| 1. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 2. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 3. |
- Stroth, U., et al.
(författare)
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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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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
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Tidskriftsartikel (refereegranskat)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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| 7. |
- De Ronchi, D, et al.
(författare)
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Occurrence of cognitive impairment and dementia after the age of 60: a population-based study from Northern Italy
- 2005
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Ingår i: Dementia and geriatric cognitive disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 19:2-3, s. 97-105
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Tidskriftsartikel (refereegranskat)abstract
- <i>Objective:</i> To evaluate the age, gender and education distribution of both cognitive impairment and dementia in the whole old age range of the elderly (from 61 years of age and over). <i>Subjects and Methods:</i> The study population consisted of all subjects born in 1930 or before, living in the municipality of Faenza and Granarolo, Italy (n = 7,930). A two-phase study design was implemented, by using the Mini-Mental State Examination and Global Deterioration Scale as screening instruments. The DSM-III-R diagnostic criteria were used for the clinical diagnosis of dementia. A subject was classified as affected by cognitive impairment, no dementia (CIND) if he/she scored 2 or more standard deviations lower than the corrected mean MMSE score. <i>Results:</i> The prevalences of dementia and CIND were 6.5 per 100 (95% CI 5.9–7.0) and 5.1 per 100 (95% CI 4.6–5.6), respectively. The prevalence of CIND was higher than that of dementia in the youngest old groups (61–74 years), both in men and women, whereas the opposite pattern was present among the older old (75+). In the older age groups, dementia prevalence increased exponentially with age, while CIND prevalence was more stable. There was not a substantial gender difference in CIND prevalence in all ages. Only in the subpopulation of higher educated subjects, women had a higher prevalence of both dementia and CIND than men. Lower educated subjects had a higher prevalence of both dementia and CIND. When compared to higher educated persons, subjects without any schooling had odds ratios of 10.9 (CI 7.0–16.7) and 16.7 (CI 11.2–25.0) for dementia and CIND, respectively. <i>Conclusions:</i> Cognitive impairment is very common in the younger old ages (under 70 years of age), whereas dementia becomes predominant after 75 years of age. Both conditions are strongly related to the educational level.
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| 8. |
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| 9. |
- De Ronchi, D, et al.
(författare)
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The combined effect of age, education, and stroke on dementia and cognitive impairment no dementia in the elderly
- 2007
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Ingår i: Dementia and geriatric cognitive disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 24:4, s. 266-273
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Tidskriftsartikel (refereegranskat)abstract
- <i>Background:</i> This study aims to detect the impact of stroke on the occurrence of dementia and cognitive impairment/no dementia (CIND) in different age, sex, and education groups. <i>Methods:</i> Persons with dementia (DSM-III-R) or CIND were identified by a two-phase study design among 7,930 persons from the population-based Faenza Community Aging Study. <i>Results:</i> Subjects with a history of stroke had increased risk of both dementia [risk ratio (RR) = 3.7; 95% confidence interval (CI) = 3.1–4.4] and CIND (RR = 1.7, 95% CI = 1.4–2.2). These associations were stronger in the younger-old (61–74 years) than in the older-old (75+ years), and among higher-educated (4+ years) than lower-educated (0–3 years of schooling) persons. Dementia and CIND prevalence among stroke subjects was similar to the prevalence detected among subjects 10 years older but without a history of stroke. In stroke subjects, dementia prevalence became higher than CIND prevalence 10 years earlier than in non-stroke subjects. A combined effect for dementia due to a history of stroke, increasing age, and decreasing years of schooling was detected. <i>Conclusions:</i> Stroke is a strong risk factor for dementia among younger-old and higher-educated subjects; in the presence of a stroke, dementia onset might occur about 10 years earlier, possibly by accelerating the progression from CIND to dementia.
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