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in creator/contributor: "Brooks, N."

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DiMES Studies of Temperature Dependence of Carbon Erosion and Re-Deposition in the DIII-D Divertor

A strong effect of a moderately elevated surface temperature on net carbon deposition and deuterium co-deposition in the DIII-D divertor was observed under detached conditions. A DiMES sample with a gap 2 mm wide and 18 mm deep was exposed to lower-single-null (LSN) L-mode plasmas first at room temperature, and then at 200 C. At the elevated temperature, deuterium co-deposition in the gap was reduced by an order of magnitude. At the plasma-facing surface of the heated sample net carbon erosion … more

Date: October 2, 2006

Creator: Rudakov, D.; Jacob, W.; Krieger, K.; Litnovsky, A.; Philipps, V.; West, W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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First Wall and Operational Diagnostics

In this chapter we review numerous diagnostics capable of measurements at or near the first wall, many of which contribute information useful for safe operation of a tokamak. There are sections discussing infrared cameras, visible and VUV cameras, pressure gauges and RGAs, Langmuir probes, thermocouples, and erosion and deposition measurements by insertable probes and quartz microbalance. Also discussed are dust measurements by electrostatic detectors, laser scattering, visible and IR cameras, … more

Date: June 19, 2006

Creator: Lasnier, C.; Allen, S.; Boedo, J.; Groth, M.; Brooks, N.; McLean, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Migration of Artificially Introduced Micron Size Carbon Dust in the DIII-D Divertor

Migration of pre-characterized carbon dust in a tokamak environment was studied by introducing about 30 milligrams of dust flakes 5-10 {micro}m in diameter in the lower divertor of DIII-D using the DiMES sample holder. The dust was exposed to high power ELMing Hmode discharges in lower-single-null magnetic configuration with the strike points swept across the divertor floor. When the outer strike point (OSP) passed over the dust holder exposing it to high particle and heat fluxes, part of the d… more

Date: May 15, 2006

Creator: Rudakov, D.; West, W.; Wong, C.; Brooks, N.; Evans, T.; Fenstermacher, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Dust Measurements in Tokamaks

Dust production and accumulation impose safety and operational concerns for ITER. Diagnostics to monitor dust levels in the plasma as well as in-vessel dust inventory are currently being tested in a few tokamaks. Dust accumulation in ITER is likely to occur in hidden areas, e.g. between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In DIII-D tokamak dust diagnostics include Mie scattering from Nd… more

Date: April 23, 2008

Creator: Rudakov, D.; Yu, J.; Boedo, J.; Hollmann, E.; Krasheninnikov, S.; Moyer, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Measurements of carbon and tungsten erosion/deposition in the DIII-D divertor

Net erosion/deposition rates of carbon and tungsten were measured at the outer strike point of the divertor plasma on the floor of the DIII-D tokamak during deuterium H-mode operation at a peak power deposition of about 40 W/cm{sup 2}. For carbon, net erosion rates of up to 4 nm/s were found. For a tungsten film, no appreciable erosion was detected. However, measurements of deposited tungsten on adjacent carbon surfaces indicated a net W erosion rate of 0.06 nm/s.

Date: August 1, 1994

Creator: Bastasz, R.; Wampler, W. R.; Cuthbertson, J. W.; Buchenauer, D. A.; Brooks, N.; Junge, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

OEDGE Modeling of {sup 13}C Deposition in the Inner Divertor of DIII-D

Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power (no beams) L-mode experiment was performed on DIII-D in which {sup 13}CH{sub 4} was puffed into the main vessel through the toroidally-symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the {sup 13}C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. It was found that the… more

Date: December 1, 2004

Creator: Elder, J.; Stangeby, P.; Whyte, D.; Allen, S.; McLean, A.; Boedo, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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13C-Tracer Experiments in DIII-D Preliminary to Thermal Oxidation Experiments to Understand Tritium Recovery in DIII-D, JET, C-Mod, and MAST

Retention of tritium in carbon co-deposits is a serious concern for ITER. Developing a reliable in-situ removal method of the co-deposited tritium would allow the use of carbon plasma-facing components which have proven reliable in high heat flux conditions and compatible with high performance plasmas. Thermal oxidation is a potential solution, capable of reaching even hidden locations. It is necessary to establish the least severe conditions to achieve adequate tritium recovery, minimizing dam… more

