An optimized upper divertor with divertor-coils to study enhanced divertor configurations in ASDEX Upgrade

Herrmann, A.; Teschke, M.; Zammuto, I.; Faitsch, M.; Kallenbach, A.; Lackner, K.; Lunt, T.; Neu, R.; Rott, M.; Schall, G.; Sieglin, B.; Vorbrugg, S.; Weissgerber, M.; Wischmeier, M.; Zohm, H.

doi:10.1016/j.fusengdes.2017.05.074

Cited by 9 publications

(4 citation statements)

References 5 publications

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“…AUG is currently embarking on a substantial enhancement of the upper divertor co-funded by EUROfusion [133,134]. The new upper divertor (see figure 20(c)) is in its final design stage and will be implemented during a long shutdown starting 2021.…”

Section: Discussionmentioning

confidence: 99%

Overview of physics studies on ASDEX Upgrade

et al. 2019

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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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Section: Discussionmentioning

confidence: 99%

Overview of physics studies on ASDEX Upgrade

et al. 2019

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“…a no-ELM pedestal, and an intense x-point radiating zone), and whether the increased neutral density to deliver the gains are compatible with tritium handling (see next section). There are experiment and theory programmes to address the issues, for example based around MAST-U (Mega Amp Spherical Tokamak Upgrade) [10,11] which was designed to generate a wide range of configurations and divertor leg lengths, including a full super-X configuration (itself an integration challenge) and the advanced divertor programmes on TCV (Tokamak à Configuration Variable) [64], ASDEX Upgrade [65], DIII-D [66] and other devices worldwide. Providing confidence in time for initial decisions on either the reference single null or an alternative (longer leg explored here) will require ingenuity, or ways to allow significant design changes to be made late without adding too much delay (that would need rapid and effective design tools).…”

Section: Uncertaintiesmentioning

confidence: 99%

Towards a fusion power plant: integration of physics and technology

Morris

Akers

Cox

et al. 2022

Plasma Phys. Control. Fusion

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A fusion power plant can only exist with physics and technology acting in synchrony, over space (angstroms to tens of metres) and time (femtoseconds to decades). Recent experience with the European DEMO programme has shown how important it is to start integration early, yet go deep enough to uncover the integration impact, favourable and unfavourable, of the detailed physical and technological characteristics. There are some initially surprising interactions, for example, the fusion power density links the properties of materials in the components to the approaches to waste and remote maintenance in the context of a rigorous safety and environment regime. In this brief tour of a power plant based on a tokamak we outline the major interfaces between plasma physics and technology and engineering considering examples from the European DEMO (exhaust power handling, tritium management and plasma scenarios) with an eye on other concepts. We see how attempting integrated solutions can lead to discoveries and ways to ease interfaces despite the deep coupling of the many aspects of a tokamak plant. A power plant’s plasma, materials and components will be in new parameter spaces with new mechanisms and combinations; the design will therefore be based to a significant extent on sophisticated physics and engineering models making substantial extrapolations. There are however gaps in understanding as well as data – together these are termed “uncertainties”. Early integration in depth therefore represents a conceptual, intellectual and practical challenge, a challenge sharpened by the time pressure imposed by the global need for low carbon energy supplies such as fusion. There is an opportunity (and need) to use emerging transformational advances in computational algorithms and hardware to integrate and advance, despite the “uncertainties” and limited experimental data. We use examples to explore how an integrated approach has the potential to lead to consistent designs that could also be resilient to the residual uncertainties. The paper may stimulate some new thinking as fusion moves to the design of complete power plants alongside an evolving and maturing research programme.

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“…Custom-designed cold panels, such as those in AUG [6,7], or those employing commercial cryocoolers [8], suffer from similar thermal insulation constraints. Commercially available cryopumps, directly installed on existing TCV ports, may cope with the thermal loads, but port availability and shielding from the ambient magnetic fields are a concern.…”

Section: Introductionmentioning

confidence: 99%