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COMPRES Fifth Annual Meeting

COMPRES Neutron Initiative:. Identify and broaden the EAR neutron scattering community in the U.S. Stimulate and promote the use of neutron scattering in the Earth Sciences. Support educational activities

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COMPRES Fifth Annual Meeting

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  1. COMPRES Neutron Initiative: • Identify and broaden the EAR neutron scattering community in the U.S. • Stimulate and promote the use of neutron scattering in the Earth Sciences. • Support educational activities • Identify needs of the community, including future requirements for instrumentation and sources COMPRES Fifth Annual Meeting

  2. sitepu@vt.edu COMPRES Neutron Initiative: • Financial assistance to carry out neutron scattering experiments and/or to participate in workshops and conferences on neutron scattering • H. Sitepu: design and carry out high-P,T neutron experiments • Build user community by assisting members of community with experiments • Community informed about upcoming neutron workshops, conferences, deadlines for proposals, etc. • Education materials available on www.vt.edu/compres COMPRES Fourth Annual Meeting

  3. Recent projects: • “High-pressure neutron diffraction study of AlOOD” (ISIS) - C. Vanpeteghem, H. Sitepu (VT) and E. Ohtani, S. Asami • “Feasibility high pressure study of lithium aluminum deuteride [LiAlD4] and calcite [CaCO3]” using a PE cell on HIPD at LANSCE – H. Sitepu, A. Llobet Megias, and Y. Zhao • “Investigation of Mg-Al site disorder in shocked MgAl2O4 spinel using neutron diffraction“ (ISIS) O. Tschauner (UNLV), H. Sitepu (VT), P. Asimow and T.J. Ahrens (Cal Tech). • “Quantitative texture analysis of deformed natural quartz vein from the Torridon area of NW Scotland using neutron diffraction” (FRM-II) R.D. Law (VT), H. Sitepu (VT) and Prof. H.-G. Brokmeier (Tech. Univ. Clausthal). • “Compressibility of layered molybdite (MoO3) powders determine from neutron diffraction studies at high pressure” (LLB) H. Sitepu (VT) and Dr. I. Goncharenko (LLB). COMPRES Fourth Annual Meeting

  4. Neutron Initiative in Compres II? • Travel support will continue – to be administered by COMPRES Central • Form high-pressure neutron “task-force” made up members of the COMPRES community, experienced neutron researchers and representatives from neutron facilities (i) form high-pressure neutron network for exchange of information between high-pressure neutron facilities within the United States (LANSCE, IPNS, HIFR, SNS) and from around the world (ISIS, ILL, J-PARC) (ii) identify community needs and nurture infrastructure development projects and / or grand challenges as (iii) target, where appropriate, additional resources through which to leverage COMPRES funds

  5. New projects such as . . . • Temperature measurement using neutron reasonance spectroscopy (synergy with high P-T calibration effort) • Software development for on-line / off-line evaluation and processing of data (synergy with CEAD) M. Dove, Y. Le Godec, S.A.T. Redfern, W.G. Marshall, H.J. Stone, M.G. Tucker,

  6. 2 0 0 m m High P-T cells for community? • Paris-Edinburgh cell • Modified P-E cell with belt design (Dobson, 2005) • Panoramic cell • or ???

  7. MSA Short Course:NEUTRON SCATTERING IN EARTH SCIENCES • December 7th and 8th, 2006 http://www.minsocam.org/msa/sc/

  8. Temperature measurement by radiography Transmitted intensity Neutron Absorption resonance Wavelength Transmitted neutron beam Incoming neutron beam Detector Sample in two sections Thin foil

  9. Effect of temperature Width of resonance line increases with temperature due to Doppler effect Transmitted intensity Wavelength Width of resonance line can be used to calibrate temperature

  10. Doppler Broadening of Absorption Resonances: 181Ta (early data) 181Ta 10.36eV resonance Room temperature 181Ta 10.36eV resonance 1400°C

  11. Measured neutron resonance lineshape Breit-Wigner lineshape Energy transfer function (the Doppler broadening function) Total cross-section: Transmitted signal: Area density of absorbing nuclei Detected signal: Instrument resolution function Pulse source function Detector efficiency

  12. Example resonance absorption specta

  13. Doppler Broadening of Absorption Resonances - Theory • The resonance lineshape for a stationary nuclei is well described by the single-level Breit-Wigner equation • Must account for the thermal motion of the nuclei in the lab frame (energy transfer function) • For a free gas or classical solid assume a Maxwellian distribution of velocities • For weak lattice binding can treat as a free gas replacing T by Teff where For an Einstein solid:

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