Why Was SNS Built ?
Evolution of the performance of reactors and pulsed spallation sources. In recent years, dramatic improvements in accelerator technology have made it possible to design and construct a source to produce very intense neutron pulses (updated from Neutron Scattering, K. Skold and D. L. Price, eds., Academic Press, 1986).
Neutron scattering is used by a variety of scientific disciplines to study the arrangement, motion, and interaction of atoms in materials. Neutron scattering is important because it provides valuable information that often cannot be obtained using other techniques, such as optical spectroscopies, electron microscopy, and x-ray diffraction. Scientists need all these techniques to provide the maximum amount of information on materials.
Why a new spallation source?
Although the United States pioneered the development and use of early neutron sources, Europeans and the Japanese have capitalized on this early experience and developed newer sources that have been the best in the world for the past 15 to 20 years. Even these sources, however, are quite old.
What are the advantages of a pulsed spallation source?
Neutrons are separated in energy after traveling over a fixed path (L), permitting neutrons of many different energies and wavelengths to be used for experiments.
Each pulse contains neutrons of a range of wavelengths and energies; the highest-energy neutrons have the shortest wavelengths, and the lowest-energy neutrons have the longest wavelengths. Because thermal neutrons move slowly enough, their progress can be timed accurately over short distances. Each pulse contains neutrons of all thermal energies, so neutrons of different energies can be separated by letting them travel down a short path of a few meters. The high-energy neutrons reach the sample ahead of the medium-energy neutrons, and the lowest-energy neutrons take the longest to arrive at the sample. Because the neutron energies are spread out in time, the energy of an individual neutron is easily determined by its "time of flight" to the sample. Because thermal neutrons of all energies are available for use in scattering experiments, the time-of-flight technique enables the collection of many data points for each source pulse reaching a sample. Furthermore, it is not required that the neutron detectors move during an experiment, making it easy to arrange large detector arrays or multidetectors around the sample.
How is SNS bringing new opportunities to the neutron science community?
Because SNS is the most advanced and powerful pulsed neutron source in the world, it's providing research opportunities unavailable elsewhere. Hence, this unique facility is attracting scientists and researchers in a variety of disciplines from all over the globe. Studies conducted at SNS go beyond basic research and development and are leading to technological and industrial breakthroughs that will ultimately benefit not only the scientific community but also the business and industrial communities.
