Neutron particle passing through tungsten slits, plasma fusion reactor.

Neutron Imaging: How Scientists Are Peering Inside Fusion Reactions

Jordan Keane in Science & Nature September 2025 • 4 min read.

"Unlocking the secrets of fusion energy with advanced neutron imaging techniques at Sandia's Z facility."

Imagine trying to take a picture of something that's not only incredibly small but also exists in the heart of a miniature explosion. That's the challenge scientists face when studying nuclear fusion, the process that powers the sun and holds immense promise for clean energy. To tackle this, researchers at Sandia National Laboratories are using a sophisticated tool called the one-dimensional imager of neutrons, or ODIN, to capture snapshots of these reactions.

At Sandia's Z facility, ODIN helps scientists understand the behavior of neutrons, the neutral particles released during fusion. By analyzing these neutrons, researchers can gain insights into the size, shape, and location of the fusion region, offering crucial information for improving the efficiency of these reactions. This is particularly important for magnetized liner inertial fusion (MagLIF), a technique that uses powerful magnetic fields to compress fuel and trigger fusion.

The challenge? Fusion reactions at the Z facility produce relatively low neutron yields, making it difficult to distinguish neutron signals from background noise like hard X-rays and gamma rays. Additionally, the harsh environment of the Z facility, with its ground shocks and radiation, demands robust and reliable imaging systems. ODIN is designed to overcome these hurdles, providing a clearer picture of what's happening inside these miniature stars.

What is ODIN and How Does It Work?

Neutron particle passing through tungsten slits, plasma fusion reactor.

ODIN is essentially a high-tech camera for neutrons. It consists of a 10-cm block of tungsten with carefully crafted slits, acting as a pinhole to image the neutron source. This design allows scientists to focus on a specific line of sight, achieving a magnification of about 4:1 and a spatial resolution of 500 micrometers. Think of it like using a telephoto lens to zoom in on a distant object, but instead of light, ODIN uses neutrons.

Here's a breakdown of ODIN's key components and their functions:

Tungsten Slit Assembly: The heart of ODIN, featuring rolled edges to define precise slit widths (250, 500, or 750 μm). These slits allow neutrons to pass through while blocking other forms of radiation.
Neutron Detectors: ODIN uses CR-39 plastic detectors, which are insensitive to photons, making them ideal for distinguishing neutrons from X-rays and gamma rays.
Flexible Configurations: ODIN can be configured in different orientations to adjust magnification and sensitivity, allowing researchers to optimize the system for various experimental conditions.
MCNP Modeling: Scientists use sophisticated modeling software (MCNP6.1) to simulate neutron behavior and predict ODIN's response under different conditions, ensuring accurate data interpretation.

The goal is to determine the size, shape, and location of the region producing neutrons during fusion. Challenges include telling apart neutrons from hard x-rays and gammas while maintaining adequate signal-to-noise with the imager to various imaging detectors. Modeling efforts were conducted with MCNP6.1 to determine neutron response functions for varying configurations in a clean DD neutron environment.

The Future of Fusion is Now

The development and refinement of ODIN represent a significant step forward in our ability to study and understand nuclear fusion. By providing detailed images of neutron production, ODIN helps scientists optimize fusion reactions, bringing us closer to a future powered by clean, sustainable energy. As modeling techniques improve and experimental data refines our understanding, neutron imaging will continue to play a vital role in unlocking the full potential of fusion.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1063/1.5039366, Alternate LINK

Title: Modeling The One-Dimensional Imager Of Neutrons (Odin) For Neutron Response Functions At The Sandia Z Facility

Subject: Instrumentation

Journal: Review of Scientific Instruments

Publisher: AIP Publishing

Authors: J. D. Vaughan, C. L. Ruiz, D. Fittinghoff, M. J. May, D. J. Ampleford, G. W. Cooper, G. A. Chandler, K. Hahn, J. D. Styron, B. R. Mcwatters, J. Torres, A. J. Maurer, B. Jones

Published: 2018-10-01

Everything You Need To Know

What is ODIN and what role does it play in studying nuclear fusion at Sandia's Z facility?

ODIN, the one-dimensional imager of neutrons, is a specialized instrument used at Sandia's Z facility to capture images of neutron production during nuclear fusion reactions. By analyzing the neutrons, scientists can determine the size, shape, and location of the fusion region. This information is crucial for understanding and optimizing techniques like magnetized liner inertial fusion (MagLIF), which aims to compress fuel using powerful magnetic fields to initiate fusion.

How does ODIN differentiate between neutrons and other types of radiation produced during fusion experiments at the Z facility, such as hard X-rays and gamma rays?

ODIN uses several techniques to distinguish neutrons from other types of radiation. First, it utilizes a tungsten slit assembly to filter out unwanted radiation. Second, ODIN employs CR-39 plastic detectors, which are insensitive to photons. This makes them ideal for specifically detecting neutrons while ignoring X-rays and gamma rays. By combining these methods, ODIN can provide a clearer signal of neutron production, even in the harsh radiation environment of the Z facility.

What are the key components of ODIN, and how do they contribute to its function as a 'high-tech camera for neutrons'?

ODIN comprises several key components working in concert. The tungsten slit assembly, with its carefully crafted slits, acts as a pinhole to image the neutron source. CR-39 plastic detectors are used because they are insensitive to photons, which helps in distinguishing neutrons from X-rays and gamma rays. Its flexible configurations allow adjustments to magnification and sensitivity. Additionally, MCNP6.1 modeling software is used to simulate neutron behavior and predict ODIN's response under different conditions. Together, these components enable ODIN to capture detailed images of neutron production during fusion reactions.

What challenges do scientists face when using neutron imaging to study fusion reactions at facilities like Sandia's Z, and how does ODIN address these?

One significant challenge is the relatively low neutron yields produced during fusion reactions, which makes it difficult to distinguish neutron signals from background noise like hard X-rays and gamma rays. Additionally, the Z facility's harsh environment, with its ground shocks and radiation, requires robust and reliable imaging systems. ODIN addresses these challenges through its specialized design, which includes the use of a tungsten slit assembly and CR-39 plastic detectors to filter out unwanted radiation and detect neutrons. MCNP6.1 modeling helps researchers predict ODIN's response under varying experimental conditions.

What implications does the advancement of neutron imaging techniques, particularly the development and refinement of ODIN, have for the future of fusion energy research and the pursuit of cleaner energy sources?

The advancement of neutron imaging techniques, exemplified by ODIN, represents a significant step toward realizing the potential of fusion energy. By providing detailed images of neutron production, ODIN enables scientists to optimize fusion reactions and improve the efficiency of techniques such as MagLIF. As modeling techniques like MCNP6.1 improve and experimental data refines our understanding, neutron imaging will play a crucial role in unlocking the full potential of fusion as a clean, sustainable energy source. The improved understanding of neutron behavior and fusion dynamics will allow for more efficient and controlled fusion reactions, paving the way for practical fusion power plants.