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.