arXiv subjects

Benjamin Heacock

Publications and source records attributed to Benjamin Heacock.

3 recordsLinked to original sources

arXiv2026

Environmental Stabilization of Perfect-Crystal Neutron Interferometry Using a Large Vacuum Chamber with Cryogenic Sample Access

Perfect-crystal neutron interferometry has been a useful tool in measuring nuclear-interactions, probing fundamental physics, and exploring quantum phenomenon. Historically, neutron interferometry experiments have been carried out at room temperature and standard atmospheric pressure. However, neutron interferometry is sensitive to changes in the local environment, especially thermal gradients across the crystal, resulting in phase drifts and systematic uncertainty. A need for measurements performed in different sample environments compound these issues. Fortunately, the use of a vacuum chamber has been shown to be an effective method of environmental isolation for perfect-crystal neutron interferometers. A large volume, highly versatile vacuum chamber has been installed at the Neutron Interferometry and Optics Facility at the NIST Center for Neutron Research to isolate interferometry from local temperature and pressure deviations as well as allowing for the introduction of cryogenically cooled samples. The prospect of incorporating a cryostat within a neutron interferometer opens up new areas of investigation, such as superconductivity. In addition to describing the vacuum chamber, we report on the first measurement of a cryogenic-cooled sample by a neutron interferometer. For this demonstration contrast was measured with a Ni60Cu40 sample between 4 K to 300 K.

physics.ins-det↗

arXiv2021

Pendell\"{o}sung Interferometry Probes the Neutron Charge Radius, Lattice Dynamics, and Fifth Forces

Structure factors describe how incident radiation is scattered from materials such as silicon and germanium and characterize the physical interaction between the material and scattered particles. We use neutron pendell\"{o}sung interferometry to make precision measurements of the (220) and (400) neutron-silicon structure factors, and achieve a factor of four improvement in the (111) structure factor uncertainty. These data provide measurements of the silicon Debye-Waller factor at room temperature and the mean square neutron charge radius $\langle r_n^2 \rangle = -0.1101 \pm 0.0089 \, \mathrm{fm}^2$. Combined with existing measurements of the Debye-Waller factor and charge radius, the measured structure factors also improve constraints on the strength of a Yukawa-modification to gravity by an order of magnitude over the 20 pm to 10 nm length scale range.

nucl-ex↗

arXiv2017

Increased interference fringe visibility from the post fabrication heat treatment of a perfect crystal silicon neutron interferometer

Construction of silicon neutron interferometers requires a perfect crystal silicon ingot (5 cm to 30 cm long) be machined such that Bragg diffracting "blades" protrude from a common base. Leaving the interferometer blades connected to the same base preserves Bragg plane alignment, but if the interferometer contains crystallographic misalignments of greater than about 10 nrad between the blades, interference fringe visibility begins to suffer. Additionally, the parallelism, thickness, and distance between the blades must be machined to micron tolerances. Traditionally, interferometers do not exhibit usable interference fringe visibility until 30 $\mu$m to 60 $\mu$m of machining surface damage is chemically etched away. However, if too much material is removed, the uneven etch rates across the interferometer cause the shape of the crystal blades to be outside of the required tolerances. As a result, the ultimate interference fringe visibility varies widely among neutron interferometers that are created under similar conditions. We find that annealing a previously etched interferometer at $800^\circ \mathrm{C}$ dramatically increased interference fringe visibility from 23 % to 90 %. The Bragg plane misalignments were also measured before and after annealing using neutron rocking curve interference peaks, showing that Bragg plane alignment was improved across the interferometer after annealing. This suggests that current interferometers with low fringe visibility may be salvageable and that annealing may become an important step in the fabrication process of future neutron interferometers, leading to less need for chemical etching and larger, more exotic neutron interferometers.

physics.ins-det↗