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in subjects: "Plasma Confinement"  
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The kinetic tandem concept: theory and computer simulations of the potential barriers

Description: The Kinetic Tandem fusion plasma confinement concept is a member of the class of open magnetic confinement systems whose magnetic topology is that of a tube of magnetic flux open at both ends. In open-ended systems the central problem is that of limiting the rate of plasma losses out the ends. In a conventional tandem mirror system end-plugging is accomplished by the generation of positive potential barriers within special short mirror cells located at each end of a long central confinement cel… more
Date: February 11, 1999
Creator: Byers, J A & Post, R F
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Application of RF Power to Plasma Flow Drive in Fusion Confinement

Description: Wave induced flows can produce radially sheared velocity profiles that can in turn stabilize drift wave turbulence and improve plasma confinement. A second-order kinetic theory is developed in one-dimensional slab geometry to treat radio frequency (RF)-driven plasma flows. The Vlasov equation is solved to second order in the RF electric field. Moments of the second-order distribution function give time-averaged expressions for the heating rate, the wave kinetic flux, and the RF force exerted on… more
Date: September 13, 1999
Creator: Batchelor, D. B.; Berry, L. A.; Carter, M. D. & Jaeger, E. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Potential Methods for Improving Pedestal Temperatures and Fusion Performance

Description: The physics of the tokamak edge is very complicated, and the scaling of the H-mode transport barrier pedestal has significant uncertainties. Evidence from the largest tokamaks appears to support a model in which the H-mode pedestal width scales linearly with the poloidal gyroradius and the gradient scales with ideal MHD ballooning limits. However, there appears to be significant variability in the data from different tokamaks, including observations on DIII-D that indicate a regime where the pe… more
Date: October 1, 1999
Creator: Hammett, G. W.; Kotschenreuther, M.; Beer, M. A. & Dorland, W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Investigation of Density Limit Processes in DIII-D

Description: A series of experiments has been conducted in DIII-D to investigate density-limiting processes. The authors have studied divertor detachment and MARFEs on closed field lines and find semi-quantitative agreement with theoretical calculations of onset conditions. They have shown that the critical density for MARFE onset at low edge temperature scales as I{sub p}/a{sup 2}, i.e. similar to Greenwald scaling. They have also shown that the scaling of the critical separatrix density with heating power… more
Date: February 1, 1999
Creator: Maingi, R.; Mahdavi, M. A. & Petrie, T. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A decade of DIII-D research. Final report for the period of work, October 1, 1989--September 30, 1998

Description: During the ten-year DIII-D tokamak operating period of 1989 through 1998, major scientific advances and discoveries were made and facility upgrades and improvements were implemented. Each year, annual reports as well as journal and international conference proceedings document the year-by-year advances (summarized in Section 7). This final contract report, provides a summary of these historical accomplishments. Section 2 encapsulates the 1998 status of DIII-D Fusion Science research. Section 3 … more
Date: March 1, 1999
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Characterization and Modification of Edge-Driven Instabilities in the DIII-D Tokamak

Description: The character of edge localized modes (ELMs) and the height of the edge pressure pedestal in DIII-D tokamak H-mode discharges have been modified by varying the discharge shape (triangularity and squareness) and the safety factor, increasing the edge radiation, and injecting deuterium pellets. Changes in the ELM frequency and amplitude, and the magnitude of the edge pressure gradient, and changes in the calculated extent of the region of access to the ballooning mode second stability regime are … more
Date: July 1, 1999
Creator: Ferron, J. R.; Lao, L. L.; Osborne, T. H.; Strait, E. J.; Turnbull, A. D.; Miller, R. L. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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MHD Instabilities Occurring Near/AT the Transport Barrier, Including Loss of Confinement in H-Modes

Description: In configurations with transport barriers the improved edge and core confinement leads to large pressure gradient and large edge bootstrap current density which often drive magnetohydrodynamic (MHD) instabilities terminating the discharge or reducing the discharge performance. The edge and the core transport barriers deteriorate or are completely lost. In this presentation, recent experimental and theoretical developments concerning MHD instabilities occurring near/at the edge and the core tran… more
Date: September 1, 1999
Creator: Lao, L. L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Theory and models of material erosion and lifetime during plasma instabilities in a tokamak environment.

