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- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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- Carter, J. A., et al.
(författare)
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Ground-based and additional science support for SMILE
- 2024
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Ingår i: Earth and Planetary Physics. - : Science Press. - 2096-3955. ; 8:1, s. 275-298
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Tidskriftsartikel (refereegranskat)abstract
- The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions, and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere. Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission. Here, we describe current community efforts to prepare for SMILE, and the benefits and context various experiments that have explicitly expressed support for SMILE can offer. A dedicated group of international scientists representing many different experiment types and geographical locations, the Ground-based and Additional Science Working Group, is facilitating these efforts. Preparations include constructing an online SMILE Data Fusion Facility, the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar, and the consideration of particular observing strategies and spacecraft conjunctions. We anticipate growing interest and community engagement with the SMILE mission, and we welcome novel ideas and insights from the solar-terrestrial community.
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- Lomanowski, B., et al.
(författare)
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Experimental study on the role of the target electron temperature as a key parameter linking recycling to plasma performance in JET-ILW*
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:6
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Tidskriftsartikel (refereegranskat)abstract
- Changes in global and edge plasma parameters (H (98(y,2)), dimensionless collisionality nu *, core density peaking, separatrix density n (e,sep)) with variations in the D-2 fueling rate and divertor configuration are unified into a single trend when mapped to ⟨T (e,ot)⟩, the spatially averaged spectroscopically derived outer target electron temperature. Dedicated JET with the ITER-like wall (JET-ILW) experiments in combination with an extended JET-ILW database of unseeded low-triangularity H-mode plasmas spanning a wide range of D-2 fueling rates, I (p), B (t) and heating power have demonstrated the importance of ⟨T (e,ot)⟩ as a key physics parameter linking the recycling particle source and detachment with plasma performance. The remarkably robust H (98(y,2)) trend with ⟨T (e,ot)⟩ is connected to a strong inverse correlation between ⟨T (e,ot)⟩, n (e,sep) and nu *, thus directly linking changes in the divertor recycling moderated by ⟨T (e,ot)⟩ with the previously established relationship between nu *, core density peaking and core pressure resulting in a degradation in core plasma performance with decreasing ⟨T (e,ot)⟩ (increasing nu *). A strong inverse correlation between the separatrix to pedestal density ratio, n (e,sep)/n (e,ped), and ⟨T (e,ot)⟩ is also established, with the rise in n (e,sep)/n (e,ped) saturating at ⟨T (e,ot)⟩ > 10 eV. A strong reduction in H (98(y,2)) is observed as ⟨T (e,ot)⟩ is driven from 30 to 10 eV via additional D-2 gas fueling, while the divertor remains attached. Consequently, the pronounced performance degradation in attached divertor conditions has implications for impurity seeding radiative divertor scenarios, in which H (98(y,2)) is already low (similar to 0.7) before impurities are injected into the plasma since moderate gas fueling rates are required to promote high divertor neutral pressure. A favorable pedestal pressure, p (e,ped), dependence on I (p) has also been observed, with an overall increase in p (e,ped) at I (p) = 3.4 MA as ⟨T (e,ot)⟩ is driven down from attached to high-recycling divertor conditions. In contrast, p (e,ped) is reduced with decreasing ⟨T (e,ot)⟩ in the lower I (p) branches. Further work is needed to (i) clarify the potential role of edge opacity on the observed favorable pedestal pressure I (p) scaling; as well as to (ii) project the global and edge plasma performance trends with ⟨T (e,ot)⟩ to reactor-scale devices to improve predictive capability of the coupling between recycling and confined plasma fueling in what are foreseen to be more opaque edge plasma conditions.
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| 8. |
- Lomanowski, B., et al.
(författare)
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Parameter dependencies of the separatrix density in low triangularity L-mode and H-mode JET-ILW plasmas
- 2023
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 63:3, s. 036019-
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Tidskriftsartikel (refereegranskat)abstract
- The midplane electron separatrix density, n(e,sep), in JET-ILW L-mode and H-mode low triangularity deuterium fuelled plasmas exhibits a strong explicit dependence on the averaged outer divertor target electron temperature, n(e,sep) similar to T-e,ot(-1/2). This dependence is reproduced by analytic reversed two point model (rev-2PM), and arises from parallel pressure balance, as well as the ratio of the power and momentum volumetric loss factors, (1 - f(cooling))/(1- f(mom-loss)). Quantifying the influence of the (1 - f(cooling)) and (1 -f(mom-loss)) loss factors on ne,sep has been enabled by measurement estimates of these quantities from L-mode density (fueling) ramps in the outer horizontal, VH
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