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

Description: 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.
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Partner: UNT Libraries Government Documents Department
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First Wall and Operational Diagnostics

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Migration of Artificially Introduced Micron Size Carbon Dust in the DIII-D Divertor

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Dust Measurements in Tokamaks

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Studies of Impurity Assimilation During Massive Argon Gas Injection in DIII-D

Description: Fast shutdown of discharges using massive gas injection (MGI) is a promising technique for reducing tokamak wall damage during disruptions [1]. An outstanding concern, however, is the generation of runaway electrons (RE) during the shutdown. Although RE formation observed during MGI in present-day experiments is quite small (typically <1% of the main plasma current I{sub p} in DIII-D), it is thought that even this small RE current could be amplified to significant levels in reactor-scale tok… more
Date: June 27, 2007
Creator: Hollmann, E.; Jernigan, T.; Parks, P.; Baylor, L.; Boedo, J.; Combs, S. et al.
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Partner: UNT Libraries Government Documents Department
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OEDGE Modeling of {sup 13}C Deposition in the Inner Divertor of DIII-D

Description: 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.
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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

Description: 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.
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Partner: UNT Libraries Government Documents Department
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DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation

Description: Injection of massive quantities of gas is a promising technique for fast shutdown of ITER for the purpose of avoiding divertor and first wall damage from disruptions. Previous experiments using massive gas injection (MGI) to terminate discharges in the DIII-D tokamak have demonstrated rapid shutdown with reduced wall heating and halo currents (relative to natural disruptions) and with very small runaway electron (RE) generation [1]. Figure 1 shows time traces which give an overview of shutdown … more
Date: September 29, 2006
Creator: Hollmann, E.; Jernigan, T.; Antar, G.; Bakhtiari, M.; Boedo, J.; Combs, S. et al.
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Partner: UNT Libraries Government Documents Department
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Modification of Edge Plasma Turbulence by External Magnetic Pertubations

Description: Magnetostatic perturbations applied to the DIII-D plasma using a n=3 coil set have significant impact on the plasma edge, such as edge localized mode (ELM) suppression [1], but also affect the background turbulence levels. Discharges with parameters R=1.75 m, a=0.56 m, B{sub T} {approx} 1.6 T, I{sub p} {approx} 1 MA and n{sub e} {approx} 3 x 10{sup 13} cm{sup -3}-n{sub e} {approx} 7 x 10{sup 13} cm{sup -3} (low, v*{sub e} {approx} 0.1 and moderate, v*{sub e} {approx} 1 electron pedestal collisi… more
Date: June 19, 2006
Creator: Boedo, J.; McKee, G.; Rudakov, D.; Reiser, D.; Evans, T.; Moyer, R. et al.
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Partner: UNT Libraries Government Documents Department
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Scrape-Off Layer Transport and Deposition Studies in DIII-D

Description: 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: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation

Description: Injection of massive quantities of gas is a promising technique for fast shutdown of ITER for the purpose of avoiding divertor and first wall damage from disruptions. Previous experiments using massive gas injection (MGI) to terminate discharges in the DIII-D tokamak have demonstrated rapid shutdown with reduced wall heating and halo currents (relative to natural disruptions) and with very small runaway electron (RE) generation [1]. Figure 1 shows time traces which give an overview of shutdown … more
Date: June 19, 2006
Creator: Hollmann, E.; Jernigan, T.; Antar, G.; Bakhtiari, M.; Boedo, J.; Combs, S. et al.
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Partner: UNT Libraries Government Documents Department
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Particle and Energy Transport in the SOL of DIII-D and NSTX

Description: The far scrape-off layer (SOL) radial transport and plasma-wall contact is mediated by intermittent and ELM-driven transport. Experiments to characterize the intermittent transport and ELMs have been performed in both DIII-D and NSTX under similar conditions. Both intermittent transport and ELMs are comprised of filaments of hot, dense plasma (n{sub e} {approx} 1 x 10{sup 13} cm{sup -3}, T{sub e} {approx} 400 eV) originating at the edge, transport both particles and heat into the SOL by convect… more
Date: October 9, 2006
Creator: Boedo, J.; Maqueda, R.; Rudakov, D.; McKee, G.; Kugel, H.; Maingi, R. et al.
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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

Description: 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.
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Partner: UNT Libraries Government Documents Department
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Far Scrape-Off Layer and Near Wall Plasma Studies in DIII-D

Description: 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.
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Partner: UNT Libraries Government Documents Department
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ELM-Induced Plasma Transport in the DIII-D SOL

Description: High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are composed of fast bursts of hot, dense plasma that travel radially starting at the separatrix at {approx}450 m/s and rotate in the scrape off layer (SOL), convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but decay with radius in the SOL. The temperature … more
Date: December 1, 2004
Creator: Boedo, J.; Rudakov, D.; Hollmann, E.; Moyer, R.; McKee, G.; Burrell, K. et al.
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Partner: UNT Libraries Government Documents Department
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Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D

Description: 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.
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Partner: UNT Libraries Government Documents Department
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