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Physics

Radiation

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Displaying 51 - 75 of 268

Polarization Effects of X-ray Monochromators Modeled Using Dynamical Scattering Theory

July 1, 2021
Author(s)
Marcus Mendenhall, David R. Black, Donald Windover, James Cline
The difference in the diffracted intensity of the sigma-and pi-polarized components of an X-ray beam in powder diffraction has generally been treated according to equations based on dipole scattering, also known as kinematic X-ray scattering. Although this

A new measurement of the 122Sb half-life

June 5, 2021
Author(s)
Giancarlo D'Agostino, Marco Di Luzio, Nicholas Sharp, Massimo Oddone
Following significant discrepancies observed in rescaling collected 122Sb -peak count rates to a reference time by decay corrections, we looked at the literature supporting the presently recommended 2.7238(2) d 122Sb half-life value. The reading

Vectorizing Green's Identities

May 5, 2021
Author(s)
Alex Yuffa
Green's theorem and Green's identities are well-known and their uses span almost every branch of science and mathematics. In this paper, we derive a vector analogue of Green's three scalar identities and consider some of their uses. We also offer a number

Effects of Cathode Corrosion on Through-Plane Water Transport in Proton Exchange Membrane Fuel Cells

April 21, 2021
Author(s)
Daniel S. Hussey, Joseph Fairweather, Dusan Spernjak, Adam Weber, David Harvey, Silvia Wessell, David L. Jacobson, Kateryna Artyushkova, Rangachary Mukundan, Rodney Borup
The corrosion of carbon in the electrode supports of proton-exchange-membrane fuel cells leads to electrode collapse, reduced active catalyst area, and increased surface hydrophilicity. While these effects have been linked to performance degradation over

Neutron Imaging of Laser Melted SS316 Test Objects with Spatially Resolved Small Angle Neutron Scattering

April 21, 2021
Author(s)
Daniel S. Hussey, Adam J. Brooks, Caroline G. Lowery, Gerald L. Knapp, Bridget E. Cadigan, Shengmin Guo, Leslie G. Butler
A novel neutron far field interferometer is explored for sub-micron porosity detection in laser sintered SS316 test objects. The results shown are images and volumes of the first quantitative neutron dark-field tomography at various autocorrelation lengths

A new model dielectric function for loss functions and electron damping

March 10, 2021
Author(s)
Eric L. Shirley
Trends in the zeroth frequency moment of the imaginary part of the dielectric function are studied for a wide range of metals, semiconductors and insulators. These results are combined with estimates for the inverse-first moment (related by Kramers-Kronig

Ra-224 activity, half-life, and 241 keV gamma ray absolute emission intensity: a NIST-NPL bilateral comparison

December 31, 2020
Author(s)
Denis E. Bergeron, Sean Collins, Leticia Pibida, Jeffrey T. Cessna, Ryan P. Fitzgerald, Brian E. Zimmerman, Peter Ivanov, John Keightley, Elisa Napoli
The national metrology institutes for the United Kingdom and the United States have compared activity standards for 224Ra, an -particle emitter of interest as the basis for therapeutic radiopharmaceuticals. Solutions of 224RaCl2 were assayed by absolute

H2 Production in the 10B(n,?)7Li Reaction in Water

December 4, 2020
Author(s)
Alan K. Thompson, Travis C. Dietz, Mohamad Al-Sheikhly, Marcin Sterniczuk, David M. Bartels
We demonstrate a method for measuring the H2 produced in water from the 10B(n,α)7Li fission reaction. Low energy neutrons from the NIST Center for Neutron Research interact with borate- containing water in a temperature-controlled high pressure cell made

False Alarm Testing for Radiation Detection Systems

October 2, 2020
Author(s)
Dennis D. Leber, Leticia S. Pibida
An operator of a radiation detection system that displays a high rate of false alarms may be- come desensitized to these alarms. This action is known as alarm fatigue and can have detri- mental results as the operator may cease to respond to what may be

