Laser heating in the diamond anvil cell: The «basics» Denis ANDRAULT Laboratoire Magmas et Volcans Université Blaise Pascal First scientific articles based on LH-DAC (WoS): In canberra, Australia: Lin- Gun JIU (1974) discovery of the (Mg,Fe)SiO3 brigmanite, the major mineral on Earth. He then wrote ~10 other major articles based on LH-DAC. In Washington-DC: By: T. YAGI, H.K. MAO, P.M. BELL (1978) Bridgmanite Photo: Pierru et al. In Hawaï (?), USA: L.C. MING and M.H. MANGHNANA (1979) Phase transition in MgF2 In Paris: A. LACAM, M. MADON, J.P. POIRIER (1980) Upper-Lower mantle discontinuity on Earth First article using X-ray diffraction coupled with LH-DAC (WoS): In canberra, Australia: Lin-Gun JIU (1974) discovery of the (Mg,Fe)SiO3 brigmanite. First articles using synchrotron radiation coupled with LH-DAC (WoS): In Washington-DC: Y. KUDOH, C.T. PREWITT, L.W. FINGER (1990). Bridgmanite EoS In Mainz, Germany: R. BOEHLER, N. VONBARGEN, A. CHOPELAS (1990). Melting of Fe First article using ESRF and LH-DAC (WoS): S.K. Saxena, L.S. Dubrovinsky, P. Lazor et al. (1996) Breakdown of perovskite (MgSiO3) in the Earth's mantle G. Fiquet, D. Andrault, A. Dewaele et al. (1998) P-V-T equation of state of MgSiO3 perovskite
At the first glance, one could think that LH-DAC techniques did not evolved much in recent years Membrane Infrared laser He-loader C A D A = Piston B= Cylinder C= Cap B D= WC seats Re Gasket Chervin-type DAC Diamond Infrared laser Ca librant => Pressure Radiation => Temperature In fact, there is a continual, and critical, evolution in the control of experimental conditions for a large part thanks to the use of synchrotron radiation
What is the limitation in pressure generation when using laser heating ? 1 bar Culet of e.g. 250 μ m High P Ideal laser heating Bevel up to ~60 GPa 10/300 μ m Hemley et al., 1997 1 bar Bevel of e.g. 100/300 μ m High P Laser heating is still fine! Max 200-300 GPa No laser heating is possible witho ut some The maximum pressure is ~300 GPa today space (microns) between the hot sample for temperatures of several 1000 K and the cold diamonds
What is the temperature limitation in the LH-DAC ? Temperature measurement I do not known a limitation today at ID27 Intensity (a.u.) Raw pattern Intensity / system-response (a.u.)(nm) T = 6250 K 400 600 800 1000 Wavelength(nm) T = 5200 K Int. / Sys-Resp 6140 K Corrected for T = 3800 K system response 1.8 1.6 1.4 1.2 T = 2900 K 1/wavelength (10 6 m -1 ) T = 1250 K 7000 Two-color 6000 temperature 5000 600 650 700 750 800 850 900 4000 Wavelength (nm) 650 700 750 800 850 Wavelength(nm) For measurement at high T, use reflective objectives !
Use of reflective objectives... Spectrometer entrance pinhole Intensity / system-response (a.u.)(nm) T = 6250 K Hot T = 5200 K sample T = 3800 K T = 2900 K T = 1250 K As we need the light intensity as a fonction of � any chromatic abheration disables 600 650 700 750 800 850 900 the temperature measurement Wavelength (nm)
How to be sure that the sample properties are measured in the laser hot spot ? Visualisation and alignement of the X-ray beam The use of pico or piezo motors is very convenient for the Warning: The good optical alignement must be checked carrefully Spectrometer at high laser power ! entrance Alignement of the laser spot Misaligned : 1500 K Aligned : 1500 K 2500 K
Can we resolve the radial temperature gradient using a very small sample ? Large sample Small sample No energy deposited Energy Energy 1 μm away from the sample deposited deposited Temperature Temperature High k Pressure medium thermal Temperature low k conductivity No, in most cases, it makes the radial gradient even worse !
