World-Class Neutron Source Takes A Break For Major Proton Power Upgrade


The Spallation Neutron Source at Oak Ridge National Laboratory — already the world’s most powerful accelerator-based neutron source — will be on a planned hiatus through June 2024 as crews work to upgrade the facility. 

Much of the work — part of the facility’s Proton Power Upgrade project — will involve building a connector between the accelerator and the planned Second Target Station at SNS. When complete, the PPU project will bring the accelerator up to 2.8 megawatts from its current record-breaking 1.7 megawatts of beam power.

Workers will add about 3,000 square feet of concrete tunnel, the “stub,” which will integrate with an existing tunnel. Construction tasks include associated structures, roofing, geomembrane liner, tunnel waterproofing, electrical, fire alarm, ventilation systems and controls.

“The construction crews have performed all of the excavation work and are transitioning to tunnel base and wall construction,” said ORNL’s Mark Champion, PPU project manager. 

The stub is scheduled to be completed within six months, by the end of February, and most of the rest of this outage will involve installing new components and systems to complete the PPU project.

That work includes:

  • Installing three new cryomodules, adding more radio-frequency stations and upgrading two high-voltage units to support new 3.0 megawatt klystrons.
  • Installing an injection dump imaging system and new magnets and upgrading deionized water systems, power supplies and a beam power limit system.
  • Installing a new liquid hydrogen refill system, mercury overflow tank and target complete with gas injection and recirculation system.
  • Completing controls integration. 

The upgrade will increase the flow of neutrons — known as the neutron flux — to the First Target Station, or FTS, and eventually also power the STS. 

Power to the FTS — which produces thermal neutrons to analyze samples down to the atomic scale — will increase to 2.0 megawatts, enabling new scientific discoveries in such areas as superconductors, energy materials such as those used in batteries, and basic physics. The additional power will be split via the stub, to power the STS, which will have the world’s highest peak brightness of neutrons, tailored for probing soft matter such as polymers and biological materials, and complex engineering materials. This is used in vaccine research, advanced batteries and for decarbonization studies.

“It’s very gratifying to reach one of the final stages of the project after several years of planning, design and engineering,” said ORNL’s John Galambos, PPU project director. “It’s a huge tribute to the skills and dedication of the entire PPU team and our partner labs that the project has remained on schedule and on budget despite unprecedented challenges, including Covid-19 and subsequent supply chain issues.”

The Spallation Neutron Source is an Office of Science user facility at ORNL.

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