Numerical simulations of scattering speckle from phase ordering systems

Abstract

The scattering of coherent X-rays from dynamically evolving systems is currently becoming experimentally feasible. The scattered beam produces a pattern of bright and dark speckles, which fluctuate almost independently in time and can be used to study the dynamics of the system. Here we report large-scale computer simulations of the speckle dynamics for a phase ordering system, using a two-dimensional model quenched through an order--disorder transition into the two-phase regime. The intensity at each wave vector $\mathbf{k}$ is found to be an exponentially distributed random variable. The scaling hypothesis is extended to the two-time correlation function of the scattering intensity at a given wave vector, $Corr(\mathbf{k};t_1,t_2)$. The characteristic decay time difference for the correlation function, $|t_1-t_2{|}_c$, is found to scale as $k|t_1+t_2{|}^{1/2}$.

11 Pages, RevTex, 6 PostScript Figures Accepted to Physica A