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Overview of physics studies on ASDEX Upgrade
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.ORCID iD: 0000-0002-9546-4494
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.ORCID iD: 0000-0001-5603-8559
KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.ORCID iD: 0000-0002-6712-3625
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Number of Authors: 4012019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112014Article in journal (Refereed) Published
Abstract [en]

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, beta(N) <= 2.8) 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 P-sep/R <= 11 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 H-H98(y,H-2) <= 1.1. 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 T-i 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 n/n(GW) <= 0.7 have been characterised using beta-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 T-e and n(e) 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 T-e profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvenic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2019. Vol. 59, no 11, article id 112014
Keywords [en]
nuclear fusion, magnetic confinement, tokamak physics, ITER, DEMO
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-263334DOI: 10.1088/1741-4326/ab18b8ISI: 000490603100002Scopus ID: 2-s2.0-85072124840OAI: oai:DiVA.org:kth-263334DiVA, id: diva2:1368209
Note

QC 20191106

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-06Bibliographically approved

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Frassinetti, LorenzoGarcia Carrasco, AlvaroRatynskaia, Svetlana V.Rubel, MarekThorén, EmilTolias, Panagiotis

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Frassinetti, LorenzoGarcia Carrasco, AlvaroRatynskaia, Svetlana V.Rubel, MarekThorén, EmilTolias, Panagiotis
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