Brillouin Scattering With Simultaneous XRay Diffraction at GSECARS, Advanced Photon Source: Toward D

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Brillouin Scattering With Simultaneous X-Ray
Diffraction at GSECARS, Advanced Photon Source
Toward Determination of Absolute Pressure Scales

• Jay Bass1
• Stanislav Sinogeikin1,2
• Dmitry Lakshtanov1
• Carmen Sanchez-Valle1
• Vitali Prakapenka2,
• Guoyin Shen2,3
• Jean-Philippe Perrillat1
• Jingyun Wang1
• Bin Chen1
• 1 University of Illinois at UC, Geology Dept.
• 2 GSECARS, The University of Chicago
• 3 HPCAT, Advanced Photon Sourse, Argonne National
  Laboratory
• 4 Carnegie Institution of Washington, Geophysical
  Laboratory

Fall AGU 2006
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Brillouin Scattering with synchrotron X-rays at
the APS Elasticity Grand Challenge COMPRES
Infrastructure Development Project
Measure sound velocities and density
simultaneously
Absolute or internally consistent Pressure
Scales Zha et al., Brillouin on MgO (PNAS, 2000)
Isothermal bulk modulus (volume measurements)
Adiabatic elastic moduli (velocity measurements)
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Phase Transitions Stishovite - CaCl2
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Stishovite - CaCl2 Brillouin scattering
velocities
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Brillouin scattering

• Acoustic waves present in a solid due to thermal
  motion of atoms
• Laser light interacts with phonons (or density /
  refractive index fluctuations) and is scattered
  with Doppler shifted frequency ??
• Brillouin shift is proportional to acoustic
  velocity
• Vi ??? / 2nsin (?/2)

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Schematic diagram of the Brillouin system
installed at sector 13-BMD (GSECARS) at APS
Sinogeikin et al.,Rev. Sci. Instr. 77, 2006
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Schematic diagram of the Brillouin system
installed at sector 13-BMD at APS (Lower Tier)
Motorized translation components (controllable
from outside the hatch, blue boxes) HMTS -
horizontal motorized translation stage VMTS -
vertical motorized translation stage MLFA -
motorized laser focusing assembly MSCA -
motorized signal collecting assembly SPOA -
sample positioning and orientation assembly
SL-LB - sample light / light block. Observation /
feedback elements (red boxes) VC - video camera
BT - beam target. X-ray components MAR - MAR
Imaging plate XBS - X-ray beam stop CS -
cleanup slit.
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Mobile focusing/collecting part of the Brillouin
system at 13-BMD GSECARS
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X-ray image and integrated spectrum of
single-crystal NaCl at ambient conditions
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Single crystal NaCl (B1) at 30 GPa in DAC in Ne
pressure medium
Schematic view of simultaneous Brillouin
scattering and X-ray diffraction in DAC
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X-ray image and spectrum of single-crystal NaCl
in Ne at 30 GPa
NaCl (B1) (200)
Ne
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Single crystal Brillouin spectrum of NaCl (B1)
and velocity distribution in (100) plane at 30.5
GPa
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Single crystal and aggregate elastic moduli of
NaCl (B1) as a function of density
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Anisotropy of NaCl (B1) to 30 GPa
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Aggregate velocities of NaCl (B1) as a function
of density
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Absolute equations of state / pressure scale
Isothermal bulk modulus (volume measurements)
Adiabatic elastic moduli (velocity measurements)
We measure Ks as a function of volume directly.
The problem is to convert KS to KT at high
pressure, e.g. we need to know volume dependence
of a and g. Possible models/assumptions
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Conclusions

• We simultaneously measured single crystal (and
  aggregate) elastic moduli of NaCl (B1) with
  Brillouin spectroscopy and density with angle
  dispersive X-ray diffraction to 30.5 GPa.
• At high pressure NaCl exhibits extreme elastic
  anisotropy, which is gt3 times higher than that at
  ambient conditions.
• Above 17 GPa on approaching B1-B2 phase
  transition NaCl exhibits acoustic mode softening.
  
• Above 17 GPa the density velocity relations
  deviate from linearity and violate Birchs law.
• Acoustic softening indicates that B1-B2 phase
  transition in NaCl may be multi-step and of more
  complicated nature than it was previously
  thought.
• Pressure calculated from measured bulk modulus
  and density is higher than that calculated from
  Decker EOS by 3-5 at 30 GPa.

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Acknowledgments

• NSF Elasticity Grand Challenge
• COMPRES Infrastructure development project
• GSECARS Sector 13, Advanced Photon Source