Spallation Neutron Source achieves another major milestone

The Proton Power Upgrade, or PPU, project at Oak Ridge National Laboratory's Spallation Neutron Source, or SNS, has achieved its final key performance parameter of 1,250 hours of neutron production at 1.7 megawatts of proton beam power on a newly developed target. All project key performance parameters have now been demonstrated, and the team is preparing for the Department of Energy project completion review, scheduled for mid-January 2025.

By a process called spallation, SNS produces neutrons using an accelerator-based system that delivers short (microsecond) proton pulses to a steel target filled with liquid mercury. The neutrons are then directed toward state-of-the-art research instruments that provide a variety of capabilities to researchers across a broad range of disciplines, such as physics, chemistry, biology and materials science.

Neutron scattering is an essential technique for advancing materials research that supports the U.S. economy and offers solutions to challenges in energy, security and transportation. Neutrons provide information that cannot be obtained using any other research method.

SNS and a second, complementary neutron source at ORNL, the High Flux Isotope Reactor, or HFIR, are available to researchers around the world as a DOE Office of Science user facilities. Submitted research proposals are reviewed by independent scientists from the neutron scattering community to ensure the most promising projects are chosen.

The PPU project has already developed a 2.0-megawatt-capable mercury target for the First Target Station and constructed a tunnel extension to facilitate future connection to a planned third complementary neutron source, the Second Target Station, or STS. Eventually the SNS proton beam power capability will be increased to 2.8 megawatts to support the STS.

With eight initial instruments, the capabilities of the STS will complement those of the First Target Station and HFIR by filling gaps in materials research that require the combined use of intense, cold (longer wavelength) neutrons and instruments that are optimized for studying a wider range of materials. Together, these three facilities will form an unbeatable combination that will maintain U.S. global leadership in neutron science capabilities.

"Operating a newly upgraded, world-class science facility for 1,250 hours right out of the gate is remarkable in its own right, but doing so with an availability level of over 96% is amazing," said Jens Dilling, associate laboratory director for ORNL's Neutron Sciences Directorate. "This success bodes well for the future of neutron science discoveries at ORNL and for the global neutron user community." Scientists conducting experiments with neutrons benefitted immediately from the PPU upgrades, which provided approximately 20% more neutron flux, improved resolution and the resulting increase in data quality.

"After six years of innovative planning and hard work, including persevering through a global pandemic, the project was delivered ahead of schedule and under budget. This testifies to the expertise and determination of all the people involved," said PPU Project Director Mark Champion.

In April, the PPU project team finished installing and testing the new hardware and ancillary systems required for beam commissioning and operations, which began in June and July, respectively. The SNS accelerator's energy was increased to enable generating the additional beam power intended for the first and second target stations.

"Extra beam power is only useful if we can use it reliably, so in addition to the SNS linear accelerator upgrades, the PPU project supported a team that developed a new target capable of handling the much higher 2.0 megawatts of beam power intended for the First Target Station," said Drew Winder, the lead for SNS's Source Development and Engineering group. "The new target was designed from the ground up, using all we'd learned from years of operation, and supports higher gas injection flows. Gas injection mixes helium bubbles into the flowing mercury to reduce fatigue and damage inside a target."

"Now that the project is wrapping up, we can already see some of the benefits of having the people who will be operating the upgraded facility also be the people who executed the upgrade," said ORNL's Research Accelerator Division Director Fulvia Pilat. "Their in-depth understanding of how the systems are constructed and how they operate will enable performance beyond even what we predicted when the project was first designed."

Beam power on the First Target Station will be further ramped up to the 2.0-megawatt level over the next two years.

SNS and HFIR are DOE Office of Science user facilities.

UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. - Paul Boisvert