laser heating in the diamond anvil cell by shuifanglj

VIEWS: 25 PAGES: 16

									laser heating in the
diamond anvil cell
       the goals
• mineral properties at high
 P,T
• constrain phases,
 temperature, and
 composition of earth &
 planets’ interiors
• understand transport
 behavior --heat and mass--
 throughout the earth’s
 interior
the measurements
• melting temperature(s)
• phase stability
• compressibility/thermal
 expansion
• chemical partitioning
• thermal
 diffusivity/viscosity/electrical
 conductivity
        experimental steps

1. heat sample
2. measure
  temperature
3. measure
  phenomena
                 photos courtesy of A. Jephcoat
1. measuring temperature


a.absolute temperature measurement
b.relative temperature measurement
                                    120

                                    100                                                      2500 K
                                                                                            
                                                                                                                      biggest accuracy error --
                       )
               -1
                       Å




                                         80
                                                                                                                      graybody approximation
               -2




                                                                                2500 K
                       Intensity (W m




                                         60                                      decrea ses from 1 to 0.7
                                                                                across wavelength range
                                                                                (T gray body = 2667 (2))
                                         40
                                                                                                                      emissivity sample dependent
                                         20
                                                 Dark coun t
                                                 (from Kavner,Duffy, Sh en FeS data)
                                          0
                                         5000              6000     7000             8000       9000          10000
                                                                    Wavelength (Å)
                                                                                                                      don’t use “wien’s plot”
                                         -6



                                         -8
                                                                            2498.8(1 )
                                                                                                                      second biggest error--
                                                                                                                      chromatic aberration,
Normalized Intensity




                                        -10

                                                                  2667(2)
                                                                                                                      especially around steep
                                        -12
                                                                             1768(13)
                                                                                                                      intensity gradients
                                        -14



                                        -16            3
                                              -28x10        -26    -24         -22       -20      -18         -16
                                                                  Normalized frequency
                       relative temperature
                             (gradients)
                       100


                                                0 GPa
                                              FWHM > 100 µm

                        80
Temperature (% peak)




                        60                     12 GPa
                                             FWHM = 48 µm


                                                20 GPa
                                              FWHM = 37 µm

                        40

                                           X-ray beam width

                             -20     -10          0           10   20
                                           Distance (µm)




                                   this is 1-di radial.
        laser heating system design

            Laser
Video




                   B
                               A
               intensity
                           temperature
               gradient
                           measurement
             measurement
              120
                                                                                                                                                            Intensity at  = 500nm
                                                                2500 K
                                                                                                                                          40           1
              100                                                                                                                                           10000
                                                               
 )




                                                                                                                    distance (~microns)
-1




                                                                                                                                                            1e+08
                                                                                                                                          20
 Å




                  80



                                                                                                       +
                                                                                                                                                            1e+10
-2




                                                   2500 K
 Intensity (W m




                  60                                decrea ses from 1 to 0.7                                                             0
                                                   across wavelength range
                                                   (T gray body = 2667 (2))
                  40
                                                                                                                                          -20
                                                                                                                                                               1e+06
                  20
                         Dark coun t                                                                                                      -40                   100
                                                                                                                                                                       1
                         (from Kavner,Duffy, Sh en FeS data)
                   0
                  5000       6000         7000        8000         9000                        10000                                            -40   -20      0           20   40
                                          Wavelength (Å)                                                                                               distance (~µm)

temperature in one place                                                                                            intensity everywhere  600
                                                                                          40
                                                                                                               1000
                                                                    distance (~microns)




                                                                                                               1400
                                                                                          20
                                                                                                                                                        temperature

                                   =                                                                                                                     everywhere
                                                                                           0
                                                                                                             2400
                                                                                                             2000
                                                                                      -20                    1600
                                                                                                             1200
                                                                                                                                                       (2-dimensions)
                                                                                      -40                    800



                                                                                               -40     -20     0                          20    40
                                                                                                       distance (~µm)
            I-measure spectrometer requirements
                                                                       uniformity in pixel
            30
            2
            27
            2
                           500 nm
                                                650 nm
                                                                       response
            24
            2
            21
            2
            18
                                                                       linear response over
Intensity




            2
            15
            2
                                                  800 nm
                                                                       a high dynamic
            12
            2
            2
                9
                                                                       range
                6
            2
                3
            2
                0
                                                   full range          good spatial optics
            2
                    1000       1500      2000       2500        3000
                                    Temperature (K)
                                                                       can employ different
                                                                       filters as an internal
                                                                       consistency check
  2. determining pressure
• mix two materials together in the
 diamond cell, and assume they feel the
 same pressure
• with a “known” P(V,T) equation of state,
 use lattice parameters determined from
 standard to calculate the pressure
• current important topic:  differing eqns.
 of state for gold yield ~2GPa difference
 at P,T of Earth’s transition zone
• but how good is our assumption of
 pressure continuity?
                                 predictions                            traceable to
                                                                          different
                                                                        equations of
              stress continuity strain continuity   strength effects        state

   Pt and     PPt = Prw PPt > Prw PPt < Prw PPt ≥ Prw
ringwoodite

  ruby and
  hydrous      Prf = Prw         Prf > Prw          Prf > Prw          Prf ≥ Prw
ringwoodite


Pt and MgOP
              Pt
                                           P
                 = PMgO Pt > PMgOPPt < PMgO Pt > PMgO
                       P


Pt and NaCl P
               Pt = PNaCl Pt >PNaClPPt > PNaClPPt ?PNaCl
                        P

Kung, 2003
 NaCl and     PMgO = PNaCl       PMgO > PNaCl       PMgO > PNaCl       PMgO ? PNaCl
  MgO
                                  results                               traceable to
                                                                          different
                                                                        equations of
              stress continuity strain continuity   strength effects        state

   Pt and     PPt = Prw PPt > Prw PPt < Prw PPt ≥ Prw
ringwoodite


  ruby and     Prf = Prw         Prf > Prw          Prf > Prw          Prf ≥ Prw
ringwoodite



Pt and MgOP
              Pt
                                           P
                 = PMgO Pt > PMgOPPt < PMgO Pt > PMgO
                       P

          P
Pt and NaCl
              Pt = PNaClP >P   PPt > PNaClPPt ?PNaCl
                         Pt NaCl
Kung, 2003
 NaCl and     PMgO = PNaCl       PMgO > PNaCl       PMgO > PNaCl       PMgO ? PNaCl
  MgO
   What’s hot            What’s not

     separate
                           imaging
 temperature and
                      spectroradiometry,
   temp-gradient
                     chromatic aberration
  measurements
controlled-geometry assuming hydrostaticity
    composites       Reuss/Voigt bounds

								
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