  We have developed an improved method of time-resolved x-ray reflectivity
(XRR) using monochromatic synchrotron radiation. Our method utilizes a
polycapillary x-ray optic to create a range of incident angles and an area
detector to collect the specular reflections. By rotating the sample normal out
of the plane of the incident fan, we can separate the surface diffuse scatter
from the reflectivity signal, greatly improving the quality of the XRR spectra
compared to previous implementations. We demonstrate the time-resolved
capabilities of this system, with temporal resolution as low as 10 ms, by
measuring XRR during the annealing of Al/Ni nano-scale multilayers and use this
information to extract the activation energy for interdiffusion in this system.
