Plans for Oak Ridge expansion accelerating

From the empty space in the linear accelerator building to the giant mound of dirt out back, it’s clear Oak Ridge National Laboratory’s Spallation Neutron Source has room to grow.

The Department of Energy and six national labs collaborated to make Oak Ridge’s neutron source during the 1990s. Upon its completion in 2006, it was the most powerful and in-demand neutron source in the world. As such, it was designed to expand as needed.

“Ever since the SNS was first conceived, we planned and designed and built it in a way that would allow us to upgrade it,” said Paul Langan, ORNL associate laboratory director for neutron sciences. “We designed this place to accommodate a power upgrade of the accelerator complex, and then to support a second target station with more instruments and very new capabilities for emerging science.”

When it opened, about 60 scientists came to run experiments on the site’s accelerator beams, which strip hydrogen atoms into protons, fire the protons across three football fields at 88 percent the speed

of light, compress them, and then slam them into a mercury target.

The stress of the bombardment causes the mercury in the target to spall, or break apart. When it does, the mercury emits neutrons.

Scientists have used those neutrons for a range of scientific applications, from creating better computer storage and batteries to designing better cancer drugs, and even to the discovery of a new element on the periodic table.

HIGH DEMAND FOR HIGH ENERGY NEUTRONS

Demand for beam time at the SNS has increased in the 11 years it has been up and running. About 900 experiments are performed at the facility each year. Scientists come from all over the world to use the neutron source, but only one in three seeking beam time actually get it.

“It’s our job to increase access to our facilities and researchers so that we can accelerate scientific discoveries,” Langan said. “DOE agrees that our upgrades are absolutely central to the U.S. continuing to lead world science.”

An energy department review team just finished analyzing ORNL’s cost estimate for upgrading the linear accelerator’s proton power, the first step in constructing the second target. ORNL will go through another energy department review at the end of May. If it goes well, they can move forward with detailed construction planning.

The proton power upgrade will cost about $200 million, and the second target station construction will cost about $1 billion. Ideally, the two projects will move forward at the same time. Langan said, depending on energy department funding and approval, they may be ready to break ground in the next few years.

“This is taxpayers’ money, and we want to be the best possible stewards of that money,” Langan said. “Our sponsors [Department of Energy] are working with us to move us forward with our conceptual design, our cost estimate and our schedule for those major upgrades. Everything depends on the economic environment and budget and that kind of thing.”

The timeline is picking up on the project, and while setting a construction date will depend on funding and energy department priorities, the excitement at SNS is visible. Someone has even placed a small sign on the giant mound of earth behind the facility indicating the exact spot that will be home to the new target.

DIFFERENT NEUTRONS, DIFFERENT SCIENCE

Since the construction of the neutron source, ORNL has led the scientific world in mercury target technology. Mercury spalls out, or splinters, high energy neutrons that are useful for looking at the structure and dynamics of matter in high resolution.

The second target will be made of tungsten. The proton pulses that hit the tungsten will be much more intense and compressed than the ones hitting the mercury target. When struck, the new target will produce colder and lower-energy neutrons that will let scientists examine matter at a greater range.

Those will have better applications in biological sciences, like designing new cancer drugs.

“We need to understand those things at bigger scales and with larger motions and at many different levels,” Langan said. “With the new target station, we’ll be able to look at matter simultaneously at the microscopic level all the way up to the visual level. It will be much better for designing drugs to treat really complex biological diseases.”

The new target also will have more applications in soft material sciences such as 3-D printing and working with composites, plastics and polymers.