The Spallation Neutron Source (SNS) is an accelerator-based

neutron source A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear p ...

facility in the U.S. that provides the most intense pulsed

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

beams in the world for scientific research and industrial development.In 2007, SNS was entered into th
Guinness Book of World Records
as the most powerful pulsed spallation source. Each year, the facility hosts hundreds of researchers from universities, national laboratories, and industry, who conduct basic and applied research and technology development using neutrons. SNS is part of

Oak Ridge National Laboratory Oak Ridge National Laboratory (ORNL) is a federally funded research and development centers, federally funded research and development center in Oak Ridge, Tennessee, United States. Founded in 1943, the laboratory is sponsored by the United Sta ...

, which is managed by UT-Battelle for the

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and energy production, the research and development of nuclear power, the military's nuclear w ...

(DOE). SNS is a DOE Office of Science user facility, and it is open to scientists and researchers from all over the world.

Neutron scattering research

Neutron scattering Neutron scattering, the irregular dispersal of free neutrons by matter, can refer to either the naturally occurring physical process itself or to the man-made experimental techniques that use the natural process for investigating materials. Th ...

allows scientists to count scattered neutrons, measure their energies and the angles at which they scatter, and map their final positions. This information can reveal the molecular and magnetic structure and behavior of materials, such as high-temperature

superconductors Superconductivity is a set of physical properties observed in superconductors: materials where electrical resistance vanishes and magnetic fields are expelled from the material. Unlike an ordinary metallic conductor, whose resistance decreases ...

polymers A polymer () is a substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, b ...

, metals, and biological samples. In addition to studies focused on fundamental physics, neutron scattering research has applications in

structural biology Structural biology deals with structural analysis of living material (formed, composed of, and/or maintained and refined by living cells) at every level of organization. Early structural biologists throughout the 19th and early 20th centuries we ...

and

biotechnology Biotechnology is a multidisciplinary field that involves the integration of natural sciences and Engineering Science, engineering sciences in order to achieve the application of organisms and parts thereof for products and services. Specialists ...

, magnetism and superconductivity, chemical and engineering materials,

nanotechnology Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing propertie ...

, complex fluids, and others.

Spallation process

The spallation process at SNS begins with negatively charged

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

ions that are produced by an

ion source An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines. Electron ionization Elect ...

. Each ion consists of a

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

orbited by two

electrons The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

. The ions are injected into a

linear particle accelerator A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of Oscillation, oscillating electric potentials along ...

which accelerates them to an energy of about one GeV (or to about 90% the

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

). The ions pass through a foil which strips off each ion's two electrons, converting it to a proton. The protons pass into a ring-shaped structure, a proton accumulator ring, where they spin around at very high speeds and accumulate in "bunches." Each bunch of protons is released from the ring as a pulse, at a rate of 60 times per second (60

hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...

). The high-energy proton pulses strike a target of liquid mercury, where spallation occurs. The spalled neutrons are then slowed in a moderator and guided through beam lines to areas containing special instruments where they are used in a wide variety of experiments.

History

Most of the world's

s were built decades ago, and although the uses and demand for neutrons have increased throughout the years, few new sources have been built. To fill that need for a new, improved neutron source, the DOE Office of Basic Energy Sciences funded the construction of SNS, which would provide the most intense pulsed neutron beams in the world for scientific research and industrial development. The construction of SNS was a partnership of six DOE national laboratories: Argonne, Brookhaven, Lawrence Berkeley, Los Alamos, Oak Ridge, and Jefferson. This collaboration was one of the largest of its kind in U.S. scientific history and was used to bring together the best minds and experience from many different fields. After more than five years of construction and a cost of $1.4 billion, SNS was completed in April 2006. The first three instruments began commissioning and were available to the scientific community in August 2007. As of 2017, 20 instruments have been completed, and SNS is hosting about 1,400 researchers per year.

References

External links

* * T. E. Mason et al., "The Spallation Neutron Source: A Powerful Tool for Materials Research,
arXiv:physics/0007068v1.

"SNS: Neutrons for 'molecular movies,'" ''Symmetry,'' vol. 03(05), Jun/Jul, 2006.
{{United States Department of Energy Types of magnets Materials science organizations Nuclear physics Particle physics facilities United States Department of Energy Oak Ridge National Laboratory Scattering Superconductivity Neutron facilities Buildings and structures in Roane County, Tennessee Neutron sources Fixed-target experiments

Neutron scattering research

Spallation process

History

See also

References

External links