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Titel |
New Perspectives for In-Situ Rock Deformation and Recrystallisation Analysis - POWTEX Neutron Diffractometer at FRM II Garching, Germany |
VerfasserIn |
Jens M. Walter, Christian Randau, Michael Stipp, Bernd Leiss, Klaus Ullemeyer, Helmut Klein, Bent T. Hansen, Werner F. Kuhs |
Konferenz |
EGU General Assembly 2013
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 15 (2013) |
Datensatznummer |
250082763
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Zusammenfassung |
For the investigation of fabric development in mono- and polyphase rocks and their
deformation kinematics the quantitative analysis of the crystallographic preferred orientation
(CPO) is a common tool. Furthermore, bulk texture measurements also allow the quantitative
characterisation of the anisotropic physical properties of rocks. As neutrons have large
penetration capabilities of several cm in geological sample materials neutron diffraction is a
strong tool for geoscientific texture analysis.
The new POWTEX (POWder and TEXture) Diffractometer at the neutron research reactor
FRM II in Garching, Germany is designed as a high-intensity (~1 x 107 n/cm2s)
time-of-flight diffractometer. The combination of high flux, the utilization of wavelength
frames (TOF) and the large detector coverage ( 9.8 sr) allow fast and effective texture
measurements. As the cylindrical detector provides sufficient angular resolution also for
sharp recrystallisation textures, POWTEX offers unique possibilities for in-situ
time-resolved texture measurements during deformation and recrystallisation experiments
on rock materials as large sample environments can be placed inside the detector
system.
The in-situ deformation apparatus is a new design to minimize shadowing effects inside the
cylindrical detector and is operated by a uniaxial spindle drive with a maximum axial load of
250 kN. The HT deformation experiments will be carried out in uniaxial compression or
extension and an upgrade to triaxial deformation conditions is envisaged. The apparatus can
alternatively be used for ice deformation by inserting a cryostat cell for temperatures down to
77 K with a triaxial apparatus allowing also simple shear experiments. Strain rates range
between 10-8 and 10-3 s-1 reaching to at least 50 % axial strain. The deformation
apparatus is designed for continuous long-term deformation experiments and can be
exchanged between in-situ and ex-situ placements during continuous operation
inside and outside the neutron detector. For the in-situ recrystallisation analysis
the specially designed rotatable furnace reaches temperatures of up to 1800° C
and allows a quantitative 3D analysis of the recrystallisation by the stereological
calculation of the measured textures as shown by Klein et al. 2009 for synchrotron
experiments.
References:
Klein, H. (2009). Principles of highly resolved determination of texture and microstructure
using high-energy synchrotron radiation. Adv. Eng. Mat. 11, 452-458. |
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