Integrated modeling applications for tokamak experiments with OMFIT. (1st July 2015)

• Record Type: Journal Article
• Authors: Meneghini, O.; Smith, S.P.; Lao, L.L.; Izacard, O.; Ren, Q.; Park, J.M.; Candy, J.; Wang, Z.; Luna, C.J.; Izzo, V.A.; Grierson, B.A.; Snyder, P.B.; Holland, C.; Penna, J.; Lu, G.; Raum, P.; McCubbin, A.; Orlov, D.M.; Belli, E.A.; Ferraro, N.M.; Prater, R.; Osborne, T.H.; Turnbull, A.D.; Staebler, G.M.
• Other Names: other.
• Is Part Of: Nuclear fusion. Volume 55:Number 8(2015:Aug.)
• Publication Date: 2015-07-01
• Subjects: OMFIT -- integrated -- modeling -- DIII-D tokamak; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/55/8/083008
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: One modeling framework for integrated tasks (OMFIT) is a comprehensive integrated modeling framework which has been developed to enable physics codes to interact in complicated workflows, and support scientists at all stages of the modeling cycle. The OMFIT development follows a unique bottom-up approach, where the framework design and capabilities organically evolve to support progressive integration of the components that are required to accomplish physics goals of increasing complexity. OMFIT provides a workflow for easily generating full kinetic equilibrium reconstructions that are constrained by magnetic and motional Stark effect measurements, and kinetic profile information that includes fast-ion pressure modeled by a transport code. It was found that magnetic measurements can be used to quantify the amount of anomalous fast-ion diffusion that is present in DIII-D discharges, and provide an estimate that is consistent with what would be needed for transport simulations to match the measured neutron rates. OMFIT was used to streamline edge-stability analyses, and evaluate the effect of resonant magnetic perturbation (RMP) on the pedestal stability, which have been found to be consistent with the experimental observations. The development of a five-dimensional numerical fluid model for estimating the effects of the interaction between magnetohydrodynamic (MHD) and microturbulence, and its systematic verification against analytic models was also supported by the framework. OMFIT was used for optimizing an innovative high-harmonic fast wave system proposed for DIII-D. For a parallel refractive index, the conditions for strong electron-Landau damping were found to be independent of launched and poloidal angle. OMFIT has been the platform of choice for developing a neural-network based approach to efficiently perform a non-linear multivariate regression of local transport fluxes as a function of local dimensionless parameters. Transport predictions for thousands of DIII-D discharges showed excellent agreement with the power balance calculations across the whole plasma radius and over a broad range of operating regimes. Concerning predictive transport simulations, the framework made possible the design and automation of a workflow that enables self-consistent predictions of kinetic profiles and the plasma equilibrium. It is found that the feedback between the transport fluxes and plasma equilibrium can significantly affect the kinetic profiles predictions. Such a rich set of results provide tangible evidence of how bottom-up approaches can potentially provide a fast track to integrated modeling solutions that are functional, cost-effective, and in sync with the research effort of the community.