How critical Radial is the radial temperature temperature gradient gradient ? Pressure medium thermal conductivity Two end-members situations arise FWHM 20-30 μm High k Low k Cold diamonds axial temperature gradients FWHM << sample ~ Constant thickness temperature Diamond: ~500K Glass < 1000K Take away message: Melt > 4000K Minimizing the axial temperature gradient is often the major Melting of the Earth’s mantle Fiquet et al., 2010
Do I need double sided laser heating for my sample ? (I promised Laser absorption at the sample surface: Need 2 sides heating - Oxide heated by CO2-laser Laser absorption in the bulk of the sample (at � =1μm): - Oxide mixed with Pt-absorber power - (Mg,Fe)-minerals Thermal conductivity of pressure medium => Sample Sample =>
What is the sample pressure in the laser spot ? We were successful to Energy FInite element model synthesize a HP polymorph Dewaele et al., 1998 deposited based on thermal pressure on sample 30 Mg 2 SiO 4 Temperature 28 PV + PER 26 Theoretical 24 thermal Pressure (GPa) 22 pressure Ringwoodite � Pth= � K � T 20 Wadsleyite 18 Exp Relaxation of 16 the pressure 14 gradient Olivine L 12 True pressure increase from 1473 1873 2273 2673 3073 0.2 to 0.8 � Pth Temperature (K ) => It is not possible to measure a PVT EoS without an internal pressure calibrant (e.g. Pt for MgSiO3)
Any potential problem with chemical migration in the laser spot ? Yes, major problems ! Chemical analyses of olivine (Mg,Fe)2SiO4 recovered after laser scan of the laser over the entire sample surface For this reason, the LH-DAC cannot provide constrains on the Equation of state of Fe (Mg,Fe)-minerals; the interdiffusion is too easy. We need fast measurements Si => ESRF-EBS
Any potential problem of chemical pollution of the sample ? Reported solidus for various mantle compositions Fiquet et al. Infrared absorption of the recovered sample Andrault et al. => 1510 ppm water Boehler et al. Nomura et al. => For high-T studies, always load (Nomura et al., 2014) is a wet-solidus...
Any potential problem with chemical polution of the sample Yes, major problems ! Anzellini et al., 2013 At very high temperature, the diamond anvils to metallic sample. The Fe-C melting curve is much lower than that of pure Fe Boehler et al. (several) Only fast measurements can solve the melting curve of pure Fe We need fast measurements => ESRF-EBS
How critical is the size of the X-ray probe ? Probe size >> hot spot Then, the data set can be deconvoluted: Mossbauer spectrum registered at ID18 Deconvolution of a mixture of The laser can be scanned Fe2+ (LS & HS) in ferropericlase several minutes on the sample Fe2+ (LS and IS) and Fe3+ (LS) in bridgmanite for partial homogeneization Probe size WE NEED Probe size << hot spot => Good configuration: Small radial temperature gradient on sample ESRF-EBS
How critical is the size of the X-ray probe ? Melting of pyrolite at P=78 GPa Probe size << hot spot + short acquisition time => This allows the mapping of the sample properties 1.0 a Mg-Pv 0.9 0.8 0.7 X-ray 0.6 Liq 0.5 difgraction Melting of a basalt at P=120 GPa 0.4 0.3 Pv 0.2 0.1 0.0 b Fe 36000 32000 Ext 28000 X-ray 24000 Liq 20000 fuorescence 16000 12000 Pv 8000 10 μ m 4000 0 c 1.0 Fe-XRF Intensity 0.9 Liq 0.8 Fe-content 0.7 0.6 Ext Pv Electron microprobe Mineralogical mapping 0.5 0 10 20 30 40 in situ X-ray difgraction Chemical mapping Position (a.u.)
Is any type of measurement available in the LH-DAC at ESRF ? To date, these types of measurements were performed: - X-ray absorption (XANES) - Inelastic scattering (phonons) - Mössbauer spectroscopy - X-ray emission spectroscopy - X-ray raman (?) - and maybe others ? For some techniques, some limitations remain in : - Acquisition time - Size of the beam - Absorption of diamond window will make the LH-DAC system even more suited
CO 2 or YAG laser Argon medium Ruby Re gasket Sample Diamond Thanks for your attention! Any comments on my «questions» ? Any additional question that «we» would comment ?
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