Neutron imaging is about contrast—seeing something behind something else or seeing the difference between one side of your sample and the other,” says Hassina Bilheux, an instrument scientist at the US Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL). ORNL reports that construction began last summer on VENUS, a state-of-the-art neutron imaging instrument, at the laboratory’s Spallation Neutron Source (SNS).

Coupled with the SNS, a pulsed accelerator-based neutron source, VENUS will be the only open research facility platform in the United States to provide time-of-flight neutron imaging capabilities to national and international users from government, academia, and industry. Bilheux is a lead developer in the VENUS project.

The scientific capabilities of VENUS will support the research goals of DOE’s Basic Energy Sciences program within the Office of Science as well as other DOE programs or offices such as Biological and Environmental Research, Energy Efficiency & Renewable Energy, and Nuclear Energy.

This new instrument will provide a platform for studying in real time the makeup and performance of a wide range of functional materials under varying environments, offering new state-of-the-art neutron radiographic and tomographic capabilities for materials research.

The ability to directly see the atomic fabric of materials provides pivotal information in accelerating the design and improving the performance of future technologies. Visualizing in real space the behaviors and dynamics of materials requires powerful probes and advanced instrumentation.

VENUS will benefit diverse research areas including the development of energy-related materials (e.g., batteries, nuclear fuels, biofuels); advanced engineering materials (e.g., additively manufactured alloys, aluminum and steel, carbon fibers, concrete, and glass); and studies of archeological and natural materials, providing insights into geological processes, biology, and plant physiology.

Researchers use neutrons to study the structure of matter—from the benchtop to the atomic scale—because neutrons are deeply penetrating, carry no charge, and are nondestructive, making them suitable for studying, for example, biological structures, metal stresses and defects, and magnetic behavior in quantum materials.

In conventional neutron scattering, as neutrons scatter in a material, they reveal information about an atom’s location and behavior. Neutron imaging, on the other hand, measures in transmission—as neutrons pass through a material—to produce neutron radiographs, much like clinical x-rays.

“For example,” Bilheux says, “if you want to see lithium as it’s moving through the battery, you need contrast to isolate the signal coming from lithium ions.”

Building the VENUS beamline at SNS will leverage the facility’s accelerator-based neutron source and provide advanced imaging techniques that complement those currently available at the laboratory’s steady-state neutron source, the High Flux Isotope Reactor. The SNS pulsed-source accelerator enables the time-of-flight technique, which uses time-stamped neutrons that can be adjusted and preselected across a range of energies. The technique provides the tunable contrast necessary for revealing structural information with low-energy neutrons using an approach called Bragg-edge imaging. It also pinpoints specific elements within a sample using high-energy neutrons with resonance imaging to better understand the material’s functional properties and behaviors.

Schematic representation of the VENUS instrument, providing time-of-flight neutron imaging capabilities, at the US Department of Energy’s Oak Ridge National Laboratory (ORNL) in Tennessee. Credit: Jill Hemman, ORNL.

“For example, to distinguish between certain heavy elements such as europium, tantalum, gadolinium, and uranium, one needs higher energy neutrons, which SNS provides,” Bilheux says. “Measuring with VENUS will provide us with three-dimensional maps showing us where a heavy element is located within a sample, and we’ll be able to switch between different heavy elements. That capability will be ... beneficial in optimizing the efficiency of novel nuclear materials, which is a high priority for DOE,” she added. VENUS is on track to be completed in 2022 and is expected to be ready for users by 2023.

“VENUS will enable us to not only gather information about a material’s structure but also how the structure is changing during applied load such as heat or pressure,” Bilheux says. “We’ll be able to do more experiments and get faster results, all without having to use multiple imaging instruments.”

The construction of VENUS is supported by Basic Energy Sciences through funds that were appropriated by the US Congress in FY 2019 for accelerator improvement projects.