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Neutron research

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Displaying 776 - 800 of 914

An experiment for the precision measurement of the radiative decay mode of the neutron

October 5, 2009
Author(s)
R Cooper, Christopher D. Bass, E Beise, H Breuer, Jim Byrne, T E. Chupp, Kevin Coakley, Maynard S. Dewey, B Fisher, Changbo Fu, Thomas R. Gentile, M. McGonagle, Hans Pieter Mumm, Jeffrey S. Nico, Alan Keith Thompson, F E. Wietfeldt
The neutron typically beta decays into a proton, electron, and antineutrino. In some decays, it can be accompanied by a high energy photon. We recently performed the rst observation of the radiative beta decay branch for the free neutron with photons of

Effects of high intensity neutron flux on in-situ spin-exchange optical pumping of He-3

September 17, 2009
Author(s)
Thomas R. Gentile, E Babcock, Stephen Boag, C. Becham, T E. Chupp, Gordon L. Jones, A K. Petukhov, T G. Walker
Prior studies revealed neutron beam-induced alkali-metal spin relaxation in 3He cells polarized in-situ by spin-exchange optical pumping. These effects are minor for neutron beams of low to moderate intensity, but become important at the highest neutron

Glassy Carbon as an Absolute Intensity Calibration Standard for Small Angle Scattering

August 19, 2009
Author(s)
Andrew J. Allen, Jan Ilavsky, Fan Zhang, Gabrielle G. Long, Pete R. Jemian
Absolute calibration of small-angle scattering (SAS) intensity data (in units of differential cross-section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number

Application of Thermal Gradients to Achieve Orientational Order in Block Copolymer Thin Films

August 18, 2009
Author(s)
Nathaniel J. Fredin, Brian Berry, Kevin G. Yager, Alamgir Karim, Sushil K. Satija, Deanna Pickel, Ronald L. Jones
The development of methods that permit control over the long-range order and orientation of microdomains in block copolymer (BCP) thin films for bottom-up approaches to nanoscale surface patterning is of great interest for many applications, including

Coupled magnetic and ferroelectric hysteresis in multiferroic Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^

August 18, 2009
Author(s)
I. Cabrera, M. Kenzelmann, Wangchun Chen, Ross Erwin, Thomas R. Gentile, Juscelino Leao, Jeffrey W. Lynn, N. Rogado, R. J. Cava, C. Broholm, G. Lawes, Ying Chen
Electric control of spin chirality in a magnetically frustrated multiferroic is demonstrated through polarized magnetic neutron diffraction. Cooling to the cycloidal multiferroic phase of Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^ in an electric field causes the

Anomalous thermal behavior in microcalorimeter gamma-ray detectors

July 20, 2009
Author(s)
Robert D. Horansky, James A. Beall, Kent D. Irwin, Joel N. Ullom
Improving the resolution of gamma-ray detectors is important for many fields, including determinations of the Lamb shift in atoms with high atomic numbers , nuclear treaty verification , and environmental monitoring. High-purity germanium detectors are

Combinatorial Study of Thin Film Metal Hydride by Prompt Gamma Activation Analysis

June 19, 2009
Author(s)
Raymond Cao, Jason Hattrick-Simpers, Richard Bindel, Bryan E. Tomlin, Rolf L. Zeisler, Rick L. Paul, Leonid A. Bendersky, Robert G. Downing
Cold neutron prompt gamma activation analysis (PGAA) was used to determine the amount of hydrogen in thin film Mg hydrides with varying hydrogenation times. The results suggest that the hydrogenation in the Mg thin films remains unsaturated even after 48

Phonon softening and anomalous mode near the x c = 0.5 quantum critical point inCa 2-x Sr x RuO 4

May 4, 2009
Author(s)
R. G. Moore, M. D. Lumsden, M. B. Stone, Jiandi Zhang, Ying Chen, Jeffrey Lynn, R. Jin, D Mandrus, E. W. Plummer
Inelastic neutron scattering is used to measure the temperature-dependent phonon dispersion in Ca2−xSrxRuO4(x=0.4,0.6). The in-plane Σ4 octahedral tilt mode softens significantly at the zone boundary of the high-temperature tetragonal (HTT) I41/acd

Itinerant spin excitations near the hidden order transition in URu2Si2

April 22, 2009
Author(s)
J. A. Janik, H. D. Zhou, Y.-J. Jo, L. Balicas, G. J. MacDougall, G. M. Luke, J. D. Garrett, K. J. McClellan, E. D. Bauer, J. L. Sarrao, Yiming Qiu, John R. Copley, Z. Yamani, W. J. Buyers, C. R. Wiebe
By means of neutron scattering we show that the high-temperature precursor to the hidden order state of the heavy fermion superconductor URu 2Si 2 exhibits heavily damped incommensurate paramagnons whose strong energy dispersion is very similar to that of

