Speaker
Aleksandr Stepanenko
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1103.pdf
Simulations of divertor plasma turbulence driven by the current-convective
instability under DIII-D-like detached conditions
A.A. Stepanenko1, H.Q. Wang2, S.I. Krasheninnikov1,3
1
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),
Moscow, Kashirskoe highway 31, Russia
2
Oak Ridge Associated Universities, Oak Ridge, TN, USA
3
Department of Mechanical and Aerospace Engineering, University of California, San Diego,
9500 Gilman Drive, La Jolla, California 92093, USA
Investigation of the physical processes determining dynamics of detached divertor plasmas
is highly important for successful prediction of the operational limits of the present-day and
future tokamaks. Recent observations at ASDEX Upgrade (AUG) [1] have demonstrated the
presence of the new state of detachment, called the fluctuating state, characterized by strong
fluctuations of the divertor plasma parameters in the vicinity of the machine X-point, which
vanish once the transition to complete detachment occurs. One of the possible mechanisms
responsible for these oscillations, recently suggested in Ref. 2, can be related to the onset of the
current-convective instability (CCI). The first numerical simulations of plasma dynamics,
driven by the CCI, have demonstrated the plausibility of this mechanism for formation of
saturated turbulence with temporal characteristics akin to those observed at AUG [3].
In this contribution, we employ the model of Ref. 3 to simulate divertor plasma turbulence,
formed by the CCI under the DIII-D-like detached conditions, characterized by the asymmetry
in detachment of the tokamak inner and outer divertors. We demonstrate the frequency and
spatial spectra of turbulence formed by the instability, and their dependence on the plasma and
magnetic field parameters, such as the field line connection length between the target and the
X-point, the magnitude of the electron temperature at the inner strike point, the magnitude of
the electron temperature drop along the magnetic field line inside the inner divertor leg, etc. The
simulation results are also used to reconstruct the fluctuations of the parallel current and
magnetic field at the target near the inner strike point. Where possible, the results of the
simulations are compared with the available experimental data.
References
[1] D. Carralero, G. Birkenmeier, et al., Nucl. Fusion 54, 123005 (2014).
[2] S.I. Krasheninnikov and A.I. Smolyakov, Phys. Plasmas 23, 092505 (2016).
[3] A.A. Stepanenko, S.I. Krasheninnikov, Physics of Plasmas 25, 012305 (2018).
