Speaker
Atsushi Fukuyama
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1072.pdf
Kinetic full wave analysis of electron cyclotron waves in a tokamak
plasma using finite element method
A. Fukuyama1 , S.A. Khan1,2 , H. Igami3 , H. Idei4
1 Department of Nuclear Engineering, Kyoto Univerisity, Kyoto, Japan
2 National Center for Physics, Islamabad, Pakistan
3 National Institute for Fusion Science, Toki, Japan
4 Research Institute for Applied Mathematics, Kyushu University, Kasuga, Japan
Full wave analysis including kinetic effects of plasmas has been extensively employed in
studying ion-cyclotron (IC) heating and lower-hybrid (LH) current drive in tokamak plasmas.
Most of previous analyses of wave propagation and absorption in an inhomogeneous plasma
are based on the response in a uniform plasma and the wave number has an essential role in
describing the plasma-wave interactions. The dielectric tensor in a hot plasma has been usually
expressed as a function of wave number. In order to describe the response of plasma without
wave number, it is appropriate to use an integral form of dielectric tensor derived by integrating
along an unperturbed particle orbit. Maxwell’s equation with the integral form of dielectric ten-
sor is numerically solved as a boundary-value problem by means of the finite element method
(FEM). Numerical analysis with FEM may have higher performance with parallel processing
owing to sparse coefficient matrix. Though the integration is localized in an element in usual
FEM for differential equations, coupling between elements in a localized region occurs in the
FEM for integro-differential equations. In a magnetized plasma, guiding center motion along
an inhomogeneous magnetic field and cyclotron motion perpendicular to the magnetic field are
considered for deriving the dielectric tensor as an integral operator. This scheme was applied to
electron-cyclotron (EC) waves. In the first case of one-dimensional analyses, cyclotron damp-
ing in the presence of magnetic field inhomogeneous along the field line is studied to obtain
the power deposition profile in magnetic beach heating. In the second case, the O-X-B mode
conversion in spherical tokamaks is studied. Mode conversion to the electron Bernstein wave
and strong absorption at the cyclotron resonance are described. The mode-conversion efficiency
is consistent with analytical estimates. The extension to two-dimensional analyses in an equa-
torial plane and a poloidal cross section of tokamak plasmas is also discussed. Computational
performance of integro-differential equation solver using FEM will be also discussed.
