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Search Publications by: Wangchun Chen (Fed)

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Displaying 26 - 42 of 42

A 3He beam stop for minimizing gamma-ray and fast-neutron background

August 6, 2016
Author(s)
Danyal J. Turkoglu, Robert G. Downing, Wangchun Chen, Dagistan Sahin, Jeremy C. Cook
Prompt gamma-ray activation analysis facilities with high neutron currents (≥109 s-1) generate triton-induced fast neutrons from 6Li-loaded collimators and beam stops at rates that soon damage gamma-ray detectors. We develop an alternative beam stop design

A New Cold Neutron Imaging Instrument at NIST

July 6, 2015
Author(s)
Daniel S. Hussey, Christoph W. Brocker, David L. Jacobson, Thomas R. Gentile, Wangchun Chen, Elias M. Baltic, DV Baxter, J. Doskow, Muhammad D. Arif
The NIST neutron imaging program will build a new imaging instrument in the NCNR guide hall at the end of the neutron guide NG-6, beginning operation in summer of 2014. The NG-6 guide has a spectrum that is strongly peaked at a neutron wavelength of 5 Å

3 He Spin Filter Based Polarized Neutron Capability at the NIST Center for Neutron Research

July 24, 2014
Author(s)
WangChun Chen, Thomas R. Gentile, Ross W. Erwin, Shannon Watson, Qiang NMN Ye, Kathryn L. Krycka, Brian B. Maranville
A 3He neutron spin filter (NSF) program for polarized neutron scattering was launched in 2006 as part of the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) Expansion Initiative. The goal of the project was to

On the limits of spin-exchange optical pumping of 3He

July 2, 2014
Author(s)
Thomas R. Gentile, T G. Walker, E Babcock, Qiang NMN Ye, Wangchun Chen
Using diode bar lasers spectrally narrowed with chirped volume holographic gratings (VHGs), we have obtained an improvement in the 3He polarization achievable by spin-exchange optical pumping (SEOP). As compared to our past results with lasers narrowed

Wide Angle Polarization Analysis with Neutron Spin Filters

April 29, 2013
Author(s)
Qiang NMN Ye, Thomas R. Gentile, Jeffrey R. Anderson, Collin L. Broholm, WangChun Chen, Z DeLand, Ross W. Erwin, C. B. Fu, John E. Fuller III, Aaron V. Kirchhoff, J. A. Rodriguez-Rivera, V. Thampy, T G. Walker, Shannon Watson
We report substantial improvements in a compact wide angle neutron spin filter system that was recently employed on the Multi-Axis Crystal Spectrometer at the Center for Neutron Research at the U.S. National Institute of Standards and Technology. The

Friedel-like Oscillations from Interstitial Iron in Superconducting Fe 1+y Te 0.62 Se 0.38

March 7, 2012
Author(s)
V. Thampy, J. Kang, Jose Rodriguez Rivera, W. Bao, A. T. Savici, J. Hu, T. J. Liu, B. Qian, D. Fobes, Z. Q. Mao, C. B. Fu, Wangchun Chen, Q. Ye, Ross Erwin, Thomas R. Gentile, Z. Tesanovic, Collin L. Broholm
Using polarized and unpolarized neutron scattering we show that interstital Fe in superconducting Fe 1=yTe 1-xSe x induces a magnetic Friedel-like oscillation that idffracts at Q = (1⁄20) and involves greater than}50 neighboring Fe sites. The interstitial

Local Weak Ferromagnetism in Single-Crystalline Ferroelectric BiFeO 3

November 1, 2011
Author(s)
M. Ramazanoglu, M. Laver, William D. Ratcliff, Shannon M. Watson, Wangchun Chen, Andrew Jackson, Karunakar NMN Kothapalli, Seongsu Lee, S.- W. Cheong, V. Kiryukhin
Polarized small-angle neutron scattering studies of single-crystalline multiferroic BefeO 3 reveal a long-wavelength spin density wave generated by 1° spin canting of the spins out of the rotation plane of the antiferromagnetic cycloidal order. This

Nanometer Size Magnetic Domains and Coherent Magnetization Reversal in a Giant Exchange Bias System

August 23, 2011
Author(s)
C. Dufour, M .R. Fitzsimmons, Julie Borchers, M. Laver, Kathryn L. Krycka, K. Dumesnil, Shannon M. Watson, Wangchun Chen, S. Singh
We present compelling evidence obtained with small angle scattering of unpolarized and polarized neutron beams the magnetization reversal occurs via formation of 10-100's nm sized magnetic domains in an exchanged biased DyFe 2/YFed2^ superlattice. The

Polarized He-3 cell development and application at NIST

June 14, 2011
Author(s)
Thomas R. Gentile, WangChun Chen, Changbo Fu, Shannon Watson, Gordon L. Jones, J. W. McIver, D. R. Rich
Over a period of well over a decade, a large number and variety of polarized 3He cells for neutron applications have been developed and tested at the U.S. National Institute of Standards and Technology (NIST). These cells have primarily been employed for

In-situ Polarized He3-Based Neutron Polarization Analyzer for SNS Magnetism Reflectometer

January 31, 2011
Author(s)
W-T Lee, X Tong, J. Pierce, M. Fleenor, A. Ismaili, JL Robertson, Wangchun Chen, Thomas R. Gentile, A. Hailemariam, R J. Goyette, A. Parizzi, V Lauter, F. Klose, H. Kaiser, C. Lavelle, DV Baxter, G L. Jones, J. Wexler, L. McCollum
We report here the construction and neutron transmission test results of an in-situ polarized 3He-based neutron polarization analyzer system for the Magnetism Reflectometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The analyzer uses

A Wide Angle Neutron Spin Filter System Using Polarized 3He

October 16, 2010
Author(s)
Changbo Fu, Thomas R. Gentile, Wangchun Chen, Ross Erwin, Shannon M. Watson, Collin L. Broholm, Jose Rodriguez Rivera, Julia Scherschligt, G L. Jones
Polarized 3He neutron spin filters can operate over a wide neutron energy range and provide a large angular acceptance. A compact 3He neutron spin filter system has been developed for the Multi Axis Crystal Spectrometer at the NIST Center for Neutron

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

Spin-exchange Optical Pumping of 3He with Rb/K Mixtures and Pure K

December 31, 2007
Author(s)
Wangchun Chen, Thomas R. Gentile, S E. Babcock, T G. Walker
We have studied the efficiency of spin-exchange optical pumping (SEOP) in cells that contain either pure rubidium, mixtures of rubidium and potassium, or pure potassium. Optical pumping was performed with spectrally narrowed diode array lasers operating at