Neutron interferometry using a single modulated phase grating

I Hidrovo; J Dey; H Meyer; D S Hussey; N N Klimov; L G Butler; K Ham; W Newhauser

doi:10.1063/5.0106706

Neutron interferometry using a single modulated phase grating

Rev Sci Instrum. 2023 Apr 1;94(4):045110. doi: 10.1063/5.0106706.

Authors

I Hidrovo¹, J Dey¹, H Meyer¹, D S Hussey², N N Klimov², L G Butler³, K Ham⁴, W Newhauser¹

Affiliations

¹ Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
² NIST Physicsal Measurement Lab, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA.
³ Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
⁴ Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, USA.

PMID: 38081240
DOI: 10.1063/5.0106706

Abstract

Neutron grating interferometry provides information on phase and small-angle scatter in addition to attenuation. Previously, phase grating moiré interferometers (PGMI) with two or three phase gratings have been developed. These phase-grating systems use the moiré far-field technique to avoid the need for high-aspect absorption gratings used in Talbot-Lau interferometers (TLI) that reduce the neutron flux reaching the detector. We first demonstrate, through theory and simulations, a novel phase grating interferometer system for cold neutrons that requires a single modulated phase grating (MPG) for phase-contrast imaging, as opposed to the two or three phase gratings in previously employed PGMI systems. The theory shows the dual modulation of MPG with a large period and a smaller carrier pitch P, resulting in large fringes at the detector. The theory was compared to the full Sommerfeld-Rayleigh diffraction integral simulator. Then, we proceeded to compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with best-case visibility of around 39%. The simulations of the MPG system show improved visibility in comparison to that of the two-phase-grating-based PGMI. An MPG with a modulation period of 300 µm, the pitch of 2 µm, and grating heights with a phase modulation of (π,0, illuminated by a monochromatic beam produces visibility of 94.2% with a comparable source-to-detector distance (SDD) as the two-phase-grating-based PGMI. Phase sensitivity, another important performance metric of the grating interferometer, was compared to values available in the literature, viz. the conventional TLI with the phase sensitivity of 4.5 × 103 for an SDD of 3.5 m and a beam wavelength of 0.44 nm. For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 × 103 to 10.0 × 103 for SDDs of up to 3.5 m. This proposed MPG system appears capable of providing high-performance PGMI that obviates the need for the alignment of two phase gratings.