Description: Surface and structural damage to plasma-facing components (PFCs) due to the frequent loss of plasma confinement remains a serious problem for the tokamak reactor concept. The deposited plasma energy causes significant surface erosion, possible structural failure, and frequent plasma contamination. Surface damage consists of vaporization, spallation, and liquid splatter of metallic materials. Structural damage includes large temperature increases in structural materials and at the interfaces bet… more
Date: November 8, 1999
Creator: Hassanein, A. & Konkashbaev, I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Demonstration of the ITER Power Exhaust Solution Using the Puff and Pump Technique on DIII-D

Description: In future, high power density fusion devices, the need to prevent excessive local deposition of the plasma energy efflux on the first-wall surfaces is a critical design consideration in order to maintain the integrity of such surfaces. This requirement must be met without significant impact on plasma purity or overall plasma confinement. For the International Thermonuclear Experimental Reactor (ITER), these constraints have led to the following design criteria [1] P{sub rad}/(P{sub input} + P{s… more
Date: July 1, 1999
Creator: Wade, M. R.; West, W. P.; Hill, D. N.; Allen, S. L.; Boedo, J. A.; Brooks, N. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Multi-Device Scaling of Neoclassical Tearing Mode Onset with Beta

Description: The islands from tearing modes driven unstable and sustained by helically perturbed neo-classical bootstrap current at high beta often provide the practical limit to long-pulse, high confinement tokamak operation [1,2]. The discharges studied are ELMy H-mode single-null divertor (SND) at q{sub 95} {approx}> 3. Periodic sawteeth with m/n = 1/1 and 2/2 are observed to induce m/n = 3/2 neoclassical tearing modes (NTMs) in the tokamaks Asdex-Upgrade [3], DIII-D [4] and JET [5]; confinement can d… more
Date: July 1, 1999
Creator: La Haye, R. J.; Buttery, R. J.; Guenter, S.; Huysmans, G. T. A. & Wilson, H. R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Science and Technology of the 10-MA Spherical Tori

Description: The Spherical Torus (ST) configuration has recently emerged as an example of confinement concept innovation that enables attractive steps in the development of fusion energy. The scientific potential for the ST has been indicated by recent encouraging results from START,2 CDX-U, and HIT. The scientific principles for the D-fueled ST will soon be tested by NSTX (National Spherical Torus Experiment3) in the U.S. and MAST (Mega-Amp Spherical Tokamak4) in the U.K. at the level of l-2 MA in plasma c… more
Date: November 14, 1999
Creator: Peng, Y-K.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Transitionless Enhanced Confinement and the Role of Radial Electric Field Shear

Description: Evidence for the role of radial electric field shear in enhanced confinement regimes attained without sharp bifurcations or transitions is presented. Temperature scans at constant density, created in the reheat phase following deuterium pellet injection into supershot plasmas in the Tokamak Fusion Test Reactor [J.D. Strachan, et al., Phys. Rev. Lett. 58 (1987) 1004] are simulated using a first-principles transport model. The slow reheat of the ion temperature profile, during which the temperatu… more
Date: October 1, 1999
Creator: Coppi, B.; Ernst, D. R.; Bell, M. G.; Bell, R. E. & Budny, R. V.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Simulation of edge-plasma profiles and turbulence related to L-H transitions in tokamaks

Description: Understanding plasma profile evolution and plasma turbulence are two important aspects of developing a predictive model for edge-plasma in tokamaks and other fusion-related devices. Here they describe results relevant to the L-H transition phenomena observed in tokamaks obtained from two simulations codes which emphasize the two aspects of the problem. UEDGE solves for the two-dimensional (2-D) profiles of a multi-species plasma and neutrals given some anomalous cross-field diffusion coefficien… more
Date: September 21, 1999
Creator: Cohen, R H; Rognlien, T D & Xu, X Q
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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JET Radiative Mantle Experiments in ELMy H-Mode

