Advances in boronization on NSTX-Upgrade

Skinner, C.H.; Bedoya, F.; Scotti, F.; Allain, Jean Paul; Blanchard, W.; Cai, D.; Jaworski, M. A.; Koel, Bruce E.

doi:10.1016/j.nme.2016.11.024

Cited by 15 publications

(11 citation statements)

References 14 publications

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“…1(b) as a consequence of the increase in the B-O peak area and the decrease in the B-C and B-B peaks. This behavior was observed with MAPP in boronized surfaces exposed to plasmas in NSTX-U, as it also was in other controlled laboratory experiments 6,15,23,24 .…”

Section: Resultssupporting

confidence: 81%

“…The National Spherical Torus Experiment Upgrade (NSTX-U) is a spherical tokamak with carbon-based PFC 12–14 . During the FY2016 experimental campaign, boronization was used as the main PFC conditioning technique in NSTX-U 13,15 . Boron was deposited using a DC glow of He and deuterated Trimethyl boron (d-TMB) 15 .…”

Section: Introductionmentioning

confidence: 99%

“…During the FY2016 experimental campaign, boronization was used as the main PFC conditioning technique in NSTX-U 13,15 . Boron was deposited using a DC glow of He and deuterated Trimethyl boron (d-TMB) 15 . This conditioning yielded boron rich coatings several nanometers thin that enabled plasma performance improvements shortly after their application 6,12 .…”

Section: Introductionmentioning

confidence: 99%

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Effect of deuterium irradiation on graphite boronized in the NSTX-U tokamak

Bedoya

Allain

Domínguez-Gutiérrez

et al. 2019

Sci Rep

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Boronization has been used in the National Spherical Torus-Upgrade (NSTX-U) as first wall conditioning technique. The technique decreased the oxygen impurities in the plasma and the O% on the Plasma Facing Components (PFC) as measured with an in-vacuo probe. Samples were extracted from tiles removed from the tokamak for post-mortem and controlled studies. Ex-vessel low energy and fluence D 2 + and Ar + irradiations were characterized in-situ to elucidate surface evolution of a cored graphite sample with an intrinsic concentration of boron from a tokamak environment. In addition, quadrupole mass spectrometer measurements of emitted D-containing species during irradiation, indicate potential retention of D by the boronized graphite interface and correlated back to the surface chemistry evolution. Classical Molecular Dynamics (CMD) simulations were used to investigate the chemistry of the B-C-O-D system. The results suggest that boron coatings retain oxygen by forming oxidized boron states in the presence of deuterium plasmas and corroborate empirical findings. A four times increase in the O% of the boron coatings was observed following in-situ deuterium exposures, in contrast with a reduction of equal magnitude observed after Ar irradiations. These results illustrate the complex chemistry driven by energetic ions at the edge of tokamaks plasmas on the PFCs.

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Section: Resultssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of deuterium irradiation on graphite boronized in the NSTX-U tokamak

Bedoya

Allain

Domínguez-Gutiérrez

et al. 2019

Sci Rep

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“…An important application of MAPP for the first run campaign of NSTX-U was to characterize the boron deposition from a new deuterated tri-methyl boron (dTMB) boronization system [48]. When new samples were installed, baseline preplasma exposure XPS data were collected, and the samples were then exposed to boronization in NSTX-U followed by Figure 21 shows a summary example of the evolution of the surfaces of one of the ATJ samples from its baseline measurement through several days of plasma exposure.…”

Section: Boronization Assessment Using Materials Analysis Andmentioning

confidence: 99%

Overview of NSTX Upgrade initial results and modelling highlights

Ménard¹,

Allain²,

Battaglia³

et al. 2017

Nucl. Fusion

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The National Spherical Torus Experiment (NSTX) has undergone a major upgrade, and the NSTX Upgrade (NSTX-U) Project was completed in the summer of 2015. NSTX-U first plasma was subsequently achieved, diagnostic and control systems have been commissioned, the H-mode accessed, magnetic error fields identified and mitigated, and the first physics research campaign carried out. During ten run weeks of operation, NSTX-U surpassed NSTX record pulse-durations and toroidal fields (TF), and high-performance ~1 MA H-mode plasmas comparable to the best of NSTX have been sustained near and slightly above the n = 1 no-wall stability limit and with H-mode confinement multiplier H98y,2 above 1. Transport and turbulence studies in L-mode plasmas have identified the coexistence of at least two ion-gyro-scale turbulent micro-instabilities near the same radial location but propagating in opposite (i.e. ion and electron diamagnetic) directions. These modes have the characteristics of ion-temperature gradient and micro-tearing modes, respectively, and the role of these modes in contributing to thermal transport is under active investigation. The new second more tangential neutral beam injection was observed to significantly modify the stability of two types of Alfven eigenmodes. Improvements in offline disruption forecasting were made in the areas of identification of rotating MHD modes and other macroscopic instabilities using the disruption event characterization and forecasting code. Lastly, the materials analysis and particle probe was utilized on NSTX-U for the first time and enabled assessments of the correlation between boronized wall conditions and plasma performance. These and other highlights from the first run campaign of NSTX-U are described.

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“…This is currently one of the most important and still open scientific and technical issues in the design of fusion machines. [1][2][3] Both lithiumization 8,9 and boronization [4][5][6] of carbon based PFCs have been studied in the National Spherical Torus Experiment and its upgraded version (NSTX and NSTX-U) and in related laboratory experiments showing profound effects on both sputtering yields and D retention. Coatings of boron on the carbon surfaces brought a change in surface chemistry during the plasma irradiation which considerably influences the D retention rate 5,6,13 and decreases wall-originated impurities in the plasma 7 by a significant suppression of chemical sputtering.…”

Section: Introductionmentioning

confidence: 99%