Neutron Diffraction Studies at the IBR2 Reactor

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Neutron Diffraction Studies at the IBR2 Reactor

• Status and Future

J.H. Behrmann
Geologisches Institut, Universität Freiburg,
Albertstr. 23b, 79104 Freiburg, Germany
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Status and Future

• Experimental facilities available
• Possible ventures into new equipment
• Examples of current studies
• Future experimental activities

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SKAT - Neutron texture diffractometer
Experimental facilities
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Parameters of SKAT
Total flight path (moderator detector) 103.81 m
Range of wavelengths ? 0.8 7.6 Å
Range of d-spacings 0.6 5.6 Å
Detectors up to 21 3He single tube, Ø 60mm, unique scattering angle 2Q90
Collimators two sets of Gd-coated soller collimators, angular dispersion 18 and 45, cross section 55 x 55 mm
Resolution Dd/d 0.55 at d 2 Å(18 collimation) 0.7 at d 2 Å (45 collimation)
Beam cross section 50 x 85 mm
Typical sample volume 20 50 cm3
Experiment control VME-based measuring system running OS-9 and X WINDOW
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Main advantages of SKAT

• low absorption of neutrons in matter large
  sample volumes accessible
• TOF complete diffraction patterns can be
  recorded
• application of multiple detectors measurements
  are fast
• excellent spectral resolution suitable for
  polyphase geological samples with many
  diffraction lines
• unique scattering angle 2? of all detectors
  minimum of intensity corrections required

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Polyphase rock sample calcite quartz /-
dolomite
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EPSILON -
Experimental facilities
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Parameters of EPSILON
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Main advantages of EPSILON

• Excellent spectral resolution because of long
  flight path (gt 100 m)
• Intensity gain by operation of radial collimators
  and multi-detector system
• Simultaneous detection of nine different
  directions on Debye-Scherrer cone offers
  possibility for strain tensor estimations
• Detection of lattice strains by Bragg peak shift
  and broadening
• Uniaxial pressure device (max. load 150 MPa) for
  in situ deformation of samples
• Laser extensometer for in-situ determination of
  macroscopic sample strain
• Temp. cabin for thermal stability (DT /- 0.5 K)

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Possible ventures into new equipment

• Construct new neutron guide (curved)
• Achieve approx. 10x increase in available
  proportion of thermal neutrons

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Examples of current studies
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Anisotropic thermal expansion of
rocks/minerals,Fabric destruction of building
stones by weathering
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Bent marble facade panels
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Compressional wave velocity anisotropy in rocks
quartz single crystals
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Texture-related compressional wave anisotropy in
Quartzites, Naxos Island, Greece
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Comparison of texture-inducedand
microcrack-induced Vp anisotropy
Texture-induced, quartzite, Naxos
microcrack-induced, quartz-rich gneiss, Austrian
Alps
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Studies of relation between textures and acoustic
anisotropy are vital for the understanding of
seismic reflectors in the deep Earths crust
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Residual lattice strains in crystals and rocks
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Bragg peak shift as residual lattice strain
indicator
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Future experimental activities

• Future projects should either contain a component
  of instrument development, to be carried out when
  reactor is being reconstructed
• or have close relation to measurement of other
  physical properties of geo-materials (elastic,
  plastic, magnetic, thermal, strain state), not
  using neutron radiation
• or address fundamental questions in applied
  geo-materials research
• or emphasize on development of novel methods of
  data analysis

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Expressions of interest

• Rock anisotropy
• elastic (Behrmann, Freiburg Kern, Kiel
  Nikitin/Ivankina, Dubna)
• thermal (Siegesmund, Göttingen)
• magnetic (de Wall, Würzburg)
• strain state (Frischbutter, Potsdam)
• Texture for kinematic analysis
• (Kroner, Freiberg Behrmann, Freiburg)
• Mathematical background (Schaeben, Freiberg
  Nikolayev, Dubna)