The Spallation Neutron Source achieves 20 years on target

In April, the world's most powerful accelerator-based neutron source celebrates 20 years of scientific achievements enabled by safe, reliable operations. The target is what makes it happen.

Since coming online in 2006, the Spallation Neutron Source at the Department of Energy's Oak Ridge National Laboratory has celebrated many milestones, including being the first to successfully incorporate a liquid mercury target with help from the Japan Proton Accelerator Research Complex (J-PARC).

"In the beginning, there were a lot of questions about how the target would work," said Drew Winder, Source Development and Engineering Group Leader at the SNS. "We've pushed the target to its limit over the years to find out what the limits are, and then we update it to move past those limits."

Most recently, the limit has been reaching and maintaining 2.0 megawatts (MW), which the facility aims to achieve this spring thanks to the Proton Power Upgrade project that doubled the power capability of SNS's linear accelerator from 1.4 to 2.8 MW.

Thousands of scientists from around the world apply each year to complete their research at the SNS and its sister neutron source, the High Flux Isotope Reactor (HFIR). A scientific panel chooses the most promising proposals and scientists whose proposals are selected use the facilities and instruments free of charge in return for making their data and findings public.

Neutron scattering research leads to breakthroughs in new materials and innovations in critical areas, including quantum, artificial intelligence, manufacturing, energy, medicine and national security.

How the liquid mercury target works

Made of steel, the target system, including pumps, pipes, and heat exchangers, contains 20 tons of swirling liquid mercury. The target vessel circulates one ton of mercury at any particular time when operating. During neutron production, 60 pulses of protons bombard the target and release energy that is roughly equal to a stick of dynamite exploding every second. When the high-energy protons make contact with the target, neutrons are "spalled" or released, hence the name Spallation Neutron Source.

The neutrons are then guided to the beam tubes attached to the facility's instruments, where they are used in to further breakthroughs in many industries, including automotive, aerospace, steel, defense, industrial materials, energy storage, data storage, biomedicine and more. These breakthroughs help address the 21^st century's major scientific challenges.

What's next? Artificial intelligence

There are plans to incorporate artificial intelligence to support the target, which aligns with DOE's Genesis Mission, a bold new endeavor to build the world's most powerful scientific platform to accelerate discovery science, strengthen national security, and drive energy innovation. Winder's team is working with experts from other ORNL groups, such as the Research Accelerator Division and the Fusion and Fission Energy and Science Directorate, on an algorithm that will help operators watch the system and add alerts, something Winder explained is vital for a facility such as SNS's First Target Station.

"Unlike other facilities that operate at a relatively steady state, we have a lot of beam trips and are always pushing the limits, so we need something to help look for anomalies when we turn the power up," said Winder.

The Second Target Station

The Proton Power Upgrade (PPU) project increased the power of the SNS to prepare for the construction of a Second Target Station (STS). The PPU included building a connector between the accelerator and the planned STS, which will operate using a rotating tungsten target.

Unlike FTS's mercury target, the tungsten target at STS will rotate so each proton pulse impacts different sections of the target, allowing the energy from the protons to spread instead of repeatedly hitting the same spot, increasing the target's lifespan.

The capabilities of the STS will complement those of the SNS First Target Station (FTS) and HFIR, by filling gaps in materials research that require the use of intense, cold (longer wavelength) neutrons. Together, these three facilities form an unbeatable combination that will maintain U.S. global leadership in neutron science capabilities.

HFIR and SNS 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. - Kaeli Dickert