Investigation of ELM [edge localized mode] Dynamics with the Resonant Magnetic Perturbation Effects

Topics covered are: anomalous transport and E x B flow shear effects in the H-mode pedestal; RMP (resonant magnetic perturbation) effects in NSTX discharges; development of a scaling of H-mode pedestal in tokamak plasmas with type I ELMs (edge localized modes); and divertor heat load studies

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Investigation of ELM [edge localized mode] Dynamics with the Resonant Magnetic Perturbation Effects

Topics covered are: anomalous transport and E x B flow shear effects in the H-mode pedestal; RMP (resonant magnetic perturbation) effects in NSTX discharges; development of a scaling of H-mode pedestal in tokamak plasmas with type I ELMs (edge localized modes); and divertor heat load studies

Role of Toroidal Rotation in ITB Formation in Tokamaks

A set of tokamak discharges with internal transport barriers (ITBs) are studied using the TRANSP code in order to investigate the role of toroidal rotation in triggering of ITBs. The toroidal momentum transport is predicted using theory-based Multi-Mode and TGLF anomalous transport models to compute the toroidal rotation profiles and\ua0 the effects of turbulence quenching as a result of associated sheared flows.\ua0 The effect of co- versus counter injected beams on the location and strength of ITBs is studied. Results are presented for existing discharges in order to illustrate the extent to which the Multi-Mode and TGLF models in TRANSP code yield toroidal rotation profiles that are consistent with experimental data. The comparison is quantified by calculating the RMS deviations and Offsets. The self-consistent evolution of the equilibrium is computed using the TEQ module.\ua0 Neoclassical transport is calculated using the Chang-Hinton model. NBI and ICRF heating and current drive are obtained using the NUBEAM and TORIC modules. Supported by US DoE Grant DE-SC0013977 and DE-FG02-92ER54141

Electron Temperature Gradient Driven Transport Model for Tokamak Plasmas

A new model for electron temperature gradient (ETG) modes is developed as a component of the Multi-Mode anomalous transport module [T. Rafiq \textit{et al.,} Phys Plasmas \textbf{20}, 032506 (2013)] to predict a time dependent electron temperature profile in conventional and low aspect ratio tokamaks. This model is based on two-fluid equations that govern the dynamics of low-frequency short- and long-wavelength electromagnetic toroidal ETG driven drift modes. A low collisionality NSTX discharge is used to scan the plasma parameter dependence on the ETG real frequency, growth rate, and electron thermal diffusivity. Electron thermal transport is discovered in the deep core region where modes are more electromagnetic in nature. Several previously reported gyrokinetic trends are reproduced, including the dependencies of density gradients, magnetic shear, $\beta$ and gradient of $\beta$ (\betap), collisionality, safety factor, and toroidicity, where $\beta$ is the ratio of plasma pressure to the magnetic pressure. The electron heat diffusivity associated with the ETG mode is discovered to be on a scale consistent with the experimental diffusivity determined by power balance analysis

Predictive Simulations of ITER Including Neutral Beam Driven Toroidal Rotation

Predictive simulations of ITER [R. Aymar et al., Plasma Phys. Control. Fusion 44, 519 2002] discharges are carried out for the 15 MA high confinement mode (H-mode) 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 (NBI) heated plasmas, for ion cyclotron resonant frequency (ICRF) 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 (1997)], 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 pedesta temperature is 3.5 keV. 2008 American Institute of Physics. [DOI: 10.1063/1.2931037