Physical mechanism behind and access to the I-mode confinement regime in tokamaks. (31st July 2020)

• Record Type: Journal Article
• Authors: Manz, P.; Happel, T.; Stroth, U.; Eich, T.; Silvagni, D.
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 60:Number 9(2020)
• Publication Date: 2020-07-31
• Subjects: tokamak -- I-mode -- turbulence -- drift-wave -- confinement; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/ab9e17
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: The I-mode is an attractive confinement regime for future tokamak based fusion reactors. A model is presented which explains the I-mode regime by the reduction of ITG turbulence near the separatrix at low collisionality, where the separatrix ion temperature can exceed the electron temperature. Drift-Alfvén-turbulence develops, with large and small-scale fluctuations being suppressed by phase randomization and finite-Larmor-radius effects, respectively. The intermediate scales form a broad peak in the frequency spectrum, which features the same properties as the characteristic weakly coherent mode. The model, which is studied by means of gyro-fluid simulations, reproduces a number of other experimental I-mode observations, such as decoupled energy and particle transport, intermittent turbulent bursts with precursors, an operational window widening with magnetic field strength, and the challenges met when detaching the plasma.