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Neutron Physics Group

Welcome

The Neutron Physics group, located at the NIST Center for Neutron Research (NCNR), maintains and supports the nation's premier fundamental neutron physics user facilities, including a weak interactions neutron physics station, the Neutron Interferometry and Optics Facility (NIOF),  the Ultra Cold Neutron Facility (UCNF) and an He-3 based Neutron Polarized development facility. Our group has developed the nation's only high-resolution neutron imaging user facility (NIF) for fuel cell research. We maintain, and disseminate measurement standards through both evaluation and experimental work. 

The group is at the forefront of basic research with neutrons.  Experiments involve precision measurements of symmetries and parameters of the "weak" nuclear interaction, including measurement of the lifetime of neutrons using thermal and ultra-cold neutron improved cold neutron counting techniques, setting a limit on the time-reversal asymmetry coefficient, and radiative decay of the neutron. The neutron interferometry program provides the world's most accurate measurement of neutron coherent scattering lengths important to materials science research and modeling of the nuclear potentials; during 2007-2008, new interferometry experiments to determine the charge distribution of the neutron, and reciprocal space imaging were carried out.  We  are developing and promoting the applications of efficient neutron spin filters based on laser-polarized He-3.  We are pursuing applications for these filters at the NCNR, the Intense Pulsed Neutron Source at Argonne National Laboratory, and the Los Alamos Neutron Science Center. 

We are enhancing our technical infrastructure to better support neutron standards for national security needs.  In addition, we are developing advanced liquid scintillation neutron spectrometry techniques for characterization of neutron fields and for detection of concealed neutron sources with low false-positive rates.  We are participating in a Consultative Committee for Ionizing Radiation (CCRI) comparison of thermal neutron fluence rate measurements, characterizing four different beam qualities at the NCNR, and carrying out comparisons of NIST standard neutron sources. We are also leading an effort that will result in a new international evaluation of neutron cross-section standards.  We provide two main calibration services: measurement of the emission rate of neutron sources, and calibration of neutron detectors used for personnel protection.  Calibrations not falling within these services can be arranged as a special test.

We are applying neutron-imaging methods for industrial research on water transport in fuel cells and on hydrogen distribution in hydrogen storage devices.  This facility has provided critical services to major automotive and fuel cell companies during 2007-2010. This is a high demand and high profile nationally recognized program. 

In summary, the NI&D group provides measurement services, standards, and fundamental research in support of NIST's mission as it relates to neutron technology and neutron physics.  The national interests served include industrial research and development, national defense, homeland security, higher education, electric power production, and, more specifically, neutron imaging, scientific instrument calibration and development, neutron source calibrations, detection of concealed nuclear materials, radiation protection, and nuclear and particle physics data.

Programs/Projects

Evolution of Image Spatial Resolution—Measuring the through-plane water content in a hydrogen fuel cell is critical to understanding this complicated heat and mass transport environment, where the waste heat produces temperature …

New Calibration Service for 14 MeV Neutron Generators—A new calibration service for 14 MeV neutron generators is being developed.  The calibrations may be done at NIST or at a customer site, by activation of a standardized aluminum ring, with NaI …

Neutron Device Calibrations—NIST provides the national reference for the calibration of neutron radiation detectors and for neutron personnel dosimeters. 

Neutron Cross Section Standards—NIST continues to be deeply involved with measurements and evaluations of neutron cross section standards.  NIST maintains a limited experimental effort focused on improvements to the database of …

Calibrated Neutron Sources—ANSI N42.35 requires 252Cf neutron sources encapsulated in 1 cm of steel with a fluence of 2x104 n/s ±20%. 

Use of Quantum Error Coding in a 4-Blade Neutron Interferometer—We have designed a new type of neutron interferometer, which will be less sensitive to slow vibrations.

Measurement of the Neutron Magnetic Dipole Moment Using Schwinger Scattering—This experiment will measure Schwinger scattering in silicon. Previous attempts done by Shull and others did not produce the expected results. The successful realization of Schwinger scattering …

Search for Time Reversal Violation in Polarized Neutron Decay (emiT)—The "emiT" experiment searches for - or will set an improved upper bound on - the time-reversal asymmetry term in neutron beta decay. It does so by measuring electron-proton coincidence events from …

Neutron Source Strength Calibrations—The neutron source calibration facility operated by NIST is a world-class calibration laboratory providing neutron source  calibration services for radioisotopic sources with neutron emission rates …

New Manganese Sulfate Bath—Description: Many neutron sources required by Homeland Security have a lower neutron emission rate than is appropriate for the NIST calibration facility, a Manganese Sulfate Bath system. 

