Neutron Scattering

Neutron scattering was pioneered at ORNL by Cliff Schull and Ernie Wollan, with the first diffraction experiments being performed in 1945. Cliff Shull shared the 1994 Nobel Prize in Physics with Bertram Brockhouse, who pioneered the triple-axis technique.

Neutrons are an experimental tool for determining the positions, correlations and motions of atoms in condensed matter systems. The advantage is that the neutron wavelength is well-correlated to inter-atomic spacings and the neutron kinetic energy is well-matched to atomic dynamics in solids. Neutrons are weakly interacting and highly penetrating, which aid in analyzing scattering data.

Furthermore, the isotropic sensitivity of neutrons provide a level of contrast variation with scattering spectra, and so neutrons can also be used to measure the positions of light atoms as well as heavy ones. Finally, the magnetic moment of the neutron allows for neutron scattering from unpaired electron spins, and to discern magnetic ordering in materials.

Neutrons at ORNL

ORNL boasts 33 neutron scatering instruments: 13 at the High Flux Isotope Reactor (HFIR) and 20 at the Spallation Neutron Source (SNS). Both of these sources are continuously being upgraded to continue to function as world-leading sources of neutron scattering research. HFIR is planning for the replacement of the Be reflector in 2023-24, at which time the cold guide hall will be expanded and redesigned to house new and upgraded instruments. The SNS is currently constructing 2 new instruments, planned to be put into the user program in 2022 and 2023. That source is also in the midst of the Proton Power Upgrade (PPU) project that will double the power of the accelerator from 1.4 MW to 2.8 MW. This will provide more flux to the existing instruments, as well as add the capability to construct a Second Target Station (STS) with new time-of-flight instruments.

Every year, ORNL (in conjuction with the Advanced Photon Source at Argonne National Laboratory) hosts graduate students who are interested in learning more about neutron and x-ray scattering. Students receive lectures from active researchers, and hands-on tutorials interacting with instrument scientists on the neutron instruments. For more information, please see the NXS page.

My instrument responsibilities are currently in the Triple-Axis Team at HFIR. To learn more about HFIR, the triple-axis spectroscopy suite, and our instrument and experimental capabilities, please check the information below, or feel free to contact me.
High Flux Isotope Reactor
Operating at 85 MW, HFIR is the highest flux reactor-based source of neutrons for research in the United States, and it provides one of the highest steady-state neutron fluxes of any research reactor in the world. The thermal and cold neutrons produced by HFIR are used to study physics, chemistry, materials science, engineering, and biology. The intense neutron flux, constant power density, and constant-length fuel cycles are used by more than 500 researchers each year for neutron scattering research into the fundamental properties of condensed matter.
Learn more about HFIR
Triple Axis Spectroscopy
HFIR contains 4 instruments for performing triple-axis spectroscopy. Each is tailored to a particular class of experiments, from parametric studies to polarization analysis, from cold neutrons to thermal neutrons. Triple-axis spectroscopy provides the most precise neutron measurements of a specific region of Q-E space, and is used for precision studies of magnetic ordering, spin waves, phonons, and other excitations.
Learn more about Spectroscopy
HB-1A FIE-TAX
The HB-1A Triple-Axis-Spectrometer (FIE-TAX) at the High Flux Isotope Reactor operates at a fixed incident energy by employing a double-bounce pyrolytic graphite monochromator system. This setup provides HB-1A with a very clean beam nearly free of higher-order contamination neutrons. This setup, combined with the use of an analyzer for energy discrimination, ensures that HB-1A has an excellent signal-to-noise ratio for magnetic diffraction studies.
Learn more about HB-1A
HB-1 PTAX
HB-1 (PTAX) is specifically designed for polarized beam measurements, but it is also a highly efficient general-purpose unpolarized neutron spectrometer. The choice of two monochromator plugs gives this instrument great versatility. The polarizing plug accommodates the fixed vertical focusing Heusler alloy monochromator with a vertical guide field, and can accomodate half-polarized measurements as well as full polarization analysis. The unpolarized plug accommodates a pyrolitic graphite (PG) monochromator with variable vertical focusing.
Learn more about HB-1
HB-3 TAX
HB3 provides a very high neutron flux thanks to its location directly at the end of the beam tube that is situated slightly away from the tangential path toward the reactor core. A sapphire filter is placed before the monochromator to reduce epithermal neutrons. Inside the drum there are 3 monochromators mounted on a unit. They are pyrolytic graphite (PG), silicon, and beryllium each of which is equipped with vertical focusing device that keeps the beam height at 1 inch over a wide range of incident energies at the sample position. PG (002) provides the highest neutron intensity, while the unique high-quality Be (002) monochromator extends the energy range and provides good energy resolution at high energy transfers and the Si(111) crystals have no second-order reflection, thus providing a clean beam.
Learn more about HB-3
CG-4C CTAX
CG4C is a conventional cold neutron triple-axis spectrometer with variable incident energy and sample-analyzer distances. The cold guide bender and guide hall shielding reduce background levels, and the 15-cm-tall guide profile is well exploited by CG4C′s vertically focusing monochromator (PG 002). To enhance accommodation of strong magnetic fields at the sample position and simplify future polarization analysis, the amount of ferromagnetic material has been minimized in the construction of this instrument.
Learn more about CTAX
Sample Environment
The Sample Environment Group provides support for the development, deployment & operations of environments at both SNS & HFIR. Capabilities include temperature from 50 mK to 1600 C, magnetic fields up to 8 T and a wide variety of pressure cells. Additionally, the Sample Environment group can provide customized support, including electric field, in situ measurements and custom sample mounts.
Learn more about Sample Environment
HFIR/SNS User Resources
The User Office is responsible for many aspects of the User Program. From submitting a proposal to coordinating your site access and training, the User Office staff are available to assist and answer your questions. Each year, HFIR and the SNS host hundreds of users from all over the world. User office and beamline staff are available to assist you in all aspects of the process: from preparing and submitting proposals, to experiment preparation and execution, to data analysis and manuscript preparation.
Become a user

Do you have questions about HFIR capabilities or how to propose an experiment?

We are available to help at any stage of the process. Please feel free to contact any member of an instrument team. Contact me here:

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