Speaker
Petr A. Sdvizhenskii
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1083.pdf
Multiplet effects in radiation losses during discharge quenching
by intense argon injection in ITER
P.A. Sdvizhenskii1, A.B. Kukushkin1,2, M.G. Levashova1, V.E. Zhogolev1, V.M. Leonov1,
V.S. Lisitsa1,2, S.V. Konovalov1
1
National Research Center “Kurchatov Institute”, Moscow, Russia
2
National Research Nuclear University MEPhI, Moscow, Russia
One of conditions of the experimental tokamak reactor ITER’s safe operation is the
possibility of disruption instability mitigation by massive injection of inert gases, in
particular, of argon and neon. While modeling in [1] of Ar and Ne massive gas injection
(MGI) in the ITER 15 MA Q=10 baseline scenario, the MGI is carried out at the quasi-
stationary stage of discharge (flat-top of the current). For modeling of main plasma
parameters, the ASTRA transport code was used, integrated with the ZIMPUR [2] code
which describes the dynamics of charge states, radiation losses and transport of impurities
(radiation losses were simulated in [1] for optically thin coronal plasma).
Here we present the results of estimating the following effects in scenario [1]: (i)
radiation imprisonment, using the Escape Probability model, (ii) deviations from coronal
model, caused by collisional quenching, (iii) fine structure of atomic levels (multiplet
splitting). This consideration is stimulated by the results [3] where the impact of plasma
opacity on the disruption mitigation by the MGI in tokamaks was found (only the first two
effects were considered there). For the most strongly radiating ions at various stages of
discharge quenching (e.g., highly ionized atoms at the initial stage of penetration of impurity
into plasma and weakly ionized atoms at the stage of impurity stirring practically throughout
the entire plasma volume), the optical thickness for the ionic strongest lines appears to be
about 10. However, it has no significant effect on the total radiation power losses of plasma
in the quenching scenario [1]. The most significant effect appears to be the multiplet splitting,
which provides the increase of radiative losses, e.g., for weakly ionized atoms at low
temperatures, because of the contribution from ∆n=0 transitions with lower excitation energy
than that in the model of multiplet-averaged energy levels.
References
[1]. Leonov V.M., Konovalov S.V., Zhogolev V.E., 27th IEEE Symposium on Fusion Engineering (SOFE
2017) Shanghai, China, W.POS.026.
[2]. Leonov V.M., Zhogolev V.E., Plasma Phys. Control. Fusion, v. 47 (2005) 903.
[3]. Lukash V.E., Mineev A.B., Morozov D.Kh. Nucl. Fusion, 2007, v. 47, pp. 1476–1484.
