Study of passively stable, fully detached divertor plasma regimes attained in innovative long-legged divertor configurations

Umansky, M.; LaBombard, B.; Brunner, D.; Golfinopoulos, T.; Kuang, Adam; Rensink, M.E.; Terry, J. L.; Wigram, M.; Whyte, D.G.

doi:10.1088/1741-4326/ab46f4

Cited by 11 publications

(12 citation statements)

References 29 publications

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“…The broadening of the heat flux profile relative to the X-point is being investigated. There are likely some effects owing to neutrals and side-wall interactions in the long-leg divertor geometry (Umansky et al 2019). These power loss mechanisms might explain the low target temperatures despite the relatively low impurity fraction.…”

Section: Preliminary Uedge Simulations With 1 % Carbonmentioning

confidence: 99%

Divertor heat flux challenge and mitigation in SPARC

et al. 2020

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Owing to its high magnetic field, high power, and compact size, the SPARC experiment will operate with divertor conditions at or above those expected in reactor-class tokamaks. Power exhaust at this scale remains one of the key challenges for practical fusion energy. Based on empirical scalings, the peak unmitigated divertor parallel heat flux is projected to be greater than 10 GW m−2. This is nearly an order of magnitude higher than has been demonstrated to date. Furthermore, the divertor parallel Edge-Localized Mode (ELM) energy fluence projections (~11–34 MJ m−2) are comparable with those for ITER. However, the relatively short pulse length (~25 s pulse, with a ~10 s flat top) provides the opportunity to consider mitigation schemes unsuited to long-pulse devices including ITER and reactors. The baseline scenario for SPARC employs a ~1 Hz strike point sweep to spread the heat flux over a large divertor target surface area to keep tile surface temperatures within tolerable levels without the use of active divertor cooling systems. In addition, SPARC operation presents a unique opportunity to study divertor heat exhaust mitigation at reactor-level plasma densities and power fluxes. Not only will SPARC test the limits of current experimental scalings and serve for benchmarking theoretical models in reactor regimes, it is also being designed to enable the assessment of long-legged and X-point target advanced divertor magnetic configurations. Experimental results from SPARC will be crucial to reducing risk for a fusion pilot plant divertor design.

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Section: Preliminary Uedge Simulations With 1 % Carbonmentioning

confidence: 99%

Divertor heat flux challenge and mitigation in SPARC

et al. 2020

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“…The region around the X-point is sometimes called the divertor throat. plasma too strongly, if that is a problem, see below) [62,63]whether this would be enough to avoid the need for sweep coils to mitigate the effects of loss of detachment is not yet known.…”

Section: Integration Example 1 Exhaust: Plasma Materials Technology A...mentioning

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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“…Partial detachment is preferable when both handle the power requirements and reduce erosion as it better confines the neutral deuterium within the private region. The greater stability of the detachment front presented in [14,22] of long legged divertors allows for more flexibility in the SXD, making full detachment a more viable option.…”

Section: Detachment Conditionsmentioning

confidence: 99%

“…The focus of this work is the details of the impurity radiation, rather than general differences. Since this work focuses on the impurity radiation, the simulations here include all the impurity charge states (the fixed fraction for impurity species used by Umansky [14] would be insufficient here).…”

Section: Introductionmentioning

confidence: 99%

Increased radiation due to non-coronal effects on DIII-D and MAST-U with varying input power

et al. 2022

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Through SOLPS-ITER simulations of DIII-D and MAST-U, an X-divertor (XD) on DIII-D and a super X-divertor (SXD) on MAST-U were shown to have increased carbon emissivity (PRad/nenI) than corresponding standard divertors (SD) at similar degrees of partial detachment. The reasons behind the increased emissivity in the DIII-D XD and SXD are analyzed using a simple 0D transport model. From the transport model, it is seen that a major cause of the increased emissivity in the XD and SXD over the SDs is a shorter impurity confinement time. An additional cause (for the SXD) is an increase in the ratio of neutral hydrogen to electron density. The input power (Pin) was varied and the XD had a higher emissivity at the higher Pin, unlike the SDs which had the emissivity decrease with increasing Pin. A basic geometrical reason is given to explain both the benefits of the XD over the SD as well as the increase in the XD's emissivity with Pin.

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Study of passively stable, fully detached divertor plasma regimes attained in innovative long-legged divertor configurations

Cited by 11 publications

References 29 publications

Divertor heat flux challenge and mitigation in SPARC

Divertor heat flux challenge and mitigation in SPARC

Towards a fusion power plant: integration of physics and technology

Increased radiation due to non-coronal effects on DIII-D and MAST-U with varying input power

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