improved wall conditions, WEST discharges with B powder injection observed improved confinement, as the stored energy W MHD, neutron rate, and electron temperature T e increased significantly (10%-25% for W MHD and 60%-200% for the neutron rate) at constant input power. These increases in confinement scale up with the powder drop rate and are likely due to the suppression of ion temperature gradient (ITG) turbulence from changes in Z eff and/or modifications to the electron density profile.

AB - Using a recently installed impurity powder dropper (IPD), boron powder (<150 μm) was injected into lower single null (LSN) L-mode discharges in WEST. IPDs possibly enable real-time wall conditioning of the plasma-facing components and may help to facilitate H-mode access in the full-tungsten environment of WEST. The discharges in this experiment featured I p = 0.5 MA, B T = 3.7 T, q 95 = 4.3, t pulse = 12-30 s, n e,0 ∼4 × 1019 m-2, and P LHCD ∼4.5 MW. Estimates of the deuterium and impurity particle fluxes, derived from a combination of visible spectroscopy measurements and their corresponding S/XB coefficients, showed decreases of ∼50% in O+, N+, and C+ populations during powder injection and a moderate reduction of these low-Z impurities (∼50%) and W (∼10%) in the discharges that followed powder injection. Along with the improved wall conditions, WEST discharges with B powder injection observed improved confinement, as the stored energy W MHD, neutron rate, and electron temperature T e increased significantly (10%-25% for W MHD and 60%-200% for the neutron rate) at constant input power. These increases in confinement scale up with the powder drop rate and are likely due to the suppression of ion temperature gradient (ITG) turbulence from changes in Z eff and/or modifications to the electron density profile.

KW - boronization

KW - impurity injection

KW - powder injection

KW - tungsten

KW - wall conditioning

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DO - 10.1088/1741-4326/ac70ea

M3 - Article

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SN - 0029-5515

VL - 62

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 8

M1 - 086020

ER -

Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas

Abstract

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Keywords

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