27th IAEA Fusion Energy Conference: summary of sessions EX/C, EX/S and PPC

Campbell, D.J.

doi:10.1088/1741-4326/ab5cee

Cited by 1 publication

(1 citation statement)

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“…The evolution of inter-ELM fluctuations and gradients has been compared between ASDEX Upgrade and DIII-D for similar operating conditions [216,217]. As shown in figure 28, the two machines show very similar evolution of gradients and magnetic fluctuations during an ELM cycle for these discharges (details in [216]).…”

Section: Comparison Of Fluctuations In Asdex Upgrade and Diii-dmentioning

confidence: 99%

Elements of H-mode pedestal structure

Groebner

Saarelma

2023

Plasma Phys. Control. Fusion

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This paper reviews current understanding of key physics elements that control the H-mode pedestal structure, which exists at the boundary of magnetically confined plasmas. The structure of interest is the width, height and gradient of temperature, density and pressure profiles in the pedestal. Emphasis is placed on understanding obtained from combined experimental, theoretical and simulation work and on results observed on multiple machines. Pedestal profiles are determined by the self-consistent interaction of sources, transport and magnetohydrodynamic limits. The heat source is primarily from heat deposited in the core and flowing to the pedestal. This source is computed from modeling of experimental data and is generally well understood. Neutrals at the periphery of the plasma provide the dominant particle source in current machines. This source has a complex spatial structure, is very difficult to measure and is poorly understood. For typical H-mode operation, the achievable pedestal pressure is limited by repetitive, transient magnetohydrodynamic instabilities. First principles models of peeling- ballooning modes are generally able to explain the observed limits. In some regimes, instability occurs below the predicted limits and these remain unexplained. Several mechanisms have been identified as plausible sources of heat transport. These include neoclassical processes for ion heat transport and several turbulent processes, driven by the steep pedestal gradients, as sources of electron and ion heat transport. Reduced models have successfully predicted the pedestal or density at the pedestal top. Firming up understanding of heat and particle transport remains a primary challenge for developing more complete predictive pedestal models.

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Section: Comparison Of Fluctuations In Asdex Upgrade and Diii-dmentioning

confidence: 99%