The Next Generation of Current Measurement for Ionization Chambers

September 1, 2020
Author(s)
Ryan P. Fitzgerald, Denis E. Bergeron, Dean G. Jarrett, Neil M. Zimmerman, Carine Michotte, Hansjoerg Scherer, Stephen Giblin, Steven Judge
Re-entrant ionization chambers (ICs) are essential to radionuclide metrology and nuclear medicine for maintaining standards and measuring half-lives. Metrology-quality systems must be precise and stable to 0.1% over many years, and linear from 10^(-14) A

Effect of Teflon(R) Transmittance on Sensitivity of Thermoluminescence Dosimeter Cards

May 20, 2020
Author(s)
Vyacheslav B. Podobedov, Carl C. Miller, Alexander Romanyukha, Andrew Hoy
Thermoluminescence dosimeter cards purchased by the United States Navy in recent years have different radiation sensitivities, e.g. they exhibit a different amount of light per dose unit. Presented tests indicate that the optical transparency of the Teflon

Non-fuel Antineutrino Contributions in the High Flux Isotope Reactor

May 14, 2020
Author(s)
PROSPECT COLLABORATION, Jerome LaRosa, Hans Pieter Mumm, Svetlana Nour, Mark Tyra, Denis E. Bergeron
Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties starting to surpass those from theory, it is important to carefully consider all sources of e in making theoretical predictions

Accurate Integral Counting Using Multi-channel Analyzers

May 1, 2020
Author(s)
Ryan P. Fitzgerald, Lynne E. King
Many techniques in radionuclide metrology rely on accurate measurement of the total count rate, that is integral counting, from a detector. In modern experiments, this can be achieved by integrating the total number of counts in an energy spectrum produced

Radiation damage of liquid electrolyte during focused X-ray beam photoelectron spectroscopy

April 12, 2020
Author(s)
Christopher M. Arble, Hongxuan Gou, Evgheni Strelcov, Brian D. Hoskins, Patrick Zeller, Matteo Amati, Luca Gregoratti, Andrei A. Kolmakov
Ambient pressure X-ray photoelectron spectroscopy (APXPS) has become an effective tool to interrogate chemical states at surfaces relevant to real operational conditions. Herein we employ a graphene-capped microvolume array sample platform for scanning

228Th breakthrough in 224Ra samples: what can we know and when can we know it?

April 6, 2020
Author(s)
Denis E. Bergeron, Ryan P. Fitzgerald, Leticia S. Pibida
Recent renewed interest in radium-224 (224Ra) as a radiotherapeutic agent prompted the development of a primary standard for activity at the National Institute of Standards and Technology (NIST). The 224Ra decay chain includes the emission four alpha

Low energy cross section measurement of the 10B(a;n)13N reaction and its impact on neutron production in 1st generation stars

February 26, 2020
Author(s)
Q Liu, M Febbraro, R.J. deBoer, S. Aguilar, A Boeltzig, Y Chen, M Couder, J Gorres, Jamie Weaver, K. T. Macon, M. Wiescher, K. Manukyan, L. Morales, S Pain, W. A. Peters, C. Seymour, G. Seymour, R. Toomey, B. Vande Kolk
Nucleosynthesis in the fi rst generation of massive stars offer a unique setting to explore the creation of the fi rst heavier nuclei in an environment free of impurities from earlier stellar generations. In later generations of massive stars, hydrogen

Optimum lithium loading of a liquid scintillator for neutron and neutrino detection

February 11, 2020
Author(s)
Hans Pieter Mumm, Denis E. Bergeron, Mark Tyra, Jerome LaRosa, Svetlana Nour, T.J. Langford, Dimitry A. Pushin
Neutral particle detection in high-background environments is greatly aided by the ability to easily load 6Li into liquid scintillators. We describe a readily available and inexpensive liquid scintillation cocktail stably loaded with up to 1 % Li by mass
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