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 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, this 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 U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research an ...

, 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 manages the research and development of nuclear power and nuclear weapons in the United Stat ...

(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,

polymers A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

metals A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typical ...

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

structural biology Structural biology is a field that is many centuries old which, and as defined by the Journal of Structural Biology, deals with structural analysis of living material (formed, composed of, and/or maintained and refined by living cells) at every le ...

and

biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used ...

, magnetism and superconductivity, chemical and engineering materials, nanotechnology,

complex fluids Complex fluids are mixtures that have a coexistence between two phases: solid–liquid ( suspensions or solutions of macromolecules such as polymers), solid–gas ( granular), liquid–gas (foams) or liquid–liquid (emulsions). They exhibit unusu ...

, and others.

How SNS works

The spallation process at SNS begins with negatively charged

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

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 Electron ...

. Each ion consists of a proton orbited by two

electrons The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

. 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 oscillating electric potentials along a linear b ...

, or linac, 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 that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...

). 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), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that o ...

). The high-energy proton pulses strike a target of liquid mercury, where spallation occurs. The

spalled Spall are fragments of a material that are broken off a larger solid body. It can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball ...

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 Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States national laboratory that is owned by, and conducts scientific research on behalf of, the United States Department of Energy. Located in ...

, 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, a total of 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 Anderson County, Tennessee Buildings and structures in Roane County, Tennessee Neutron sources Fixed-target experiments

Neutron scattering research

How SNS works

History

See also

References

External links