Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions. (20th July 2016)

• Record Type: Journal Article
• Authors: Birkenmeier, G.; Cavedon, M.; Conway, G.D.; Manz, P.; Stroth, U.; Fischer, R.; Fuchert, G.; Happel, T.; Laggner, F.M.; Maraschek, M.; Medvedeva, A.; Nikolaeva, V.; Prisiazhniuk, D.; Pütterich, T.; Ryter, F.; Shao, L.M.; Willensdorfer, M.; Wolfrum, E.; Zohm, H.
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 56:Number 8(2016:Aug.)
• Publication Date: 2016-07-20
• Subjects: magnetic confinement -- pedestal -- high confinement mode -- L-H transition -- limit-cycle oscillations -- edge localized modes; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/56/8/086009
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field B ⋅ θ with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f ∼ ( B t 1 / 2 I p 3 / 2 ) / ( n T ) .