Diffusion coefficients of Fokker-Planck equation for rotating dust grains in a fusion plasma

摘要

In the fusion devices, ions, H atoms, and H-2 molecules collide with dust grains and exert stochastic torques which lead to small variations in angular momentum of the grain. By considering adsorption of the colliding particles, thermal desorption of H atoms and normal H-2 molecules, and desorption of the recombined H-2 molecules from the surface of an oblate spheroidal grain, we obtain diffusion coefficients of the Fokker-Planck equation for the distribution function of fluctuating angular momentum. Torque coefficients corresponding to the recombination mechanism show that the nonspherical dust grains may rotate with a suprathermal angular velocity. (C) 2015 AIP Publishing LLC.