Bremen 2017 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 9: Magnetic Confinement I
P 9.2: Hauptvortrag
Dienstag, 14. März 2017, 09:00–09:30, HS 2010
Physics of heat and momentum transport changes in ohmically confined tokamak plasmas — •Rachael McDermott1, Alexander Lebschy1,2, Ivan Erofeev1, Clemente Angioni1, Emiliano Fable1, and the ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, Garching, Germany — 2Technische Universität München, Garching, Germany
In Ohmically confined tokamak plasmas the energy confinement time is observed to increase linearly with the plasma density up to a critical density above which it saturates. These two regimes, below and above this critical density, are referred to as linear and saturated Ohmic confinement (LOC and SOC) and are ubiquitous to tokamak experiments. In the same general parameter regime, dramatic changes in the core plasma toroidal rotation are also observed, with the rotation actually flipping sign from the co-current to the counter-current direction. These changes in both energy and momentum transport have long been ascribed to changes in the plasma turbulence, which is expected to transition from trapped electron mode (TEM) driven to ion temperature gradient (ITG) driven as the electron density, and hence collisionality, is increased. While recent modelling work does display a gradual TEM-ITG transition throughout the plasma as the density grows, the critical densities of the LOC-SOC transition and the rotation reversals do not correspond to any sudden modification of the global turbulence regime. Rather, the LOC-SOC transition can be related to the increase in ion turbulent transport, which is higher when ITG is dominant.