2 May 2006
Neutron Source Fires Up
by Kate Melville
After years of eagerly anticipating its completion, scientists have finally witnessed the United States Department of Energy's (DOE) Spallation Neutron Source (SNS) in action at the Oak Ridge National Laboratory (ORNL). In a test conducted in the early hours of April 28, a pulse of protons successfully "spalled" neutrons from the nuclei of mercury. Researchers working on the project believe that this achievement will herald a new generation of materials research, which could lead to stronger and lighter airplanes, next generation batteries and fuel cells, and target specific time-released drugs.
The research team harvested their first neutrons after shooting a pulse of protons from the SNS's accelerator complex and hitting a mercury target at just under the speed of light. The mercury nuclei are relieved of their neutrons as the proton pulse initiates a process known as "spallation," where parts of a material are freed from a body after an impact or stress.
The team explained that despite the linac (linear particle accelerator) not operating at its intended 1.4 megawatt power, the mercury target was still bombarded by trillions of protons from a beam 8 times more powerful than the previous leading pulsed spallation source. This awesome power is predicted to provide researchers a net improvement in measured neutron beam intensity by a factor of 50 - 100.
"To have observed 'first neutrons' on the initial SNS run is a tribute to the men and women who have worked so hard to design, construct, and now operate this magnificent facility," said Dr. Raymond L. Orbach, Director of the DOE Office of Science. "To bring a project of this scale and cost to completion on budget and ahead of schedule represents a model for all future large scale scientific projects to emulate. All of us owe all who have contributed to this achievement sincere thanks and appreciation for the opportunities you have now created for our world. It is a great moment for science."
The team claims that the mercury target is a completely new innovation, while also explaining that mercury was used in the target because it is heavier than other elements and laden with neutrons. Unlike materials such as tungsten, Mercury can absorb the pulses from the linac and accumulator ring without requiring water-cooling that reduces spallation efficacy.
With over 100,000 individual parts and coming in at a cost of a cool $1.4 billion, the SNS is the product of a major collaborative work incorporating 6 DOE labs. The SNS facility proceeded in stages, starting with linac's 1,000-foot front end, followed by its "warm" and "cold" sections and then the accumulator ring. Currently the target station is being completed, which will eventually be used to direct neutrons to 24 very specialized instruments. Plans for a future power upgrade and a second target station are also being drawn up. A fully operational SNS together with ORNL's recently upgraded High Flux Isotope Reactor will make the Oak Ridge facility the world's leading center for studying the structure and dynamics of materials.
"These first neutrons are representative of the technological breakthroughs required to establish the SNS as the world's leading facility for neutron research," said SNS Director Thom Mason. "We took on the challenges and technical risks involved in designing and delivering the linac, ring and target because we knew how much the scientific user community would benefit from the results."
The scope of the project reflects the ultimate benefits that the SNS will bring to science and technology, as an increased understanding of material structures will almost certainly lead to an unlimited number of innovations. Each year, 2000 researchers from the US and abroad are set to use the facility to conduct materials research that will hopefully form the basis of new technologies in telecommunications, manufacturing, transportation, information technology, biotechnology and health.
Source: Oak Ridge National Laboratory