Measuring 6LI(N,T) and 10B(N,A) Cross Sections Using the NIST Alpha-Gamma Device

April 15, 2009
Author(s)
Maynard S. Dewey, David M. Gilliam, Jeffrey S. Nico, G.L. Green, A. Laptev, A. Yue
The 6LI(N,T) and 10B(N,A) cross sections are important neutron cross section standards. Precise knowledge of these cross sections is essential because they are often used as reference standards for obtaining the neutron fluence in investigations of the

A New Evaluation of the Half-life of 241Pu

April 14, 2009
Author(s)
Roger Wellum, Andre Verbruggen, Ruediger Kessel
A new evaluation of the half-life of 241Pu has been made by developing earlier methods and techniques and employing further measurements of the isotopic ratio of an initially enriched 241Pu material. A correction to the previous value has had to be made

International NMR-based Environmental Metabolomics Intercomparison Exercise

April 7, 2009
Author(s)
Daniel W. Bearden, Mark Viant, Jacob Bundy, Ian Burton, Tim Collette, Drew Ekman, Tobias Karakach, Ching Y. Lin, Simone Rochfort, Jeff de Ropp, Quincy Teng, Ron Tjeerdema, John Walter, Huifeng Wu
Several fundamental requirements must be met so that NMR-based metabolomics can be formally adopted into environmental monitoring and chemical risk assessment. Here we report an intercomparison exercise which has evaluated the accuracy, precision and

Quasielastic neutron scattering study of hydrogen motion in NbC(0.71)H(0.28)

March 30, 2009
Author(s)
Terrence J. Udovic, Jeremy Cook, Alexander Skripov, Reinhard Hempelmann, Andrey Rempel, Aleksandr Gusev
In order to study the mechanism and parameters of H jump motion in the nonstoichiometric Nb carbides, we have performed quasielastic neutron scattering (QENS) measurements for NbC(0.71)H(0.28) over the temperature range 11- 475 K. Our results indicate that

Use of Neutron Imaging for PEMFC Performance Analysis and Design

March 1, 2009
Author(s)
T Trabold, Jon P. Owejan, Jeffrey J. Gagliardo, David L. Jacobson, Daniel S. Hussey, Muhammad D. Arif
Efficient water management is one of the key design objectives for proton exchange membrane fuel cells (PEMFCs), due to the influence of water on material selection, hardware configuration, and stack operating conditions. Neutron imaging has proven to be

Study of hydrogen diffusion in superprotonic ionic conductors, MHXO4, by m+SR and QENS

February 21, 2009
Author(s)
Yutaka Ikedo, Hiroshi Nozaki, Masashi Harada, Jun Sugiyama, Taku J. Sato, Yasumitsu Matsuo, Kusuo Nishiyama, James S. Lord, Yiming Qiu, John R. Copley
In order to clarify the mechanism of high proton conductivity (σH+) for superprotonic ionic conductors, MHXO4, where M=Cs and Rb, X=S and Se, muon-spin rotation and relaxation (μ+SR) and quasi-elastic neutron scattering (QENS) measurements have been

Surface Dynamics of "Dry" Homopolymer Brushes

February 10, 2009
Author(s)
Bulent Akgun, Gokce Ugur, Jianqiang Zhang, Suresh Narayanan, Sanghoon Song, Heegu Lee, William J. Brittain, Hyunjung G. Kim, Sunil K. Sinha, Mark Foster
The dynamics of the surface height fluctuations on layers of covalently tethered, nearly monodisperse polymer chains synthesized by atom transfer radical polymerization were studied using x-ray photon correlation spectroscopy. The data reveal that both

Pulse Shape Discrimination for a Fast Neutron Detector

February 9, 2009
Author(s)
Kevin J. Coakley, Dominic F. Vecchia, Jeffrey S. Nico, B Fisher
We are developing a detector that uses liquid scintillator loaded with Li-6 for the efficient measurement of fast neutrons and their energy. Such a detector would have both scientific applications such as quantification of neutron energy spectra in

Radiative Beta Decay of the Free Neutron

February 2, 2009
Author(s)
R L. Cooper, T E. Chupp, Maynard S. Dewey, Thomas R. Gentile, Hans Pieter Mumm, Jeffrey S. Nico, Alan Keith Thompson, B M. Fisher, I Kremsky, F E. Wietfeldt, E J. Beise, H Breuer, K G. Kiriluk, J Bryne, Kevin Coakley, Changbo Fu
The theory of quantum electrodynamics predicts that the beta decay of the neutron into a proton, electron, and antineutrino is accompanied by a continuous spectrum of emitted photons described as inner bremsstrahlung. While this phenomenon has been
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