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in creator/contributor: "Lasnier, C."

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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

open access

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

open access

Assessment of hot-electron microstability in the initial TMX-U experiments

During the initial TMX-U experiments, we investigated the sloshing-ion and hot-electron distributions. We require these components to ultimately construct a thermal barrier for improved tandem mirror confinement. The plasma parameters we achieved approach values required for thermal barrier operation but have been limited by the power available. This report is concerned with the stability of the hot electron distribution formed. Nonthermal microwave emissions near the electron-cyclotron frequen… more

Date: April 1, 1983

Creator: Casper, T. A.; Chen, Y. J.; Ellis, R.; James, R. & Lasnier, C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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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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Comparison of Plasma Parameters Between QH and ELMing Phases of the Same Discharges

H-mode confinement is observed for many energy confinement times without edge localized modes (ELMs) in QH (quiescent high-confinement)-mode discharges in DIII-D. To find critical differences between ELMing and QH modes we compared electron temperature (T{sub e}), density (n{sub e}), and ion temperature (T{sub i}), in the pedestal and scrape-off layer (SOL) for a group of discharges. We also compared the electron pressures P{sub ped}, and maximum pressure gradients P{sub e,ped,max grad} because… more

Date: May 24, 2004

Creator: Lasnier, C.; West, W.; Burrell, K.; deGrassie, J.; Doyle, E. & Osborne, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Modification of Edge Plasma Turbulence by External Magnetic Pertubations

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.

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

open access

DIII-D Studies of Massive Gas Injection Fast Shutdowns for Disruption Mitigation

Date: June 19, 2006

Creator: Hollmann, E.; Jernigan, T.; Antar, G.; Bakhtiari, M.; Boedo, J.; Combs, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Particle and Energy Transport in the SOL of DIII-D and NSTX

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microstability of TMX-U during initial thermal barrier operation

During the initial thermal barrier experiments on the Tandem Mirror Experiment-Upgrade (TMX-U), we successfully demonstrated the principle of improved axial tandem mirror confinement achieved by establishment of both the thermal barrier and the ion confining potential peak. During this operation, we created both hot (100-keV) mirror-confined electron and hot (8-keV) mirror-confined ion populations in the end cells. In certain parameter ranges, we observed these species to be weakly unstable to … more

Date: March 1, 1984

Creator: Casper, T. A.; Berzins, L. V.; Ellis, R. F.; James, R. A. & Lasnier, C.

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

open access

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