Description: Radiative mantle experiments were performed on JET ELMy H-mode plasmas. The Septum configuration was used where the X-point is embedded into the top of the Septum. Argon radiated 50% of the input power from the bulk plasma while Z{sub eff} rose from an intrinsic level of 1.5 to about 1.7 due to the injected Argon. The total energy content and global energy confinement time decreased 15% when the impurities were introduced. In contrast, the effective thermal diffusivity in the core confinement r… more
Date: September 28, 1999
Creator: Budny, R.; Coffey, I.; Dumortier, P.; Grisolia, C.; Strachan, J.D. & al, et
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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National Spherical Torus Experiment (NSTX) and Planned Research

Description: The U.S. fusion energy sciences program began in 1996 to increase emphasis on confinement concept innovation. The NSTX [1,2] is being built at PPPL as a national fusion science research facility in response to this emphasis. NSTX is to test fusion science principles of the Spherical Torus (ST) plasmas, which include: (1) High plasma pressure in low magnetic field for high fusion power density, (2) Good energy confinement is a small-size plasma, (3) Nearly fully self-driven (bootstrap) plasma cu… more
Date: November 13, 1999
Creator: Kaye, S.; Neumeyer, C.; Ono, M. & Peng, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Divertor E X B Plasma Convection in DIII-D

Description: Extensive two-dimensional measurements of plasma potential in the DIII-D tokamak divertor region are reported for standard (ion VB{sub T} drift toward divertor X-point) and reversed B{sub T} directions; for low (L) and high (H) confinement modes; and for partially detached divertor mode. The data are consistent with recent computational modeling identifying E x B{sub T} circulation, due to potentials sustained by plasma gradients, as the main cause of divertor plasma sensitivity to B{sub T} dir… more
Date: July 1, 1999
Creator: Boedo, J. A.; Schaffer, M. J.; Maingi, M.; Lasnier, C. J. & Watkins, J. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Advanced Tokamak Scenario Modeling with Off-Axix ECH in DIII-D

Description: Time-dependent simulations with transport coefficients derived from experimentally achieved discharges are used to explore the capability of off-axis electron cyclotron current drive (ECCD) to control hollow current profiles in negative central shear discharges. Assuming these transport coefficients remain unchanged at higher EC power levels, the simulation results show that high confinement, high normalized beta and high bootstrap fraction can be achieved with EC power expected to be available… more
Date: July 1, 1999
Creator: Murakami, M.; Casper, T. A.; Lao, L. L.; St. John, H. E.; Deboo, J. C.; Greenfield, C. M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Effect of Plasma Shape on H-Mode Pedestal Characteristics on DIII-D

Description: The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. The pressure at the top of the H-mode pedestal increases strongly with triangularity primarily due to an increase in the margin by which the edge pressure gradient exceeds the ideal ballooning mode first stability limit. Two models are considered for how the edge may exceed the ballooning mode limit. In one model [1], access to the ballooning mode second stable regime allows the edge pressure … more
Date: December 1, 1999
Creator: Osborne, T. H.; Ferron, J. R.; Groebner, R. J.; Lao, L. L.; Leonard, A. W.; Maingi, R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Comparison of Plasma Performance Between Single-Null and Double-Null Configurations During Elming H-Mode

Description: Tokamak plasma performance generally improves with increased shaping of the plasma cross section, such as higher elongation and higher triangularity. The stronger shaping, especially higher triangularity, leads to changes in the magnetic topology of the divertor. Because there are engineering and divertor physics issues associated with changes in the details of the divertor flux geometry, especially as the configuration transitions from a single-null (SN) divertor to a marginally balanced doubl… more
Date: July 1, 1999
Creator: Petrie, T. W.; Fenstermacher, M. E.; Allen, S. L.; Carlstrom, T. N.; Gohil, P.; Groebner, R. J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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