1. A method of determining the feasibility of a proposed structure analysis process, said process comprising electron beam excitation of x-rays from a multi-layered structure in order to determine the thicknesses and compositions of the layers, the method comprising: i) generating nominal x-ray data representing the x-ray excitation response of the multi-layered structure according to a first set of one or more process conditions, using nominal structure data comprising compositions and thicknesses for each layer; ii) analysing whether or not it is possible for a structure solver, when given the nominal x-ray data generated according to the first set of process conditions, to calculate output structure data comprising compositions and thicknesses for each layer; and iii) automatically repeating steps (i) and (ii) using different process conditions in place of the first set of process conditions so as to determine under which process conditions, if any, the proposed structure analysis process can be used to determine the thickness and composition of each layer in the multi-layered structure.