Neutron detector mobilizes muons for nuclear, quantum material

In a collaboration showing the power of innovation and teamwork, physicists and engineers at the Department of Energy’s Oak Ridge National Laboratory developed a mobile muon detector that promises to enhance monitoring for spent nuclear fuel and help address a critical challenge for quantum computing.

Similar to neutrons, scientists use muons, fundamental subatomic particles that travel at nearly the speed of light, to allow scientists to peer deep inside matter at the atomic scale without damaging samples. However, unlike neutrons, which decay in about 10 minutes, muons decay within a couple of microseconds, posing challenges for using them to better understand the world around us.

The new detector achieves an important step toward ensuring the safety and accountability of nuclear materials and supports the development of advanced nuclear reactors that will help address the challenges of waste management. It also acts as a key step toward developing algorithms and methods to manage errors caused by cosmic radiation in qubits, the basic units of information in quantum computing. The development of the muon detector at ORNL reflects the lab’s strengths in discovery science enabled by multidisciplinary teams and powerful research tools to address national priorities.

“We are thrilled to have brought this vision to life,” said JungHyun Bae, a Wigner Distinguished Staff Fellow leading projects for muon tomography at ORNL. “We have a fantastic community here at ORNL, and the support I’ve received has been invaluable. This project exemplifies the power and innovation of interdisciplinary collaboration at ORNL.”

In late 2024, Bae was recognized in the American Nuclear Society’s 40 Under 40 list.

Based on Spallation Neutron Source neutron detector technology that uses wavelength-shifting fibers, the muon detector will allow scientists to better understand large-scale, dense materials, such as shielded special nuclear materials and spent nuclear fuel. The detector is the outcome of a collaboration between the lab’s Neutron Sciences and Fusion and Fission Energy and Sciences directorates and has been in the making for more than two years. Expected to support an array of applications, including nuclear fuel research, the muon detector will be transferred to its new facility on the ORNL campus for actual measurements this year.

“Collaborative work is essential in scientific research,” said Polad Shikhaliev, senior detector scientist and lead developer for the muon detector. “At ORNL, we have a wealth of expertise, and the willingness to work together is what made this project a success.”

A unique feature of the new detector is its ability to simultaneously measure muon energy and scattering angles, dramatically improving image quality compared to existing muon tomography systems that typically rely on single measurements. This approach provides a more detailed view of a sample, such as a canister containing damaged or hazardous materials.

Likewise, the detector’s features will help scientists understand how cosmic radiation interferes with qubits. Given their inherent fragility, qubits lose their quantum state quickly. Without addressing this limitation, scaling up and realizing practical quantum computers outside laboratory settings will remain elusive. However, the detector will provide the knowledge needed to improve qubit error correction and design tougher qubit hardware.

Looking back to look forward

The project began with a concept Bae developed during his doctoral research that focused on complex computational simulations to validate muon tomography applications. After joining ORNL, Bae encountered major challenges bringing the concept into physical reality. However, on a visit to the American Museum of Science and Energy in Oak Ridge, Tennessee, he discovered the design he needed in a neutron detector on display that was developed by the Neutron Sciences Directorate’s Detectors Group at ORNL led by Yacouba Diawara.

In 2012, that detector made the R&D 100 list. Diawara also edited Neutron Detectors for Scattering Applications, a guide for experts and young scholars that covers the most common neutron detectors used in neutron scattering facilities

Bae contacted Diawara, who immediately recognized how to build the muon tomography system by leaning on his group’s expertise.

“This collaboration is a testament to what can be accomplished when scientists and engineers at ORNL come together with a shared vision,” Diawara said. “The design for the muon detector originated from a neutron detector built specifically for the Spallation Neutron Source more than 10 years ago. The return on investment for that original detector has well exceeded our expectations, generating leading edge technology for discovery science adjacent to and complementary of the power of neutrons.”