Characterization of Porous Transport Media for Hydrogen Fuel Cells—Efficiently managing water transport in proton exchange membrane fuel cells (PEMFCs) is critical to the performance, cost, and durability in order for this technology to become the next automobile …

Wide-Angle Neutron Polarization Analysis —The capabilities of many neutron scattering instruments would be greatly enhanced by neutron polarization analyzers that can cover a wide angular range. 

Neutron Tomography of Hydrogen Storage Bed—Future hydrogen fuel cell vehicles will require hydrogen storage vessels that efficiently store and quickly release the hydrogen fuel.  The hydrogen uptake in most storage materials strongly …

Towards a Neutron Microscope—A novel neutron lens based on reflection has recently been developed that could greatly benefit neutron imaging and other neutron scattering techniques.  

Pushing and Understanding the Limits of Spin-Exchange Optical Pumping of He-3—Neutron spin filters based on polarized 3He rely on the strong spin dependence of the absorption of neutrons by 3He gas.

Precision Measurement of Radiative Neutron Decay Branching Ratio and Energy Spectrum—Although neutron decay is typically considered as a three-body process, in the radiative correction it is always accompanied by inner-bremsstrahlung (IB) soft photons, n → e− + p + νe + γ.

Measurement of the Parity Non-Conserving Neutron Spin Rotation (PNC) in Liquid Helium—We recently completed a successful run of an experiment to study the strong interaction using weak interaction properties of the neutron. The neutron spin-rotation experiment is based on the …

Neutron Imaging for Advanced Catalyst Development and Durability Studies—Neutron imaging continues to play a key role in elucidating the role of water in proton exchange membrane fuel cells (PEMFCs) as highlighted by two projects with Los Alamos National Lab.  

Neutron Detector Replacement Program—The Department of Homeland Security/Domestic Nuclear Detection Office (DHS/DNDO) is pursuing a course to transform 3He alternative technologies into integrated systems which will lessen the demand …

Measurement of the Electron-Antineutrino Correlation in Neutron Decay—The angular correlation between the beta electron and antineutrino in nuclear beta decay α is the least well-known of the group of neutron decay observables that has been studied intensely …

Magnetically Trapped Neutron Lifetime Experiment—The decay of the free neutron is the simplest nuclear beta decay and is the prototype for all charged current semi-leptonic weak interactions.  The decay parameters, the neutron lifetime in …

High-Efficiency Neutron Detection and Spectroscopy—Precise knowledge of the fast neutron spectrum and fluencies is essential for several experimental endeavors requiring the low-background of the underground ground environment.

Californium Neutron Irradiation Facility—NIST provides an exposure facility for high neutron fluencies called the Californium Neutron irradiation Facility (CNIF).

Advanced Neutron Imaging Facility—The NIST Neutron Imaging Facility (NNIF) at the NIST Center for Neutron Research.

Precision Measurement of the Neutron-He3 Incoherent Scattering Length—The Neutron Interferometer and Optics Facility performed a precision measurement of the n-3He incoherent scattering length. Quantum chromodynamics describing the strong interaction between quarks …

Neutron Interferometry with Polarized Neutrons as an Additional Degree of Freedom—Our goal is to apply Quantum Information Processing techniques to improve neutron interferometry contrast by making our final measurement insensitive to crystal imperfections

X-ray Detection with Large Area Avalanche Photodiodes for the Neutron Radiative Decay Experiment—Operation of the second neutron radiative decay experiment has been completed.  In this experiment we observed the emission of photons that accompany neutron beta decay.

Continuous Spin-Exchange Optical Pumping in High Flux Neutron Beams—We collaborated on tests at the Insitut Laue Langevin (ILL) to study the effects of high flux neutron beams on spin-exchange optical pumping (SEOP).  The key result of this published work was the …

Alpha-gamma Counting for High Accuracy Fluence Measurements—Neutron fluence is measured by counting gamma-rays from the reaction n+10B®4He+7Li + g(478KeV) with a calibrated gamma detector. The gamma detector is calibrated in a multi-step procedure that uses …

A Novel Optical Technique for Rapid Detection of Neutrons—Almost every instrument at the NCNR and other neutron scattering facilities depends on 3He proportional tubes because of their high efficiency, good background rejection, and reliability.  New …

Neutron Imaging of Lithium and Alkaline Batteries—A common topic in energy systems is the need for in situ measurement of the mass transport of light ion species such as hydrogen or lithium.  Neutron imaging has played a critical role in the …

 
Contact

Arif 

Muhammad Arif, Group Leader

301-975-6303 Telephone
301-975-6200 Group Secretary
301-926-1604 Facsimile

100 Bureau Drive, M/S 8461
Gaithersburg, MD 20899-8461

Neutron Physics Staff Directory