| 1. |
- 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. |
- Iwaizumi, Masakazu G., et al.
(författare)
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Recent distribution changes affect geographic clines in genetic diversity and structure of Pinus densiflora natural populations in Japan
- 2013
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 304, s. 407-416
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Tidskriftsartikel (refereegranskat)abstract
- Geographic patterns of genetic diversity of widespread tree species with a disturbance-dependent distribution can be influenced by not only past climate change but also disturbance by human activities. This is especially true for species that are dominant mainly in semi-mountainous areas and near human habitation, and also available for forestry. Pinus densiflora is both an economically and ecologically important conifer in semi-mountainous forest landscapes of Japan, and information on its genetic variation is essential for designing programs to manage its natural genetic resources and breeding zones. The geographic pattern of genetic diversity and structure of 62 P. densiflora populations (a total of 1883 trees) across their natural distribution in Japan was examined using eight nuclear microsatellite markers. We found that the allelic richness was somewhat, but significantly, lower in both northern and eastern marginal populations. Analysis of recent bottlenecks detected a significant heterozygosity excess more frequently in the northern and eastern populations. The overall value of the standardized measure of population differentiation was moderate (G'(ST) = 0.122) and similar both to other widespread Japanese tree species and to continental Pinus species. STRUCTURE software analysis revealed a gradual dine in the genetic structure, with three main clusters corresponding to the western, central and northeastern populations; the northeastern cluster showed the highest F value. These results indicated strong genetic drift in the past through rapid population expansion of P. densiflora in northeastern Japan, related to progress in agriculture suggested by anthropological and paleoecological studies. Results obtained on this neutral genetic variation in the nuclear genome should provide fundamental information for designing conservation units and breeding zones and in light of evaluation of its adaptive genetic variation in future studies.
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