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Scrape-Off Layer Features of the QH-Mode

Description: The quiescent high confinement (QH-mode) and quiescent double barrier (QDB) modes in DIII-D have long-duration H-mode confinement without ELMs, possibly an alternative operating mode in future tokamaks for avoiding damage by ELMS. Instead of ELMs, there is an edge harmonic oscillation (EHO), which is a continuous electromagnetic mode with associated density fluctuations. The edge pedestal is similar to ELMing H-mode, but at very low density to daw. We see C{sup +6} ion temperatures of 3-7 keV i… more
Date: May 23, 2002
Creator: Lasnier, C. J.; Burrell, K. H.; deGrassie, J. S.; Leonard, A. W.; Moyer, R. A.; Porter, G. D. et al.
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Partner: UNT Libraries Government Documents Department
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Variation of Particle Control with Changes in Divertor Geometry

Description: Recent experiments on DIII-D point to the importance of two factors in determining how effectively the deuterium particle inventory in a tokamak plasma can be controlled through pumping at the divertor target(s): (1) the divertor magnetic balance, i.e., the degree to which the divertor topology is single-null (SN) or double-null (DN), and (2) the direction of the of Bx{divergent}B ion drift with respect to the X-point(s). Changes in divertor magnetic balance near the DN shape have a much strong… more
Date: October 18, 2004
Creator: Petrie, T. W.; Allen, S. L.; Brooks, N. H.; Fenstermacher, M. E.; Ferron, J. R.; Greenfield, C. M. et al.
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Partner: UNT Libraries Government Documents Department
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Comparison of Carbon and Main Ion Radiation Profiles in Matched Helium and Deuterium Plasmas in JET

Description: This paper examines the radiation profiles and corresponding ionization source profiles of various carbon and main plasma ions in matched helium and deuterium L-mode plasmas in JET. Operation in helium should reduce chemical sputtering of carbon substantially compared with deuterium. The radiation intensities from C{sup 1+}, C{sup 2+} and C{sup 3+} in the helium plasmas showed reduction by factors of 8, 10 and 25 respectively along the inner SOL and divertor leg compared with the deuterium case… more
Date: May 17, 2002
Creator: Fenstermacher, M. E.; Lawson, K. D.; Porter, G. D.; Erents, S. K.; Ingesson, C.; Mathews, G. F. et al.
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Partner: UNT Libraries Government Documents Department
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Modeling The Effect of Drifts on the Edge, Scrape-Off Layer, and Divertor Plasma in DIII-D

Description: Simulations of plasmas with a DIII-D shape indicate plasma drifts are important at power levels near the L- to H-mode plasma transition. In addition to enhancing plasma flows in the divertor region, drifts are found to play a key role in establishing highly sheared radial electric fields in the edge of the confined plasma, for the physics of the high confinement operating mode (H-mode). Measurements of the plasma structure in the vicinity of the X-point of DIII-D indicate the importance of drif… more
Date: June 5, 2001
Creator: Porter, G. D.; Boedo, J. A.; Groebner, R. J.; Carlstrom, T. N.; Rognlien, T. D.; Rensink, M. E. et al.
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Partner: UNT Libraries Government Documents Department
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Investigation of Main-Chamber and Divertor Recycling in DIII-D Using Tangentially Viewing CID Cameras

Description: Measurements of the D{sub {alpha}} emission profiles from the divertor and main chamber region in DIII-D, performed in low-density L-mode, and low and high-density ELMy H-mode plasmas imply that core plasma fueling occurs through the divertor channel. Emission profiles of carbon, combined with UEDGE modeling of the L-mode plasmas, also suggests that chemical sputtering of carbon from the flux surface adjacent to the inner divertor walls, and temperature gradient forces in the scrape-off layer, … more
Date: June 16, 2003
Creator: Groth, M.; Porter, G. D.; Petrie, T. W.; Fenstermacher, M. E. & Brooks, N. H.
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Partner: UNT Libraries Government Documents Department
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Simulations of Boundary Turbulence in Tokamak Experiments

Description: Comparisons between the boundary plasma turbulence observed in the BOUT code and experiments on C-Mod, NSTX, and DIII-D are presented. BOUT is a 3D non-local electromagnetic turbulence simulation code which models boundary-plasma turbulence in a realistic divertor geometry using the modified Braginskii equations for plasma vorticity, density, the electron and ion temperatures and parallel momenta. Many features of the Quasi-Coherent (QC) mode, observed at high densities during enhanced D-alpha … more
Date: October 11, 2002
Creator: Nevins, W. M.; Xu, X. Q.; Carlstrom, T. N.; Cohen, R. H.; Groebner, R.; Jennings, T. et al.
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Partner: UNT Libraries Government Documents Department
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UEDGE and DEGAS modeling of the DIII-D scrape-off layer plasma

