laser heating in the diamond anvil cell

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 goals

the measurements melting temperature(s) phase stability compressibility/thermal expansion chemical partitioning thermal diffusivity/viscosity/electrical conductivity

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

a. absolute temperature measurement b. relative temperature measurement 1. measuring temperature

biggest accuracy error -- graybody approximation emissivity sample dependent don’t use “wien’s plot” second biggest error-- chromatic aberration, especially around steep intensity gradients

relative temperature (gradients) this is 1-di radial.

laser heating system design A temperature measurement B intensity gradient measurement Video Laser

= + temperature in one place intensity everywhere temperature everywhere (2-dimensions)

temp-measure spectrometer requirements temperature: hotspot average or in one place or aperture scanned across hotspot

I-measure spectrometer requirements uniformity in pixel response linear response over a high dynamic range good spatial optics can employ different filters as an internal consistency check

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? 2. determining pressure

K A, µ A t A K B, µ B, t B K A, µ A t A K B, µ B, t B behavior of composites in the diamond cell hydrostatic not hydrostatic constant stress constant strain 2-phase system P A = P B P A ≠ P B e A = e B if K A > K B then P A > P B if t A > t B then P A > P B A is matrix and B 2nd phase if t A < t B then P A = P B

predictions stress continuitystrain continuitystrength effects Pt and ringwoodite ruby and hydrous ringwoodite Pt and MgO Kung, 2003 NaCl and MgO traceable to different equations of state P Pt = P rw P Pt > P rw P Pt < P rw P Pt ≥ P rw P rf = P rw P rf > P rw P rf ≥ P rw P Pt = P MgO P Pt > P MgO P Pt < P MgO P Pt > P MgO P MgO = P NaCl Pt and NaCl P Pt = P NaCl P Pt ?P NaCl P Pt > P NaCl P MgO > P NaCl P MgO ? P NaCl

results stress continuitystrain continuitystrength effects Pt and ringwoodite ruby and ringwoodite Pt and MgO traceable to different equations of state P Pt = P rw P Pt > P rw P Pt < P rw P Pt ≥ P rw P rf = P rw P rf > P rw P rf ≥ P rw P Pt = P MgO P Pt > P MgO P Pt < P MgO P Pt > P MgO Pt and NaCl P Pt = P NaCl P Pt ?P NaCl P Pt > P NaCl Kung, 2003 NaCl and MgO P MgO = P NaCl P MgO > P NaCl P MgO ? P NaCl

What’s hot What’s not separate temperature and temp-gradient measurements imaging spectroradiometry, chromatic aberration controlled-geometry composites Reuss/Voigt bounds assuming hydrostaticity