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- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
- Fryer, L. J., et al.
(författare)
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3D GUMICS Simulations of Northward IMF Magnetotail Structure
- 2023
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 128:8
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a re-evaluation of the Kullen and Janhunen (2004, https://doi.org/10.5194/angeo-22-951-2004) global northward interplanetary magnetic field (IMF) simulation, using the Grand Unified Magnetosphere–Ionosphere Coupling Simulation version 4 (GUMICS-4), a global MHD model. We investigate the dynamic coupling between northward IMF conditions and the Earth’s magnetotail and compare the results to observation-based mechanisms for the formation of transpolar arcs. The results of this study reveal that under northward IMF conditions (and northward IMF initialization), a large closed field line region forms in the magnetotail, with similarities to transpolar arc structures observed from spacecraft data. This interpretation is supported by the simultaneous increase of closed flux measured in the magnetotail. However, the reconnection configuration differs in several respects from previously theorized magnetotail structures that have been inferred from both observations and simulations results and associated with transpolar arcs. We observe that dawn–dusk lobe regions form as a result of high-latitude reconnection during the initialization stages, which later come into contact as the change in the IMF By component causes the magnetotail to twist. We conclude that in the GUMICS simulation, transpolar arc-like structures are formed as a result of reconnection in the magnetotail, rather than high-latitude reconnection or due to the mapping of the plasma sheet through a twisted magnetotail as interpreted from previous analysis of GUMICS simulations.
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