Description: This paper presents the results of work to develop benchmarked theoretical models of scrape-off-layer (SOL) characteristics in diverted tokamaks by comparing shot simulations using the UEDGE plasma fluid and DEGAS Monte-Carlo neutral particle transport codes to measurements of the DIII-D SOL plasma. The available experimental data include the radial profiles of electron density and temperature, the ion temperature, the divertor exhaust power, the intensity of H{sub {alpha}} emission, and profil… more
Date: May 1, 1994
Creator: Genstermacher, M. E.; Porter, G. D.; Rensink, M. E.; Rognlien, T. D.; Allen, S. L.; Hill, D. N. et al.
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Partner: UNT Libraries Government Documents Department
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Study of Plasma Detachment in a Simplified 2D Geometry using UEDGE

Description: The location of the ionization front in a generic, detached plasma has been studied in a two-dimensional slab geometry by varying the core plasma density and input heating power. The ratio of the recombination to ionization current and the momentum losses in the computational domain have been used to quantify the degree of detachment. Contours of constant ratio of these parameter in the core plasma density--heating power parameter space show that at high input power higher momentum losses can b… more
Date: August 31, 2001
Creator: Groth, M.; Mahdavi, A. M.; Porter, G. D. & Rognlien, T. D.
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Partner: UNT Libraries Government Documents Department
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Astron Program final report

Description: This report describes important experimental results obtained in the last two years of the Astron Program, an LLL controlled nuclear fusion program which terminated in 1973. Little theoretical work is included, but an extensive bibliography is given. (auth)
Date: August 25, 1975
Creator: Briggs, R. J.; Hester, R. E.; Porter, G. D.; Sherwood, W. A.; Spoerlein, R.; Stallard, B. W. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Developing Models for the DIII-D Boundary Plasma

Description: Development of the comprehensive codes used to study the boundary region of the DIII-D tokamak has been done in parallel with improvement of the diagnostics of this important region of the plasma. These codes have been used to interpret the diagnostic data and assist in design of improved divertor configurations. The development of codes used for analysis on DIII-D is described briefly. Model validation by comparing with the extensive DIII-D boundary region diagnostic data is also discussed.
Date: May 25, 2005
Creator: Porter, G. D.; Rognlien, T. D.; Rensink, M. E.; Stangeby, P. C. & Wolf, N. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Non-Inductive Current Drive Modeling Extending Advanced Tokamak Operation to Steady State

Description: A critical issue for sustaining high performance, negative central shear (NCS) discharges is the ability to maintain current distributions that are maximum off axis. Sustaining such hollow current profiles in steady state requires the use of non-inductively driven current sources. On the DIII-D experiment, a combination of neutral beam current drive (NBCD) and bootstrap current have been used to create transient NCS discharges. The electron cyclotron heating (ECH) and current drive (ECCD) syste… more
Date: June 6, 2000
Creator: Casper, T. A.; Lodestro, L. L.; Pearlstein, L. D.; Porter, G. D.; Murakami, M.; Lao, L. L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Particle Flows in Pumped DIII-D Discharges

Description: The dynamics of particle flows in the DIII-D tokamak for two divertor configurations is considered. Fuel and intrinsic carbon impurity flows are analyzed using experimental data and 2D fluid plasma simulations. The flows in puff and pump experiments done in an open and a closed divertor geometry are described. It is shown that the flow of fuel particles is sensitive to divertor geometry. The pumping efficiency of the DIII-D cryopumps is a factor of 2 higher in a closed geometry than an open. Th… more
Date: May 17, 2000
Creator: Porter, G. D.; Rognlien, T. D.; Rensink, M. E.; Wolf, N. & West, W. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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SCRAPE-OFF LAYER FEATURES OF THE QH-MODE

Description: The quiescent high confinement (QH-mode) and quiescent double barrier (QDB) modes in DIII-D have long-duration H-mode confinement without ELMs, possibly an alternative operating mode in future tokamaks for avoiding damage by ELMs . Instead of ELMs, there is an edge harmonic oscillation (EHO), which is a continuous electromagnetic mode with associated density fluctuations. The edge pedestal is similar to ELMing H-mode, but at very low density to date. We see C{sup +6} ion temperatures of 3-7 keV… more
Date: August 1, 2002
Creator: Lasnier, C. J.; Burrell, K. H.; Degrassie, J. S.; Leonard, A. W.; Moyer, R. A.; Porter, G. D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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UEDGE modeling of the effect of divertor modifications on divertor performance

