Semester of Graduation

Summer 2022

Degree

Master of Science (MS)

Department

Physics and Astronomy

Document Type

Thesis

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) which reduce the neutron flux reaching the detector. We demonstrate through 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. We compare the MPG system to experiments in the literature that use a two-phase-grating-based PGMI with a best-case visibility of around 39% by Pushin et al. 2017. The simulations of the MPG system show improved visibility in comparison to that two-phase-grating-based PGMI. For example, an MPG with a modulation period 120 µm, pitch of 1 µm, and grating heights with a phase modulation of (pi,pi/4), illuminated by a monochromatic beam, produces a visibility of 85% 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 phase sensitivity of 4.5 x 103 for a SDD of 3.5 m and a beam wavelength of 0.44 nm (Kim et al. 2014). For a range of modulation periods, the MPG system provides comparable or greater theoretical maximum phase sensitivity of 4.1 x 103 to 10.0 x 103 for SDD 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 2 phase gratings.

Date

7-11-2022

Committee Chair

Dey, Joyoni

DOI

10.31390/gradschool_theses.5630

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