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

TL;DR

This paper introduces a Fisher information-based method for optimizing neutron reflectometry experiments, enabling real-time decision-making and efficient use of beam time by predicting parameter uncertainties and experiment outcomes.

Contribution

The authors develop an analytical Fisher information approach for neutron reflectometry that allows rapid prediction of uncertainties and optimal experimental conditions in real-time.

Findings

Fisher information can be calculated analytically for neutron reflectometry.

The method predicts parameter uncertainties decrease with the square root of measurement time.

The approach effectively guides experimental decisions and saves beam time.

Abstract

An approach based on the Fisher information (FI) is developed to quantify the maximum information gain and optimal experimental design in neutron reflectometry experiments. In these experiments, the FI 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 FI provides a lower bound on parameter estimation uncertainties and 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 FI 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 the investigation of measuring the structural properties of a phospholipid bilayer.