Speaker
Denis Kuprienko
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1097.pdf
Isotope effect in energy confinement in high density FT-2 tokamak regimes.
D.V. Kouprienko1, A.B. Altukhov1, L.A. Esipov1, A.D. Gurchenko1, E.Z. Gusakov1,
S.I. Lashkul1, S. Leerink2
1
Ioffe Institute, St. Petersburg, Russia
2
Aalto University, Espoo, Finland
The isotope effect in a tokamak confinement resulting, in contradiction to the theory
expectations, in the anomalous transport decrease in numerous experiments with growth of
the hydrogen isotope number remains a long-standing puzzle for the period of 40 years [1].
The novel approach to explanation of this effect, which is favorable for fusion applications, is
based on accounting for the multi-scale turbulence nonlinear interactions. Within this
approach the isotope effect in particle confinement, but not energy, was demonstrated recently
in FT-2 tokamak in hydrogen (H) and deuterium (D) ohmic discharges with modest electron
density ~ (1.5-2.5)×1019 m-3. The higher particle confinement in D-discharges was
correlated in these experiments to a higher excitation level of the GAM in agreement with
results of specially performed global full-f gyrokinetic modeling by ELMFIRE code [2, 3].
In this paper we present the results of further development of energy confinement studies [4]
in FT-2 tokamak at high densities. Special series of Ohmic discharges are performed in H and
D plasmas within the chord averaged density range ~ (5–9)×1019m-3. The energy
confinement time calculations based on measured kinetic profiles demonstrate essential
difference in τE behavior for different gases. Hydrogen plasma follows the LOC to SOC
transition that happens at the densities above ~ 6×1019 m-3. At the same time deuterium
plasma behavior at the highest densities shows further increase of τE with growing density
typical of LOC scenario. In vicinity of tokamak operational density limits lim~ 9×1019 m-3
the energy confinement time in D is twice as high as in H. Confinement improvement in D-
discharge is accompanied by the flattening of the electron density profile in the central region
and its steepening at the edge, followed by essential decrease of radiation losses. The
turbulence evolution with growing plasma density in these regimes is studied both with
reflectometry diagnostics and by the gyrokinetic modeling.
[1] F. Wagner and U. Stroth 1993 Plasma Phys. Control. Fusion 35 1321
[2] A.D. Gurchenko et al. 2016 Plasma Phys. Control. Fusion 58 044002
[3] P. Niskala et al. 2017 Plasma Phys. Control. Fusion 59 044010
[4] D.V. Kouprienko et al. 2017 44th EPS Conference on Plasma Physics, P4.179
