Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of the structure of the material. The technique is similar to X-ray diffraction but due to their different scattering properties, neutrons and X-rays provide complementary information: X-Rays are suited for superficial analysis, strong x-rays from synchrotron radiation are suited for shallow depths or thin specimens, while neutrons having high penetration depth are suited for bulk samples.
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. The natural/physical phenomenon is of elemental importance in nuclear engineering and the nuclear sciences. Regarding the experimental technique, understanding and manipulating neutron scattering is fundamental to the applications used in crystallography, physics, physical chemistry, biophysics, and materials research.
A subcritical reactor is a nuclear fission reactor concept that produces fission without achieving criticality. Instead of sustaining a chain reaction, a subcritical reactor uses additional neutrons from an outside source. There are two general classes of such devices. One uses neutrons provided by a nuclear fusion machine, a concept known as a fusion–fission hybrid. The other uses neutrons created through spallation of heavy nuclei by charged particles such as protons accelerated by a particle accelerator, a concept known as an accelerator-driven system (ADS) or accelerator-driven sub-critical reactor.
Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary physics, spallation describes meteoritic impacts on a planetary surface and the effects of stellar winds and cosmic rays on planetary atmospheres and surfaces. In the context of mining or geology, spallation can refer to pieces of rock breaking off a rock face due to the internal stresses in the rock; it commonly occurs on mine shaft walls. In the context of anthropology, spallation is a process used to make stone tools such as arrowheads by knapping. In nuclear physics, spallation is the process in which a heavy nucleus emits numerous nucleons as a result of being hit by a high-energy particle, thus greatly reducing its atomic weight. In industrial processes and bioprocessing the loss of tubing material due to the repeated flexing of the tubing within a peristaltic pump is termed spallation.
The Open-pool Australian lightwater reactor (OPAL) is a 20 megawatt (MW) swimming pool nuclear research reactor. Officially opened in April 2007, it replaced the High Flux Australian Reactor as Australia's only nuclear reactor, and is located at the Australian Nuclear Science and Technology Organisation (ANSTO) Research Establishment in Lucas Heights, New South Wales, a suburb of Sydney. Both OPAL and its predecessor have been known simply as the Lucas Heights reactor.
The Spallation Neutron Source (SNS) is an accelerator-based neutron source facility in the U.S. that provides the most intense pulsed neutron beams in the world for scientific research and industrial development. 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, which is managed by UT-Battelle for the United States Department of Energy (DOE). SNS is a DOE Office of Science user facility, and it is open to scientists and researchers from all over the world.
Muon spin spectroscopy, also known as μSR, is an experimental technique based on the implantation of spin-polarized muons in matter and on the detection of the influence of the atomic, molecular or crystalline surroundings on their spin motion. The motion of the muon spin is due to the magnetic field experienced by the particle and may provide information on its local environment in a very similar way to other magnetic resonance techniques, such as electron spin resonance and, more closely, nuclear magnetic resonance (NMR).
Research reactors are nuclear fission-based nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion.
The ISIS Neutron and Muon Source is a pulsed neutron and muon source, established 1984 at the Rutherford Appleton Laboratory of the Science and Technology Facilities Council, on the Harwell Science and Innovation Campus in Oxfordshire, United Kingdom. It uses the techniques of muon spectroscopy and neutron scattering to probe the structure and dynamics of condensed matter on a microscopic scale ranging from the subatomic to the macromolecular.
Neutron backscattering is one of several inelastic neutron scattering techniques. Backscattering from monochromator and analyzer crystals is used to achieve an energy resolution on the order of a microelectronvolt (μeV). Neutron backscattering experiments are performed to study atomic or molecular motion on a nanosecond time scale.
Triple-axis spectrometry is a technique used in conjunction with inelastic neutron scattering. The instrument is referred to as triple-axis spectrometer. It allows measurement of the scattering function at any point in energy and momentum space physically accessible by the spectrometer.
Neutron spin echo spectroscopy is an inelastic neutron scattering technique invented by Ferenc Mezei in the 1970s and developed in collaboration with John Hayter. In recognition of his work and in other areas, Mezei was awarded the first Walter Haelg Prize in 1999.
The European Spallation Source ERIC (ESS) is a multi-disciplinary research facility currently under construction in Lund, Sweden. Its Data Management and Software Centre (DMSC) is situated in Copenhagen, Denmark. Its 13 European contributor countries are partners in the construction and operation of the ESS. The ESS is scheduled to begin its scientific user program in 2027, when the construction phase is set to be completed. The ESS will enable scientists to observe and understand basic atomic structures and forces, which is currently unachievable with other neutron sources in terms of lengths and time scales. The research facility is located close to the MAX IV Laboratory, which conducts synchrotron radiation research. The construction of the facility began in the summer of 2014 and the first science results are planned for 2027.
The NA58 experiment, or COMPASS is a 60-metre-long fixed-target experiment at the M2 beam line of the SPS at CERN. The experimental hall is located at the CERN North Area, close to the French village of Prévessin-Moëns. The experiment is a two-staged spectrometer with numerous tracking detectors, particle identification and calorimetry. The physics results are extracted by recording and analysing the final states of the scattering processes.
A neutron research facility is most commonly a big laboratory operating a large-scale neutron source that provides thermal neutrons to a suite of research instruments. The neutron source usually is a research reactor or a spallation source. In some cases, a smaller facility will provide high energy neutrons using existing neutron generator technologies.
The Los Alamos Neutron Science Center (LANSCE), formerly known as the Los Alamos Meson Physics Facility (LAMPF), is one of the world's most powerful linear accelerators. It is located in Los Alamos National Laboratory in New Mexico in Technical Area 53. It was the most powerful linear accelerator in the world when it was opened in June 1972. The technology used in the accelerator was developed under the direction of nuclear physicist Louis Rosen. The facility is capable of accelerating protons up to 800 MeV. Multiple beamlines allow for a variety of experiments to be run at once, and the facility is used for many types of research in materials testing and neutron science. It is also used for medical radioisotope production.
A Fixed-Field alternating gradient Accelerator is a circular particle accelerator concept that can be characterized by its time-independent magnetic fields and the use of alternating gradient strong focusing.
AGATA, for Advanced GAmma Tracking Array, is a High-Purity Germanium (HPGe) semiconductor detector array for γ-ray spectroscopy that is based on the novel γ-ray tracking concept. It offers excellent position resolution thanks to high segmentation of individual HPGe crystals and refined pulse-shape analysis algorithms, and high detection efficiency and peak-to-total ratio thanks to elimination of Compton-suppression shielding in favour of tracking the path of γ rays through the spectrometer as they are scattered from one HPGe crystal to another. AGATA is being built and operated by a collaboration including 40 research institutions from thirteen countries in Europe. The first Memorandum of Understanding for the construction of AGATA has been signed in 2003 by the participating institutions; the updated Memorandum of Understanding, signed in 2021, foresees the extension of the array to a 3π configuration by 2030. Over the years, AGATA has been steadily growing, and currently is operated in a 1π configuration at Legnaro National Laboratories after campaigns at GANIL (2014-2021), GSI Helmholtz Centre for Heavy Ion Research (2012-2014) and Legnaro National Laboratories (2010-2011). AGATA can be coupled with ancillary detectors, such as magnetic spectrometers, fast-timing detectors, charged particles or neutron detectors.
Zoë Althea Bowden is a British physicist and instrumentation scientist who was involved in the construction of the ISIS Neutron and Muon Source. She was awarded an Order of the British Empire in the 2023 New Year Honours in recognition of her services to science.
