Revisiting neutron propagation-based phase contrast imaging and tomography: use of phase retrieval to amplify the effective degree of brilliance

TL;DR

This paper demonstrates that phase retrieval in neutron phase-contrast tomography significantly enhances the signal-to-noise ratio, effectively increasing neutron brilliance by over two orders of magnitude, enabling faster or higher-contrast imaging.

Contribution

It introduces a phase retrieval method for neutron tomography that amplifies the effective neutron brilliance without additional collimation, supported by theoretical expressions and experimental validation.

Findings

Signal-to-noise ratio improved by a factor of 23

Effective neutron brilliance increased over two orders of magnitude

Method allows reduced acquisition time or improved contrast

Abstract

Propagation-based neutron phase-contrast tomography was demonstrated using the ISIS pulsed spallation source. The proof-of-concept tomogram with Paganin-type phase-retrieval filter applied exhibited an effective net boost of $23\pm 1$ in the signal-to-noise ratio as compared to an attenuation-based tomogram, implying a boost in the effective degree of neutron brilliance of over two orders of magnitude. This comparison is for phase retrieval versus conventional absorption with no additional collimation in place. Expressions are provided for the optimal phase-contrast geometry as well as conditions for the validity of the method. The underpinning theory is derived under the assumption of the sample being composed of a single material. The effective boost in brilliance may be employed to give reduced acquisition time, or may instead be used to keep exposure times fixed while improving the measured contrast.