Speaker
Alexey Dnestrovskiy
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1080.pdf
Application of modified ASTRA-SPIDER code to simulation of free boundary
equilibrium evolution
A.Yu. Dnestrovskiy 1, A.A. Ivanov 2, S.Yu. Medvedev1,2, V.V. Drozdov3, M.P. Gryaznevich3,
A.R. Polevoi4
1
National Scientific Centre Kurchatov Institure, Moscow, Russian Federation
2
Keldysh Institute of Applied Mathematics, Moscow, Russian Federation
3
Tokamak Energy Ltd, Culham Science Centre, Abingdon, OXON, OX14 3DB, UK
4
ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance, France
In our studies a coupling of the equilibrium solver with a transport code is considered. In such
1.5D codes the evolution of poloidal magnetic flux, density and temperatures of plasma species
are simulated in 1D approximation on the flux grid and with metric coefficients calculated
consistently by 2D equilibrium solver. Our simulations are based on the Automated System for
Transport Analysis (ASTRA) [Pereverzev et al 2002 IPP Report 5/98] and equilibrium solver
SPIDER [Ivanov et al 2005 32nd EPS Conf. on Plasma Physics vol 29C (ECA) P-5.063]. In the
original coupling of the SPIDER to ASTRA7.0 [E Fable et al 2013 Plasma Phys. Control. Fusion
55 124028] the evolution of the poloidal magnetic flux is computed outside the equilibrium
solver. We modified the iteration loop to include the poloidal flux evolution into the internal
iteration loop of the equilibrium solver and circuit equations using the grid adapted to magnetic
fluxes. The comparison has shown that such a modification noticeably improves the convergence
reducing number of iterations in the equilibrium solver with evolving shape and profiles. It also
reduces the total computational time of 1.5D transport evolution, where 2D equilibrium is the
most time-consuming part. Such a modification noticeably improves the convergence for the
cases with strong pressure and current density gradients near the edge for H-mode operation in
tokamak plasmas thus proving to be the most efficient approach to free boundary simulations
with 1.5D transport codes. The efficiency of the proposed scheme further increases for highly
shaped plasmas and fast evolution of plasma parameters.
As an application of the modified 1.5D solver we demonstrate free boundary simulations of
plasma evolution with increasing elongation in the tokamak ST40 [M. Gryaznevich, et al 2017
Fus. Eng. & Des. 123 177-180]. Plasma density, temperature and current density evolution is
simulated with the coupled transport and equilibrium code consistently with the free boundary
plasma shape change. The scenario of current and voltage control in the poloidal field coils is
developed. The dependence of the plasma shape evolution on the scenarios of plasma heating,
fueling and the initial plasma current value is discussed.
