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Neutron Interferometry and Optics Facilities

neutron interferometer crystals
Figure 1: A collection of neutron interferometer crystals available at NIST. Each interferometer is made from a perfect-silicon ingot machined to produce diffracting crystal blades that protrude from a common base.

The Neutron Interferometry and Optics Facilities are located at the NIST Center for Neutron Research. They are one of the world's premier facilities for neutron interferometry and related optical measurements. A neutron interferometer splits, then recombines neutron waves. This gives the interferometer its unique ability to experimentally access the phase of neutron waves. Phase measurements are used to study the magnetic, nuclear, and structural properties of materials, as well as tackle fundamental questions in physics. Related, innovative neutron optical techniques for use in condensed matter and materials science research are being developed. The facilities employ several different interferometers (see figure 1) in order to support this wide breadth of applications.

NIOF schematic - full-size
Figure 2: Experiments that require the absolute best phase stability are performed inside a large Hutch pictured here. The Hutch is decoupled from the local environment (especially from vibrations) to preserve the neutron interferometer’s stability over relatively long measurement times (60 seconds).

There are two single crystal neutron interferometry facilities that can operate concurrently. The larger and older of the two is distinguished by the Hutch (see figure 2), a large enclosure to eliminate backgrounds and improve phase stability. To provide neutrons to the inside of the Hutch, neutrons are extracted from a dual-crystal parallel-tracking monochromator system. The sensitivity of the apparatus is greatly enhanced by state-of-the-art thermal, acoustical and vibration isolation systems. To reduce vibration, the Hutch is built on its own foundation, separate from the rest of the building. The position of the inner hutch weighting 40,000 kg is maintained to high precision by a computer-controlled feedback system. The result is a facility with exceptional phase stability and high fringe visibility.

fixed 0.44 nm wavelength neutron beam
Figure 3: A fixed 0.44 nm wavelength neutron beam provides ample space for support equipment to be used in conjecture with a neutron interferometer. This includes cryostat support for the measurement of sample properties through their phase transitions. (People: Prof. Dmitry Pushin and former postdoc Taisiya Mineeva)

Figure 3 shows the second neutron interferometer facility. Neutrons with a fixed 0.44 nm wavelength are reflected into the experimental area. The interferometer is housed in an aluminum box. Although not as phase stable as the Hutch, this fixed wavelength facility allows greater access and more customizable setups. This includes the use of cryostat and other sample environment components to explore sample characteristics not easily measured at other neutron instruments.

Scientific Opportunities/Applications

Quantum mechanics, fundamental physics, and studying quantum materials. Some examples:

  • Neutron phase contrast imaging
  • Measuring the neutron charge radius
  • Understanding crystal structure factors
  • Fifth force searches
  • Phase transition studies
  • Measurement of bound coherent scattering lengths
  • Determining helical / topological material properties
  • Dark energy searches
  • Nonlinear tests of quantum mechanics
  • Testing quantum postulates
  • Decoherence free subspaces
  • Spin-Orbit neutron states
  • Neutron holography
  • Validating advanced crystal fabrication techniques
  • Gravitational quantum interference

FREQUENT AND RECENT COLLABORATORS

Dmitry A. Pushin
dmitry.pushin [at] uwaterloo.ca

Fred E. Wietfeldt
few [at] tulane.edu

Albert Young 
aryoung [at] ncsu.edu

RECENT COLLABORATORING INSTITUTIONS

Indiana University 
Institute of Quantum Computing (Canada)
Nagoya University (Japan)
National Institutes of Health
North Carolina State University
Tulane University
RIKEN (Japan)
University of Maryland
University of North Carolina - Wilmington
University of Waterloo (Canada)

Created October 30, 2015, Updated March 16, 2021