Models for the pedestal temperature at the edge of H-mode tokamak plasmas

Predictive simulations of ITER ͓R. Aymar et al., Plasma Phys. Control. Fusion 44, 519 ͑2002͔͒, discharges are carried out for the 15 MA high confinement mode ͑H-mode͒ scenario using PTRANSP, the predictive version of the TRANSP code. The thermal and toroidal momentum transport equations are evolved using turbulent and neoclassical transport models. A predictive model is used to compute the temperature and width of the H-mode pedestal. The ITER simulations are carried out for neutral beam injection ͑NBI͒ heated plasmas, for ion cyclotron resonant frequency ͑ICRF͒ heated plasmas, and for plasmas heated with a mix of NBI and ICRF. It is shown that neutral beam injection drives toroidal rotation that improves the confinement and fusion power production in ITER. The scaling of fusion power with respect to the input power and to the pedestal temperature is studied. It is observed that, in simulations carried out using the momentum transport diffusivity computed using the GLF23 model ͓R. Waltz et al., Phys. Plasmas 4, 2482 ͑1997͔͒, the fusion power increases with increasing injected beam power and central rotation frequency. It is found that the ITER target fusion power of 500 MW is produced with 20 MW of NBI power when the pedestal temperature is 3.5 keV.

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“…30 The width of the pedestal w ped is determined using a mix of magnetic shear and flow shear and can be expressed as…”

Section: Edge Pedestal Temperature and Widthmentioning

confidence: 99%

Predictive simulations of ITER including neutral beam driven toroidal rotation

et al. 2008

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“…plasma current I P , toroidal field B T , and input power P in ). Pedestal scaling laws are sought in experimental data on existing tokamaks [9] [10] [11] [12], and attempts have been made to extrapolate current pedestal results to ITER [13]. However, without accurate physics-based pedestal models to help explain experimental results, predictions will always lack certainty.…”

Section: Introductionmentioning

confidence: 99%

Advances in measurement and modeling of the high-confinement-mode pedestal on the Alcator C-Mod tokamak

Hughes¹,

LaBombard²,

Mossessian³

et al. 2006

Physics of Plasmas

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Edge transport barrier (ETB) studies on the Alcator C-Mod tokamak [Phys. Plasmas 1, 1511, (1994] investigate pedestal scalings and radial transport of plasma and neutrals.Pedestal profiles show trends with plasma operational parameters such as total current I P .A ballooning-like I 2 P dependence is seen in the pressure gradient, despite calculated stability to ideal ballooning modes. A similar scaling is seen in the near scrape-off-layer for both low-confinement (L-mode) and H-mode discharges, possibly due to electromagnetic fluid drift turbulence setting transport near the separatrix. Neutral density diagnosis allows examination of D 0 fueling in H-modes, yielding profiles of effective particle diffusivity in the ETB, which vary as I P is changed. Edge neutral transport is studied using a 1D kinetic treatment. In both experiment and modeling, the C-Mod density pedestal exhibits a weakly increasing pedestal 1

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“…In the model for pedestal temperature, it is assumed that the edge pressure gradient is limited by high-n ideal MHD ballooning modes and the pedestal width scales like the major radius times the square root of poloidal beta, A = Rdp, [5]. The magnetic shear that is used in the ballooning mode limit is computed one pedestal width from the separatrix and is reduced by the effect of the bootstrap current.…”

mentioning

confidence: 99%

“…The first pedestal model in Ref. [5], which is similar to the one described in this paper, has been used to provide the boundary conditions in simulations of H-mode discharges using the MM95 model in the BALDUR code. It is found that the overall agreement between the modeled profiles and experimental data using the pedestal model previously described is approximately lo%, which is nearly the same as the results obtained when the boundary conditions are prescribed using experimental data.…”

mentioning

confidence: 99%

Burning plasma projections using drift-wave transport models and scalings for the H-mode pedestal

et al. 2003

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The GLF23 and multi-mode core transport models are used along with models for the H-mode pedestal to predict the fusion performance for the International Thermonuclear Experimental Reactor, Fusion Ignition Research Experiment, and IGNITOR tokamak designs. Simulations using combinations of core and pedestal models have also been compared with experimental data for H-mode profiles in DIII-D, JET, and Alcator C-Mod. Power-independent (ballooning mode limit) and power-dependent pedestal scalings lead to very different predictions when used with the core models. Although the two drift-wave transport models reproduce the core profiles in a wide variety of tokamak discharges, they differ in their projections to burning plasma experiments for the same pedestal parameters. Differences in the core transport models in their response to the ion temperature gradient (i.e. their stiffness) and impact of the power dependence of the H-mode pedestal on fusion performance predictions are discussed.

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Models for the pedestal temperature at the edge of H-mode tokamak plasmas

Cited by 84 publications

References 20 publications

Predictive simulations of ITER including neutral beam driven toroidal rotation

Predictive simulations of ITER including neutral beam driven toroidal rotation

Advances in measurement and modeling of the high-confinement-mode pedestal on the Alcator C-Mod tokamak

Burning plasma projections using drift-wave transport models and scalings for the H-mode pedestal

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