Speaker
Adwiteey Mauriya
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1099.pdf
Implementation and tests of Multiple species collision operator in
Gyrokinetic code GS2
A. Mauriya1 , M. Barnes3 , M. F. F. Nave1,2 and F. Parra3
1 Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa,
P1049-001 Lisbon, Portugal
2 Associação do Instituto Superior Técnico para a Investigação e Desenvolvimento,
P1049-003, Lisbon, Portugal
3 Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford, United Kingdom
Abstract
It is essential to study collisional effects in tokamak plasmas, because it may alter the
momentum redistribution of impurities and main ions. Thus it is required to have a robust
and an accurate collision operator to treat cross-species collisions. Since collision frequency
has Z 4 dependence where Z is the charge, it is essential to consider the impurities. However,
Their densities are significantly less than main ion’ density. Fully linearised gyroaveraged
Fokker-Plank collision operator has been implemented in Gyrokinetic code GS2. Previous
collision operator was gyroaveraged, had pitch angle scattering, diffusion operator and a
modeled field particle operator which conserved the particles, momentum, and energy sat-
isfied the Boltzmann’s H theorem [1]. It was self-collision operator and had finite Larmor
radius effects included in it. It was implicit in time and met all these properties precisely in
the code. Newly implemented collision operator is the extension of previous collision oper-
ator which accounts for cross-species collisions and satisfies the conservation of particles,
momentum, and energy. It also increases the total entropy in time which is an outcome
of Boltzmann’s H theorem. Sugama’s collision operator [2] has been adopted to include
inter-species collisions in GS2. Sugama’s field particles operator is modified to retain the
exact numerical conservation properties. Recursive Sherman Morrison numerical scheme is
implemented to invert the matrix obtained to treat collision operator implicitly. It has been
verified that it satisfies the conservation properties and H Theorem in the GS2. Effects of
impurities along with the main ions has been tested for cyclone base case.
References
[1] M. Barnes, I. G. Abel, W. Dorland, D. R. Ernst, G. W. Hammett, P. Ricci, B. N. Rogers, A. A. Schekochihin,
and T. Tatsuno.
[2] H. Sugama, T.-H. Watanabe, and M. Nunami. Linearized model collision operators for multiple ion species
plasmas and gyrokinetic entropy balance equations. Physics of Plasmas, 16(11):112503, 2009.
