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  • Fast ion stabilization of the ion temperature gradient driven modes in the Joint European Torus hybrid-scenario plasmas : a trigger mechanism for internal transport barrier formation
    Romanelli, F. ...
    Understanding and modelling turbulent transport in thermonuclear fusion plasmas are crucial for designing and optimizing the operational scenarios of future fusion reactors. In this context, plasmas ... exhibiting state transitions,such as the formation of an internal transport barrier (ITB), are particularly interesting since they can shed light on transport physics and offer the opportunity to test different turbulence suppression models. In thispaper, we focus on the modelling of ITB formation in the Joint European Torus (JET) š1đ hybrid-scenario plasmas, where, due to the monotonic safety factor profile, magnetic shear stabilization cannot be invoked to explain the transition. The turbulence suppression mechanism investigated here relies on the increase in the plasma pressure gradient in the presence of a minority of energetic ions. Microstability analysis of the ion temperature gradient drivenmodes (ITG) in the presence of a fast-hydrogen minority shows that energetic ions accelerated by the ion cyclotron resonance heating (ICRH) system (hydrogen, n(H,fast)žn(D,thermal) up to 10%, T-H,T-fastžT-D,T-thermal up to 30) can increase the pressure gradient enough to stabilize the ITG modesdriven by the gradient of the thermal ions (deuterium). Numerical analysis shows that, by increasing the temperature of the energetic ions, electrostatic ITG modes are gradually replaced by nearly electrostatic modes with tearing parity at progressively longer wavelengths. The growth rate of the microtearing modes is found to be lower than that of the ITG modes and comparable to the local E x B-velocity shearing rate. The above mechanism is proposed as a possible trigger for the formation of ITBs in this type of discharges.
    Source: Plasma physics and controlled fusion. - ISSN 0741-3335 (Iss. 4, Vol. 52, 2010, 045007-1-045007-19)
    Type of material - article, component part
    Publish date - 2010
    Language - english
    COBISS.SI-ID - 24740647

source: Plasma physics and controlled fusion. - ISSN 0741-3335 (Iss. 4, Vol. 52, 2010, 045007-1-045007-19)
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