| 1. |
- Meyer, H.F., et al.
(author)
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Overview of physics studies on ASDEX Upgrade
- 2019
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Research review (peer-reviewed)abstract
- The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q 95 = 5.5, ) at low density. Higher installed electron cyclotron resonance heating power 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m-1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and E r allow for inter ELM transport analysis confirming that E r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of 'natural' no ELM regimes have been extended. Stable I-modes up to have been characterised using -feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle - measured for the first time - or the cross-phase angle of and fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvénic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.
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| 2. |
- Stroth, U., et al.
(author)
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Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Journal article (peer-reviewed)abstract
- An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts.
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| 3. |
- Fenstermacher, M.E., et al.
(author)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Journal article (peer-reviewed)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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| 4. |
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| 5. |
- Fickert, P., et al.
(author)
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norUrsodeoxycholic acid improves cholestasis in primary sclerosing cholangitis
- 2017
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In: J Hepatol. - 0168-8278. ; 67:3, s. 549-558
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Journal article (peer-reviewed)abstract
- Background & Aim: Primary sclerosing cholangitis (PSC) represents a devastating bile duct disease, currently lacking effective medical therapy. 24-norursodeoxycholic acid (norUDCA) is a side chain-shortened C-23 homologue of UDCA and has shown potent anti-cholestatic, anti-inflammatory and anti-fibrotic properties in a preclinical PSC mouse model. A randomized controlled trial, including 38 centers from 12 European countries, evaluated the safety and efficacy of three doses of oral norUDCA (500 mg/d, 1,000 mg/d or 1,500 mg/d) compared with placebo in patients with PSC. Methods: One hundred sixty-one PSC patients without concomitant UDCA therapy and with elevated serum alkaline phosphatase (ALP) levels were randomized for a 12-week treatment followed by a 4-week follow-up. The primary efficacy endpoint was the mean relative change in ALP levels between baseline and end of treatment visit. Results: norUDCA reduced ALP levels by -12.3%, -17.3%, and -26.0% in the 500, 1,000, and 1,500 mg/d groups (p = 0.029, tively, while a +1.2% increase was observed in the placebo group. Similar dose-dependent results were found for secondary end-points, such as ALT, AST, gamma-GT, or the rate of patients achieving ALP levels < 1.5 x ULN. Serious adverse events occurred in seven patients in the 500 mg/d, five patients in the 1,000 mg/d, two patients in the 1500 mg/d group, and three in the placebo group. There was no difference in reported pruritus between treatment and placebo groups. Conclusions: norUDCA significantly reduced ALP values dose-dependently in all treatment arms. The safety profile of norUDCA was excellent and comparable to placebo. Consequently, these results justify a phase III trial of norUDCA in PSC patients. Lay summary: Effective medical therapy for primary sclerosing cholangitis (PSC) is urgently needed. In this phase II clinical study in PSC patients, a side chain-shortened derivative of ursodeoxycholic acid, norursodeoxycholic acid (norUDCA), significantly reduced serum alkaline phosphatase levels in a dose-dependent manner during a 12-week treatment. Importantly, norUDCA showed a favorable safety profile, which was similar to placebo. The use of norUDCA in PSC patients is promising and will be further evaluated in a phase III clinical study. (C) 2017 European Association for the Study of the Liver. Published by Elsevier B.V.
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| 6. |
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| 7. |
- Bouchal, Johannes M., 1979-, et al.
(author)
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Palynostratigraphical correlation of the excavated Miocene lignite seams of the Yatağan basin (Muğla Province, south-western Turkey)
- 2016
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Conference paper (other academic/artistic)abstract
- The excavated main lignite seams and overlying lacustrine sediments of the opencast mines Eskihisar, Salihpaşalar, and Tınaz, Muğla Province, south-western Turkey were investigated using a high taxonomic resolution palynological approach.The Eskihisar section comprises 47m and 56 samples of which 30 were usable for palynological analysis. The Tınaz section comprises 75 m and 29 samples of which 15 were usable for palynological analysis. Finally, the Salihpaşalar section comprises 25 m and 26 samples of which 16 were usable for palynological analysis. The age of the palynological sections is middle to late Miocene based on radiometric dating and vertebrate fossils. In order to investigate dispersed pollen and spores and their botanical affinities a combined light microscopy and scanning electron microscopy approach was used. The rich palynoflora comprises seven types of algal cysts (Botryococcus, Zygnemataceae), seventeen spore types (Lycopsida, Marsileaceae, Osmundaceae, Pteridaceae, Polypodiaceae), 14 types of gymnosperm pollen (Ephedraceae, Cupressaceae, Pinaceae), five types of monocotyledone pollen (Poaceae, Typhaceae) and ca 90 dicotyledone pollen types (Altingiaceae, Amaranthaceae, Anacardiaceae, Apiaceae, Aquifoliaceae, Asteraceae, Betulaceae, Campanulaceae, Cannabaceae, Caprifoliaceae, Caryophyllaceae, Ericaceae, Eucommiaceae, Euphorbiaceae, Fabaceae, Fagaceae, Geraniaceae, Juglandaceae, Lamiaceae, Linaceae, Lythraceae, Malvaceae, Myricaceae, Oleaceae, Onagraceae, Plumbaginaceae, Polygonaceae, Ranunculaceae, Rosaceae, Salicaceae, Sapindaceae, Sapotaceae, Ulmaceae). The objectives of this investigation were (1) to evaluate whether the three palynological sections were deposited at the same time, and (2) to show regional vegetation differences within a single sedimentary basin. We found three general pollen zones corresponding to different sedimentary settings and palaeoenvironments. The first pollen zone was linked to lignite formation (swamp forest, fern spores, Alnus, Decodon). The second pollen zone reflects lacustrine conditions (Typhaceae) and surrounding hinterland vegetation dominated by Fagaceae. The third pollen zone is dominated by herbaceous taxa, whereas woody taxa are less diverse and less abundant. In general, the three palynological sections are congruent in reflecting distinct pollen zones. However main vegetation types may be represented by different dominating taxa (e. g. Alnus dominace in Eskihisar and Tınaz localities while absent in Salihpaşalar) and rare taxa may differ between localities. Our results demonstrate that in order to achieve a comprehensive understanding of environmental and vegetation conditions in a sedimentary basin, a single palynological section (locality) may not capture the entirety of environmental conditions and changes.
