View Generic Document: Development of a Bismuth Filter for the Filter Analyzer Neutron Spectrometer
Citation:
Zeitoun, Ramsey (2005). Development of a Bismuth Filter for the Filter Analyzer Neutron Spectrometer. National Institute of Standards and Technology, Technology Administration, U.S. Department of Commerce..
The neutron is a novel and powerful probe of condensed matter. It possesses no charge and interacts with atoms via nuclear rather than electrical forces, thus allowing it to
penetrate through most materials. The wavelike properties of the neutron permits one to utilize diffraction methods to create beams of monoenergetic neutrons for use in such scattering techniques
as neutron vibrational spectroscopy (NVS). NVS is analogous to photon-based vibrational spectroscopies such as infrared or Raman spectroscopy, but possesses unique properties that render it
complementary to these spectroscopies and invaluable for probing the vibrational spectra of solid-state materials. One limitation of the Filter-Analyzer Neutron Spectrometer (FANS), the world-class
NVS instrument at the NIST Center for Neutron Research (NCNR), is the presence of spurious low-level background scattering from the beryllium (Be) filter used in the scattered-neutron analyzer.
Such spurious scattering complicates the clean measurement of the vibrational density of states of more weakly scattering samples. Here, it is determined that these spurious scattering can be
eliminated by an additional “polycrystalline” bismuth (Bi) filter placed in front of the Be filter. The development of a Bi filter with sufficient polycrystallinity is nontrivial since bismuth
tends to form unacceptably large crystallites upon solidification from the melt. To substantiate this discovery, diverse bismuth samples were studied using the SANS (Small Angle Neutron Scattering)
instrument, and DCS (Disk Chopper Spectrometer) in order to characterize the neutron transmission of the samples. Metallurgical studies were also extensively sought after for characterization and
information into ways to most appropriately optimize neutron transmission. With a prototype of the filter in place, and plans for creating the final one underway, low scattering samples such as
dodecacalcium 14-aluminum oxide were analyzed and studied without fear of spurious scattering and false readings.
Publisher
National Institute of Standards and Technology, Technology Administration, U.S. Department of Commerce.
Date
2005-01-01
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Additional Notes
Contract grant sponsor: National Institute of Standards and Technology; contract grant number: 70NANB4H1049; Citation: SURF student 2004 abstracts. In SURF Colloquium 2004.
http://www.surf.nist.gov/respr.htm; Description: A presentation in the 2004 National Institute of Standards and Technology (NIST) - Material Science and Engineering Laboratory (MSEL) - National
Science Foundation (NSF) Summer Undergraduate Research Fellowship (SURF) program (http://www.surf.nist.gov/surf2.htm) for students majoring in science, mathematics and
engineering.
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View Generic Document: Development of a Bismuth Filter for the Filter Analyzer Neutron Spectrometer 