Influences of substrate thickness on neutron specular reflection

TL;DR

This paper investigates how substrate thickness affects neutron specular reflection measurements, revealing that end-side reflections can significantly influence results, especially near reflectivity minima, and should be considered for accurate data interpretation.

Contribution

It introduces a comprehensive analysis of substrate thickness effects on neutron reflectivity, emphasizing the importance of end-side reflections in experimental interpretation.

Findings

End-side reflections can cause significant deviations in measured reflectivity.

Consideration of substrate thickness is crucial near reflectivity minima.

Neglecting substrate end effects may lead to inaccurate data analysis.

Abstract

In specular reflection experiments the reflected beam from the end side of thick substrates is typically neglected. This is equivalent to assuming the substrates as semi-infinite matter. However, it is known that we should also consider the reflected beam from the end sides. Here we have investigated the effect of this consideration on the average reflectivity in a completely general case. It is shown that in some cases, especially in local minima of reflectivity vs. neutron wave number, this consideration can result in high enough differences such that it should be included in the interpretation of measured neutron specular reflectivity.