Determining the maximum information gain and optimising experimental design in neutron reflectometry using the Fisher information

An approach based on the Fisher information metric (FIM) is developed to quantify the maximum information gain and optimal experimental design in neutron reflectometry experiments. In these experiments, the FIM can be analytically calculated and used to provide sub-second predictions of parameter uncertainties. This approach can be used to influence real-time decisions about measurement angle, measurement time, contrast choice and other experimental conditions based on parameters of interest. The FIM provides a lower bound on parameter estimation errors. These are shown to decrease with the square root of measurement time, providing useful information for the planning and scheduling of experimental work. As the FIM is computationally inexpensive to calculate, it can be computed repeatedly during the course of an experiment, saving costly beam time by signalling that sufficient data has been obtained; or saving experimental datasets by signalling that an experiment needs to continue. The approach's predictions are validated through the introduction of an experiment simulation framework that incorporates instrument specific incident flux profiles, and through investigation of the specific case of measuring the structural properties of a phospholipid bilayer.