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| 8. |
- Bouchal, Johannes M., 1979-, et al.
(author)
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Some new pollen taxa from the middle Miocene of south western Anatolia
- 2016
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Conference paper (other academic/artistic)abstract
- In an ongoing study, focussing on the plant fossils and palynofloras of the lignite strip mines of the Yatağan basin(Muğla province), a number of pollen taxa, previously not reported from middle Miocene terrestrial sediments of Anatolia were encountered.
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| 9. |
- Bouchal, Johannes M., 1979-, et al.
(author)
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The middle Miocene palynoflora and palaeoenvironments of Eskihisar (Yatağan Basin, southwestern Anatolia): : a combined LM and SEM investigation
- 2016
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In: Botanical journal of the Linnean Society. - : John Wiley & Sons. - 0024-4074 .- 1095-8339. ; 182:1, s. 14-79
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Journal article (peer-reviewed)abstract
- Anatolia was a crossroads for mammal migration during the Miocene due to intermittent land connections between Africa and Anatolia and persisting warm conditions. Here, we investigated a palynological section from middle Miocene sediments of Eskihisar (southwestern Anatolia) in order to establish biogeographic links of the palynoflora and to infer the palaeoenvironment. Four algal palynomorphs, nine spore taxa, eight gymnosperms, three monocots, and 67 dicot pollen types were encountered and investigated using the “single grain method” that combines light microscopy and scanning electron microscopy. Two pollen zones reflect different phases of basin development. Zonal vegetation remained fairly stable across the section and reflects heterogeneous environments including broad-leaved deciduous forest, subtropical forest, and sclerophyllous and semi-evergreen oak forest. Conifers were accessory elements in the broad-leaved deciduous forest communities and replaced these at higher elevations. Some herbaceous taxa (Plumbaginaceae) indicate scattered occurrences of sandy and/or rocky soils. Biogeographic affinities are general Northern Hemispheric, North American, and East Asian as also suggested by the macro fossil record. Only two taxa provide potential biogeographic links with the African flora. This suggests that biome shifts of plant taxa between African subtropical /tropical biomes and Anatolian (western Eurasian) temperate forests and shrublands may have been rare in the middle Miocene.
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| 10. |
- Denk, Thomas, et al.
(author)
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Taxonomy and palaeoecology of two widespread western Eurasian Neogene sclerophyllous oak species: Quercus drymeja Unger and Q. mediterranea Unger
- 2017
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In: Review of Palaeobotany and Palynology. - Amsterdam : Elsevier. - 0034-6667 .- 1879-0615. ; 241, s. 98-128
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Journal article (peer-reviewed)abstract
- Sclerophyllous oaks (genus Quercus) play important roles in Neogene ecosystems of south-western Eurasia. Modern analogues (‘nearest living relatives’) for these oaks have been sought among five of six infrageneric lineages of Quercus, distributed across the entire Northern Hemisphere. A revision of leaf fossils from lower Miocene to Pliocene deposits suggests that morphotypes of the Quercus drymeja complex are very similar to a number of extant Himalayan, East Asian, and Southeast Asian species of Quercus Group Ilex and may indicate subtropical, relatively humid conditions. Quercus mediterranea comprises leaf morphotypes that are encountered in modern Mediterranean species of Quercus Group Ilex, but also in Himalayan and East Asian members of this group indicating fully humid or summer-wet conditions. The fossil taxa Quercus drymeja and Q. mediterranea should be treated as morphotype complexes, which possibly comprised different biological species at different times. Quercus mediterranea, although readily recognizable as a distinct morphotype in early to late Miocene plant assemblages, may in fact represent small leaves of the same plants that constitute the Quercus drymeja complex. Based on the available evidence, the taxa [GG1] forming the Q. drymeja complex and Q. mediterranea thrived in fully humid or summer-wet climates. The onset of the modern vegetational context of Mediterranean sclerophyllous oaks is difficult to trace, but may have been during the latest Pliocene/early Pleistocene.
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