Date: June 19, 2006

Creator: Stangeby, P.; Allen, S.; Bekris, N.; Brooks, N.; Christie, K.; Chrobak, C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Scrape-Off Layer Transport and Deposition Studies in DIII-D

Trace {sup 13}CH{sub 4} injection experiments into the main scrape-off layer of low density L-mode and high-density H-mode plasmas have been performed in the DIII-D tokamak [Luxon{_}NF02] to mimic the transport and deposition of carbon arising from a main chamber sputtering source. These experiments indicated entrainment of the injected carbon in plasma flow in the main SOL, and transport toward the inner divertor. Ex-situ surface analysis showed enhanced {sup 13}C surface concentration at the … more

Date: October 27, 2006

Creator: Groth, M.; Allen, S.; Boedo, J.; Brooks, N.; Elder, J.; Fenstermacher, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Plasma boundary experiments on DIII-D tokamak

A survey of the boundary physics research on the DIII-D tokamak and an outline of the DIII-D Advanced Divertor Program (ADP) is presented. We will present results of experiments on impurity control, impurity transport, neutral particle transport, and particle effects on core confinement over a wide range of plasma parameters, I{sub p}{approx lt} 3 MA, {beta}{sub T} {approx lt} 10.7%, P(auxiliary) {approx lt} 20 MW. Based on the understanding gained in these studies, we in collaboration with a n… more

Date: June 1, 1990

Creator: Mahdavi, M. A.; Brooks, N.; Jackson, G. L.; Langhorn, A.; Leikind, B.; Lippmann, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of B-Field Dependent Particle Drifts on ELM Behavior in the DIII-D Boundary Plasma

ELM effects in the DIII-D pedestal and boundary plasmas were measured with multiple fast diagnostics in matched, lower single null, ELMing H-mode discharges with the ion Bx{gradient}B drift toward and away from the divertor. Data show a strong dependence of the delay in inner vs. outer divertor ELM D{sub alpha} emission on drift direction, and a weaker drift dependence of the inner vs. outer delay of the total radiated power, in addition to the strong density dependence seen in previous work [1… more

Date: May 18, 2004

Creator: Fenstermacher, M.; Leonard, A.; Porter, G.; Boedo, J.; Brooks, N.; Groth, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Assessment of the Poloidal Distribution of Core Plasma Fueling and Impurity Sources in DIII-D

Measurements and modeling of the 2D poloidal D{sub {alpha}} intensity distribution in DIII-D low density L-mode and medium density ELMy H-mode plasmas indicate that the core plasma is predominately fueled near the divertor x-point region. The neutral hydrogen and ion carbon emission were measured in the divertor and inner main chamber scrape-off layer (SOL) using a plasma imaging technique, covering 85% of the poloidal cross-section. Typically, the peak emission in the inner main SOL at the tok… more

Date: May 18, 2004

Creator: Groth, M.; Owen, L.; Porter, G.; Brooks, N.; Fenstermacher, M.; Meyer, W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Far Scrape-Off Layer and Near Wall Plasma Studies in DIII-D

Far scrape-off layer (SOL) plasma parameters in DIII-D depend strongly on the discharge density and confinement regime. In L-mode, cross-field transport increases with the average discharge density and elevates the far SOL density, thus increasing plasma-wall contact. Far SOL density near the low field side (LFS) of the main chamber wall also increases with decreasing plasma current and with decreasing outer wall gap. In H-mode, between edge localized modes (ELMs), plasma-wall contact is weaker… more

Date: December 3, 2004

Creator: Rudakov, D.; Boedo, J.; Moyer, R.; Brooks, N.; Doerner, R.; Evans, T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D

Plasma boundary modeling of low density, low confinement plasmas in DIII-D has been benchmarked against a comprehensive set of measurements and indicates that recycling of deuterium ions at the divertor targets, and chemical sputtering at the divertor target plates and walls, can explain the poloidal core fueling profile and core carbon density. Key measurements included the 2-D intensity distribution of deuterium neutral and low-charge state carbon emission in the divertor and around the midpl… more

Date: June 24, 2005

Creator: Groth, M.; Porter, G.; Bray, B.; Brooks, N.; Fenstermacher, M.; Groebner, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department