Generation of X-ray standing waves in a multi-trilayer system with a varying periodicity along its depth is described. Microstructures of a synthetic 15-period Pt/Ni/C multilayer, which has such a varying periodicity, are investigated using X-ray reflectivity (XRR) and X-ray standing wave (XSW) analysis. Microstructural parameters, e. g., thicknesses and electron densities of individual layers, interface roughnesses, varying periodicity along the depth, etc. are precisely determined by the XRR technique. The variation of period is essentially introduced in multilayer fabrication by varying the thickness of the C-layer as a function of depth. The linear increase in C-layer thickness from the bottom of the multilayer towards the surface of the multilayer structure is found by simulating the XRR data with a depth-graded multilayer model. Intensity of the XSW field is computed as a function of depth over the first order Bragg peak. Integrated intensities over the Pt- and the Ni-layers are computed and compared with the measured fluorescence yield from Pt and Ni. Sensitivity for the detection of inter-atomic diffusion across the interfaces in comparison to multi-bilayer systems, such as Pt/C multilayer, is discussed. (C) 2011 Elsevier B. V. All rights reserved.