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in creator/contributor: "Hollmann, E."

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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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Edge Localized Mode Dynamics and Transport in the Scrape-Off Layer of the DIII-D Tokamak

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts ({approx}20 to 40 {micro}s long) of hot, dense plasma on a background of less dense, colder plasma ({approx}5 x 10{sup 18} m{sup {+-}3}, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrapeoff layer (SOL), starting at the separatrix at {approx}… more

Date: December 3, 2004

Creator: Boedo, J. A.; Rudakov, D. L.; Hollmann, E.; Gray, D. S.; Burrell, K. H.; Moyer, R. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

open access

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

Studies of Impurity Assimilation During Massive Argon Gas Injection in DIII-D

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.

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

open access

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

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

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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

ELM Particle and Energy Transport in the SOL and Divertor of DIII-D

A271 ELM PARTICLE AND ENERGY TRANSPORT IN THE SOL AND DIVERTOR OF DIII-D. Results from a series of dedicated experiments measuring the effect of particle and energy pulses from Type-I Edge Localized Modes (ELMs) in the DIII-D scrape-off layer (SOL) and divertor are compared with a simple model of ELM propagation in the boundary plasma. The simple model asserts that the propagation of ELM particle and energy perturbations is dominated by ion parallel convection along SOL fields lines and the rec… more

Date: April 1, 2003

Creator: Fenstermacher, M. E.; Leonard, A. W.; Snyder, P. B.; Boedo, J. A.; Colchin, R. J.; Groebner, R. J. 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

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

ELM-Induced Plasma Transport in the DIII-D SOL

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.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Comparison of ELM Pulse Propagation in the DIII-D SOL and Divertors with an Ion Convection Model

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Date: June 23, 2003

Creator: Fenstermacher, M. E.; Porter, G. D.; Leonard, A. W.; Brooks, N. H.; Boedo, J. A.; Colchin, R. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department