Neutron scientists awaken a sleeping giant after a nine-month hibernation and upgrade

What’s the best way to wake up a giant after a long nap? “Very carefully, and with a lot of planning,” said a smiling John Galambos. He was the project director of the Proton Power Upgrade, or PPU, project at Oak Ridge National Laboratory until he retired in July after more than 40 years at the laboratory. “It was an A-team effort that will benefit the advancement of science and technology for decades to come.”

The “giant” Galambos is talking about is the Spallation Neutron Source, or SNS, the country’s main source of pulsed neutron beams for research, which has just restarted after nine months of development work. The extended schedule allowed for the installation and testing of seven additional cryogenic modules and their additional 28 units, as well as supporting equipment—all designed to increase the 362-yard capacity. -long-long linear accelerator complex, or linac.

The installed linac will provide the First Observation Station at SNS with approximately 40% more than its original capacity of 1.4 megawatts, equivalent to 2.0 megawatts. More energy will produce more neutrons and increase the pace of scientific discovery across a wide variety of materials and technologies. To cope with the increased power, the accumulator ring and the SNS center objective were also improved with new electronics and supporting equipment.

Finally, the linac will also power the Second SNS Target Station, or STS, to produce the world’s brightest “cold” neutrons and enable studies of small and complex instruments.

Neutrons are used extensively in research, such as making new vaccines, analyzing advanced batteries and operating national defense systems. Neutron scattering at SNS and ORNL’s High Flux Isotope Reactor, or HFIR, is an important method for advancing material research to support the American economy and provide solutions to energy, transportation, biotechnology, quantum and space problems. some research.

Overcoming obstacles

Despite the global pandemic, supply chain issues and other unprecedented challenges, the ORNL team was able to complete the PPU project ahead of schedule and under budget.

“The PPU project exceeded all expectations of how it came together three years ahead of schedule despite major technical, logistical and global health challenges,” said Jens Dilling, laboratory director of associated with the Neutron Science Directorate. “Thanks to the tremendous efforts of ORNL staff and our collaborative partners at Jefferson Lab and Fermi National Laboratory, SNS will continue to serve as the world’s leading center for pulsed neutron research.”

The future looks brighter

The STS will produce the world’s highest beam of neutrons, designed to examine simple materials such as polymers and biological materials, and complex engineering materials. STS will provide 24 new instrument stations – starting with eight – for unprecedented experiments on complex matter.

Mark Champion is the new PPU project director after serving as project manager since PPU’s inception in 2016. “We want to acknowledge and thank the project team for all their hard work and dedication, ” he said. “But we don’t plan to rest. There is a lot of gas in the tank, and we need to continue to push the technology to enable science even more and more in the future.”

Jon Taylor, director of ORNL’s Neutron Scattering Division, said, “I know that our neutron scientists and outside researchers working at SNS are already benefiting from the record 1.7 megawatts enabled. is the PPU project in 2023. They have seen the improvements that the accelerator will make to their experiments, and they really want the full 2.0 megawatts that we will provide.”

Traveling at 167,000 kilometers per second

The linac uses electric fields to propel and accelerate protons to 90% the speed of light, or 167,000 kilometers per second. These protons pass through large magnets that guide them into a ring of accumulators 271 meters long.

There they are gathered together and directed 60 times per second into an area filled with 20 tons of mercury water. This is where protons knock neutrons out of mercury atoms. Finally, these “free” neutrons are brought down to the instruments where the scientists conduct their experiments.

The first third of the linac operates at room temperature, while the rest uses 81 superconducting cavities inside cryomodules that are cooled with liquid helium to just two degrees above zero. full (minus 460 degrees Fahrenheit).

A key part of the project involved building a curved tunnel extension from the existing accelerator to the site of the proposed Second Mission Station. Workers added an approximately 3,000-square-meter concrete tunnel, enclosed by an 18-meter-thick wall of more than 7,000 concrete blocks to provide radiation protection during normal operation of the SNS line. Other construction activities associated with the tunnel extension included installation of associated structures, roofing, geomembrane liners, tunnel waterproofing, electrical, fire alarm, ventilation and systems.

The long-term delay to install SNS ended in April 2024. The accelerator’s external readiness review was carried out the following month, and permission to conduct routine and routine work was granted. given in early June. Beam commissioning was completed in less than 30 days.

“The plan to raise the power after the PPU requires a gradual increase in the power of the network to the target and the annual hours of neutron production up to 2.0 MW and 5,000 hours, respectively, in the fiscal year 2027. However, since our sleeping giant is fully awake and working hard, it may be possible to increase the capacity of the network early, which can be profitable scientific production at the center,” said Champion.

The project is preparing a close report, lessons learned, and other documents as needed to support the US Department of Energy’s review of the project’s completion in early 2025.