ELM-free H-mode phase and decoupling of peeling–ballooning stability boundary in the MAST Upgrade tokamak
A linear magnetohydrodynamic (MHD) peeling–ballooning stability analysis of the edge-localized mode (ELM)-free phase of a MAST Upgrade (MAST-U) H-mode plasma is presented. In contrast to other similar discharges, #47018 is found to have a significantly higher and wider pedestal during its ELM-free H-mode phase that lasts for approximately 80 ms; this is made possible by the reduced core MHD mode activity on the q = 2 surface. During this period, there is sustained decoupling of peeling and ballooning branches of the stability boundary on J–α space, opening an access channel to the second stability regime with higher peaks in pedestal current density $$J_{\mathrm{N,ped}}$$ and pressure gradient (α). Such decoupling of the stability boundary has not previously been observed in MAST-U H-modes, and if such a condition can be readily reproduced, it opens a wide range of opportunities for MAST-U to explore low-collisionality peeling-limited pedestal regimes as well as advanced scenarios such as quiescent H-modes that are relevant to future reactors such as STEP and ITER.
- Research Organization:
- General Atomics, San Diego, CA (United States)
- Sponsoring Organization:
- EPSRC; USDOE
- Contributing Organization:
- MAST Upgrade Team
- Grant/Contract Number:
- AC05-00OR22725; SC0018990
- OSTI ID:
- 2475872
- Journal Information:
- Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 12 Vol. 66; ISSN 0741-3335
- Publisher:
- IOP ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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