Online Brillouin spectroscopy at GSECARS

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On-line Brillouin spectroscopy at GSECARS
Vitali B. Prakapenka, Mark L. Rivers, Stephen R.
Sutton, Alexei Kuznetsov - University of
Chicago Jay Bass, Stanislav V. Sinogeikin ,
Dmitry Lakshtanov UIUC, now at HP-CAT Bob
Liebermann - COMPRES
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Brillouin scattering
Acoustic waves present in a solid due to thermal
motion of atoms
In symmetric platelet geometry the Brillouin
shift is directly proportional to acoustic
velocity
Laser light interacts with phonons (or density /
refractive index fluctuations) and is scattered
with Doppler shifted frequency ??
Vi ??? / 2sin (?/2)
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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Brillouin spectroscopy

• Advantages
• direct measurements of acoustic velocities
• nondestructive optical spectroscopy
• very small samples (down to 10-20 ?m)
• from single crystal to non-crystalline materials
• measurements at P-T conditions of the Lower
  Mantle
• Disadvantages
• complicated optical system
• transparent and translucent samples
• elastic moduli only for known density

Shear ??V2S
Bulk KS?V2P - 4/3 ?,
Single-crystal C11 ?Vp2(100)
Rev. Sci. Instrum. 77, 103905 2006
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Why do we need Brillouin spectroscopy on-line?

• measuring sound velocities and densities of
  materials simultaneously results in a pressure
  scale without reference marker and important
  materials properties (equations of state,
  elasticity, etc) as a function of pressure and
  temperature
• the experimental data collected with XRD and BS
  at the same pressure-temperature conditions
  provide information essential for comparing with
  seismic observations and modelling the
  composition and evolution of the Earth
• Brillouin spectroscopy combined with XRD open a
  new area of in-situ studies of materials at
  extreme conditions

S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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Key design considerations

• should be flexible respect to the sample position
  and compatible with x-ray diffraction technique
• should be compact system due to limited space in
  the beamline station
• should not interfere with other experimental
  techniques that are performed on the beamline
  (EXAFS, CMT, LVP)
• should have reliable and quick alignment
  procedure
• should have remote control option for data
  collection, adjustment and monitoring outside of
  hutch
• should satisfy laser safety requirements due to
  using class-IV laser

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• an elevated optical table
• vertical scattering plane
• movable along optical axis

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S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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Calibration Brillouin system with MgO single
crystal starting with 100 direction at ambient
conditions
collection time is 5 minutes
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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EPICS control
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XRD and BS of single crystal MgO in 100
direction in the DAC at 4 GPa
MEW
MgO Vp
MgO Vs
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka,
Rev. Sci. Instrum. 77, 103905 2006
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XRD and BS of polycrystalline NaCl at 35 GPa
collected simultaneously
NaCl Vp
NaCl Vp
Diamond Vs
Diamond Vs
NaCl Vs
NaCl Vs
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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High Temperature experiments
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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Temperature control(slow feedback)
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka,
Rev. Sci. Instrum. 77, 103905 2006
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XRD and BS of MgO in 100 direction in the DAC
at 8 GPa and 800 K
Ar BS
Ar BS
Ar Vp
Ar Vp
MgO Vp
MgO Vp
MgO Vs
MgO Vs
Ar pressure medium is melted collection time 10
minutes
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In situ XRD and BS of argon at 60 GPa and 700 K
S. V. Sinogeikin, J. D. Bass, V.B. Prakapenka et
al, Rev. Sci. Instrum. 77, 103905 2006
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Last year improvements

• Gear boxes (125) to improve accuracy of sample
  and laser beam positioning
• Two horizontal translation stages for microscope
  alignment
• Video switch system with multiple cameras (16)
  control using epics software, web compatible
• Omega motorized rotation with water cooling for
  high temperature studies of single crystals

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User Program

• Open for proposals from anyone
• Receiving 4 proposals per beam-time cycle
• 4 different groups have used the system