Spallation Neutron Source

Spallation Neutron Source
Name	Spallation Neutron Source
Caption	Aerial view of the Oak Ridge National Laboratory campus showing the Spallation Neutron Source facility.
Established	2006
Research field	Neutron scattering
Director	Paul Langan
Location	Oak Ridge, Tennessee, United States
Operating agency	Oak Ridge National Laboratory for the United States Department of Energy
Website	https://neutrons.ornl.gov/sns

Spallation Neutron Source. It is one of the world's most powerful accelerator-based neutron source facilities, providing the most intense pulsed neutron beams for scientific research. Located at the Oak Ridge National Laboratory in Tennessee, it enables researchers to probe the atomic structure and dynamics of a vast array of materials. The facility is a user facility operated by the United States Department of Energy for researchers from academia, industry, and other national laboratories.

Overview

The primary purpose of this leading-edge facility is to produce neutrons for use in neutron scattering experiments, a technique analogous to X-ray diffraction but uniquely sensitive to lighter elements and magnetic properties. It operates as a national user facility, with beam time allocated through a competitive peer-review proposal system managed by the Oak Ridge National Laboratory. This ensures access for thousands of scientists annually from institutions like Massachusetts Institute of Technology, University of California, Berkeley, and international partners. The resulting research drives innovation in fields from condensed matter physics to pharmaceuticals.

Scientific principles

The facility generates neutrons not through nuclear fission but via a process called spallation. In this process, a high-energy proton beam from a linear accelerator and accumulator ring is directed onto a heavy metal target, typically made of liquid mercury. The impact of the protons "chips" or spalls neutrons loose from the target nuclei. These neutrons are then moderated by materials like liquid hydrogen or water to useful energies before being guided down beamlines to various instruments. This method, pioneered at facilities like the ISIS Neutron and Muon Source in the United Kingdom, provides extremely bright, pulsed neutron beams ideal for time-of-flight measurement techniques.

Major facilities

The central accelerator complex consists of a negative hydrogen ion source, a 1‑GeV linear accelerator, and a accumulator ring that compresses proton pulses before striking the target. Surrounding the target station are numerous instrument beamlines, each housing specialized spectrometers and diffractometers such as the EQ-SANS and SEQUOIA instruments. A second target station was authorized to expand capabilities. Supporting infrastructure includes extensive cryogenic plants, radiation shielding, and computing resources from the Oak Ridge Leadership Computing Facility. The facility often operates in concert with the adjacent High Flux Isotope Reactor.

Applications

Research conducted here has profound impacts across multiple scientific and industrial disciplines. In materials science, it reveals stresses in jet engine components and the behavior of novel superconductors. For biology, it elucidates the structure of complex proteins and membranes, aiding drug discovery for diseases like Alzheimer's disease. In chemistry, it tracks ions in next-generation battery materials like those for electric vehicles. Studies in geophysics probe the structure of magma and minerals under extreme conditions, while archaeology research has analyzed artifacts from ancient Rome.

Technical specifications

The accelerator produces proton pulses at 60 Hz, with a beam power of 1.4 megawatts, making it the highest-power pulsed spallation source globally. The target receives an average proton current of over 1 milliampere. Neutrons are delivered to over twenty beamlines, with instruments capable of achieving Angstrom-scale resolution and detecting processes occurring from picoseconds to microseconds. The facility's data acquisition systems handle petabytes of information annually, requiring advanced analysis software and high-performance computing support from the Oak Ridge Leadership Computing Facility.

History and development

The project was formally initiated in the 1990s, with construction beginning in 1999 under the management of the United States Department of Energy. A multi-laboratory partnership, including Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, and Argonne National Laboratory, contributed key components. First beam was achieved in April 2006, with the official dedication attended by officials like Secretary of Energy Samuel Bodman. Major upgrades, such as the Proton Power Upgrade project, continue to enhance its capabilities, ensuring it remains competitive with international peers like J-PARC in Japan and the future European Spallation Source in Sweden.

Category:Oak Ridge National Laboratory Category:Neutron facilities Category:Research institutes in Tennessee