Effect of Boronization on Ohmic Plasmas in NSTX

Skinner, C.H.; Kugel, H.; Maingi, R.; Wampler, W.R.; Blanchard, W.; Bell, M.G.; Bell, R.E.; LeBlanc, B.; Gates, D.; Kaye, S. M.; LaMarche, P. H.; Menard, J.; Mueller, D.; Na, H.K.; Nishino, Norikazu; Paul, S. F.; Sabbagh, S. A.; Soukhanovskii, V.

doi:10.2172/781481

Cited by 6 publications

(9 citation statements)

References 10 publications

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“…A 25 mm square silicon sample was placed on the vacuum vessel wall at Bay E and analyzed after the initial boronization for thickness and composition. The thickness of the boron on the sample was 100 nm, which was in good agreement with the calculated deposition thickness expected assuming uniform deposition [5]. The B/C stochiometry was 1/3, in good agreement with the ratio of the TMB molecule.…”

Section: Resultssupporting

confidence: 82%

“…TMB boronization using He/TMB GDC was performed 9 times over the last two NSTX operating sessions between September 2000 and July 2001. This resulted in significant improvements in plasma performance [5].…”

Section: * This Work Supported By Doe Contract No De-ac0276ch03073mentioning

confidence: 99%

“…It was found that after 12 discharges, the central radiated power decreased by a factor of 2 during both ohmic and NBI fiducial discharges. Both of these methods of applying boron to the interior of NSTX have produced beneficial effects on plasma performance [5,8].…”

Section: * This Work Supported By Doe Contract No De-ac0276ch03073mentioning

confidence: 99%

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Boronization on NSTX using deuterated trimethylboron

Blanchard

Gernhardt

Kugel

et al.

Proceedings of the 19th IEEE/IPSS Symposium on Fusion Engineering. 19th SOFE (Cat. No.02CH37231)

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Abstract--Boronization on the National Spherical Torus Experiment (NSTX) has proved to be quite beneficial with increases in confinement and density and decreases in impurities observed in the plasma. The boron has been applied to the interior surfaces of NSTX, about every 2 to 3 weeks of plasma operation, by producing a glow discharge in the vacuum vessel using deuterated trimethylboron (TMB) in a 10% mixture with helium. Special NSTX requirements restricted the selection of the candidate boronization method to the use of deuterated boron compounds.Deuterated TMB met these requirements but is a hazardous gas and special care in the execution of the boronization process is required. This paper describes the existing GDC, Gas Injection, and Torus Vacuum Pumping System hardware used for this process, the glow discharge process, and the automated control system that allows for remote operation to maximize both the safety and efficacy of applying the boron coating. The administrative requirements and the detailed procedure for the setup, operation and shutdown of the process are also described.

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Section: Resultssupporting

confidence: 82%

Section: * This Work Supported By Doe Contract No De-ac0276ch03073mentioning

confidence: 99%

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Boronization on NSTX using deuterated trimethylboron

Blanchard

Gernhardt

Kugel

et al.

Proceedings of the 19th IEEE/IPSS Symposium on Fusion Engineering. 19th SOFE (Cat. No.02CH37231)

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“…This system was used for Helium Glow Discharge Cleaning (HeGDC) between plasma discharges and for boronization using a mixture of 5% deuterated-trimethyl boron in 95% helium. Two DC-biased, 60 Hz AC heated filaments near each of these anodes provided preionization both to assist the HeGDC startup between discharges and to provide preionization for the startup of all NSTX plasmas [2][3][4][5][6]. These biased preionization filaments facilitate breakdown of the glow discharge at the actual operating pressure, voltage, and current, thereby greatly simplifying process control [1].…”

Section: Introductionmentioning

confidence: 99%

Design and Performance of NSTX Movable GDC Probe

Kugel

Maingi

Bell

et al. 2007

2007 IEEE 22nd Symposium on Fusion Engineering

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Abstract--The NSTX GDC system has been improved by replacing one of the two fixed anodes with a Movable GDC Probe (MGP) anode that can be inserted 1.2 m to about midway between the inner and outer vessel walls. The purpose was to provide more spatially uniform HeGDC for improving discharge stability and reliability. The MGP has been used reliably between every discharge during the last two NSTX experimental campaigns. It has also been used to apply HeGDC assisted boronization, and more recently, HeGDC assisted lithiumization. The MGP has contributed to improved NSTX performance during long pulse and H-mode discharges, and enabled a faster discharge repetition rate.

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“…NSTX employs a conventional wall conditioning program 10 , which includes center stack resistive bake-out up to 300 deg. C, glow discharge cleaning, and boronization 11,12 .…”

mentioning

confidence: 99%

Characteristics of the First H-mode Discharges in NSTX

Maingi¹,

Bell²,

Bell³

et al. 2001

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We report observations of the first low-to-high (L-H) confinement mode transitions in the National Spherical Torus Experiment (NSTX). The H-mode energy confinement time increased over reference L-mode discharges transiently by 100-300%, as high as 1 50ms. This confinement time is ~ 1.8-2.3 times higher than predicted by a multimachine ELM-free H-mode scaling. This achievement extends the H-mode window of fusion devices down to a record low aspect ratio (R/a) ~ 1.3, challenging both confinement and L-H power thresholds scalings based on conventional aspect ratio tokamaks.

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Effect of Boronization on Ohmic Plasmas in NSTX

Cited by 6 publications

References 10 publications

Boronization on NSTX using deuterated trimethylboron

Boronization on NSTX using deuterated trimethylboron

Design and Performance of NSTX Movable GDC Probe

Characteristics of the First H-mode Discharges in NSTX

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