
Author(s):
M. Chen, Y. Kishimoto, J. Li, D. Saitou

Title:
Theory and simulation of nonlocal thermal smoothing for arbitrary scale length modulation

Date of publication:
Oct. 2008

Key words:
21 IAEA Fusion Energy Conference, IF/P75

Abstract:
We present a theory that describes the nonlocal heat transport and associated thermal smoothing modeling the nonuniform laser illumination by solving the steady state FokkerPlanck (FP) equation. A method that connects higher order ChapmanEnskog expansion for low energy electrons and convolution formula for high energy ones through the selfconsistent determination of the electric field is developed. The theory explicitly expresses the heat flux for arbitrary periodic temperature modulation given by deltaT/T_a=epsilon_T sin(kx) with moderate wave number k lambda_e leq 0.1, where lanbda_e is the electron mean free path. The theory is compared with onedimensional FP simulations by which we investigate the relaxation of sinusoidal temperature perturbations. Reduction of the heat flux from the SpitzerHarm (SH) theory and the hysteresis nature are found to be reproduced. As the wavelength of the modulation becomes shorter, the contribution from high energy electrons to the heat flux is found to increase whereas the total amount of the heat flux is reduced in proportion to (k lambda_e) ^{2}
