A team of eight scientists and technicians in the Neutron Sciences Directorate has won a prestigious R&D 100 Award from R&D Magazine for developing a highly efficient new detector system that helps take pressure off dwindling worldwide supplies of 3He as an active neutron converter.
The award was for development of the wavelength-shifting scintillator neutron detector (WLS), which uses 6Li as a neutron convertor instead of the conventional 3He. The annual R&D 100s, now in their 50th year, recognize the 100 most technologically significant products introduced into the market over the past year.
The award goes to Lloyd Clonts, Ronald Cooper (retired), Lowell Crow, Yacouba Diawara, Bruce Hannan, Jason Hodges, Richard Riedel, and Cai-Lin Wang of NScD. The team developed the detector in partnership with PartTec, Ltd., of Bloomington, Indiana. The award is one of nine R&D 100s won at Oak Ridge National Laboratory in 2012.
“The detector has been in development for 8 years,” said Diawara, the detector group leader at NScD. “When we started this project, there was no concern about the availability of 3He. We have been fortunate in this sense because we had already been working on this, trying to find alternatives and to see how these might compare to 3He.
“It turned out to be really as good as 3He, and an advantage is that we now have an alternative to that detector element. It is at about 95% of 3He 8-pack efficiency, at 1 Ångstrom and 5 mm position resolution, in one axis.” The WLS is currently installed on two instruments at ORNL’s Spallation Neutron Source: VULCAN, an engineering materials diffractometer, and POWGEN, a time-of-flight powder diffractometer. The WLS system can be installed at several other instruments at both SNS and the High Flux Isotope Reactor and will be available for installation at neutron facilities worldwide.
WLS has a high-absorption cross section for neutrons and a low sensitivity to gamma rays owing to the low density and low atomic number of the solid scintillator materials (LiF/ZnS:Ag). As the scintillator absorbs a neutron, it emits a pulse of light, or scintillation. Electronics can detect this scintillation and determine when and where it occurred.
Because the WLS detector can determine the time and position of the neutron captured, it enables extremely accurate neutron time-of-flight measurements. An individual detector module has a 0.3 m2 sensitive area, low power requirements, and digital communication capability.
These factors make it attractive not only to neutron science facilities, but also for security applications. It can monitor land, air, and sea shipments for the presence of fissionable materials.
Although the new detector will have broad applicability at neutron sources, it is not suited for all neutron instruments. “There are still many instruments where detectors with higher spatial resolution and very high count rates are required. In these cases, we still need 3He,” Diawara said.
Funding for the research came from the Department of Energy’s Office of Basic Energy Sciences.
Winners of the R&D 100 Awards are selected by an independent judging panel and the editors of R&D Magazine. The publication serves research scientists, engineers, and other technical staff members at high-tech industrial companies and public and private laboratories around the world.