Description: The DIII'D upper divertor will be modified in late 1999 by installing a continuous dome in the private flux region with an independent pumping capability for the inner strike point. A ''bump'' on the inner cylinder also has been considered to enhance impurity and neutral control. Using the UEDGE code, we have examined the effect of this dome and the ''bump'' on core ionization and core impurity content. For typical parameters, results indicate that the planned divertor modifications enable deta… more
Date: June 23, 1999
Creator: Porter, G. D.; Rensink, M.; Roglien, T. & Wolf, N. S.
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Partner: UNT Libraries Government Documents Department
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Status and Plans for the National Spherical Torus Experimental Research Facility

Description: An overview of the research capabilities and the future plans on the MA-class National Spherical Torus Experiment (NSTX) at Princeton is presented. NSTX research is exploring the scientific benefits of modifying the field line structure from that in more conventional aspect ratio devices, such as the tokamak. The relevant scientific issues pursued on NSTX include energy confinement, MHD stability at high beta, non-inductive sustainment, solenoid-free start-up, and power and particle handling. I… more
Date: July 27, 2005
Creator: Columbia University
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Models and applications of the UEDGE code

Description: The transport of particles and energy from the core of a tokamak to nearby material surfaces is an important problem for understanding present experiments and for designing reactor-grade devices. A number of fluid transport codes have been developed to model the plasma in the edge and scrape-off layer (SOL) regions. This report will focus on recent model improvements and illustrative results from the UEDGE code. Some geometric and mesh considerations are introduced, followed by a general descri… more
Date: September 1, 1996
Creator: Rensink, M. E.; Knoll, D. A.; Porter, G. D.; Rognlien, T. D.; Smith, G. R. & Wising, F.
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Partner: UNT Libraries Government Documents Department
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Scaling of ELM and H-mode pedestal characteristics in ITER shape discharges in the DIII-D tokamak

Description: The authors have shown a correlation between the H-mode pressure pedestal height and the energy confinement enhancement in ITER shape discharges on DIII-D which is consistent with the behavior of H in different ELM classes. The width of the steep gradient region was found to equally well fit the scalings {delta}/R {proportional_to} ({rho}{sub POL}/R){sup 2/3} and {delta}/R {proportional_to} ({beta}{sub POL}{sup PED}/R){sup 1/2}. The normalized pressure gradient {alpha}{sub MHD} was found to be … more
Date: July 1, 1997
Creator: Osborne, T. H.; Groebner, R. J.; Lao, L. L.; Leonard, A. W.; Miller, R. L.; Thomas, D. M. et al.
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Partner: UNT Libraries Government Documents Department
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Plasma flow in the DIII-D divertor

Description: Indications that flows in the divertor can exhibit complex behavior have been obtained from 2-D modeling but so far remain mostly unconfirmed by experiment. An important feature of flow physics is that of flow reversal. Flow reversal has been predicted analytically and it is expected when the ionization source arising from neutral or impurity ionization in the divertor region is large, creating a high pressure zone. Plasma flows arise to equilibrate the pressure. A radiative divertor regime has… more
Date: July 1998
Creator: Boedo, J. A.; Porter, G. D. & Schaffer, M. J.
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Partner: UNT Libraries Government Documents Department
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Scaling and profiles of heat flux during partial detachment in DIII-D

Description: The authors examine the scaling of the peak divertor heat flux and total divertor plate power in partially detached divertor (PDD) discharges in DIII-D, as a function of input power and radiated power. The peak divertor heat flux in the attached plasma increases linearly with input power, but saturates in the detached cases. The total divertor plate power remains linear with input power in both the attached and detached plasmas. This is consistent with the fact that the heat flux peak is reduce… more
Date: August 1998
Creator: Lasnier, C. J.; Hill, D. N.; Allen, S. L.; Fenstermacher, M. E.; Porter, G. D.; Leonard, A. W. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Divertor characterization experiments

Description: Recent DIII-D experiments with enhanced Scrape-off Layer (SOL) diagnostics permit detailed characterization of the SOL and divertor plasma under various operating conditions. We observe two distinct plasma modes: attached and detached divertor plasmas. Detached plasmas are characterized by plate temperatures of only 1 to 2 eV. Simulation of detached plasmas using the UEDGE code indicate that volume recombination and charge exchange play an important role in achieving detachment. When the power … more
Date: June 18, 1996
Creator: Porter, G. D.; Allen, S.; Fenstermacher, M.; Hill, D.; Brown, M.; Jong, R. A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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