MR53A-01
Multi-anvil High Pressure Facility at National Synchrotron Light Source: Then, Now, and Future
Multi-anvil high pressure facility (Beamline X17B2) at National Synchrotron Light Source (NSLS) was the first of its kind established in the United States with the support from NSF through the Center for High Pressure Research (CHiPR, 1990 - 2002). During this period, the facility provided a fertile ground for steep growth of research on earth materials at simultaneously high pressures and temperatures. Main areas of study included the thermoelastic and structural properties of minerals, phase equilibria, rheology, acoustic velocities, kinetics of phase transformations, and physical properties of melts. The rheological and acoustic measurements at high pressures in conjunction with synchrotron were first developed at this facility, and both techniques are being adapted today by other laboratories around the world. Last five years has witnessed great increases in efficiency and productivity of this facility, a beneficiary of the construction of a permanent hutch and time-sharing mechanism made possible by NSLS, and the establishment of the Consortium for Materials Properties Research in Earth Sciences (COMPRES). While other above- mentioned areas of research continued to grow, the rheological studies of minerals experienced fast expansion through the use of two new high pressure deformation apparatus, the Deformation DIA (D-DIA) and the Rotational Drickamer apparatus (RDA, led by S. Karato from Yale Univ.) Experiments are currently being performed on various mantle minerals to derive their rheological properties. Performance of the facility will receive another boost through the addition of a monochromatic side station jointly supported by DoD, COMPRES and NSLS, and construction of the station is well underway. With continued operation of COMPRES in next five years, we will see several significant additions to the large- volume facility at NSLS: a new system for precise measurements of stress at high pressure; a 2000-ton press; D- TCup apparatus for deformation experiments at pressures up to 20 GPa; a portable RDA that can be placed in the current press; and the fully operational monochromatic side station. The planned new synchrotron (NSLS II) with its supreme energy and spatial resolutions allows further enhancement of capabilities of multi-anvil high pressure facility, and opens door for new possibilities beyond 2012.
MR53A-02
Compressibility and phase transition studies for amorphous materials under high pressure: Approach combined of synchrotron high energy x-ray diffraction and micro tomography techniques using diamond anvil cell
The structural evolution of amorphous materials under high pressure conditions is a virgin field that has not been extensively explored. Investigations by reaching large Q range using synchrotron high energy x-ray diffraction and diamond anvil cell (DAC) techniques were performed. The study of polyamorphism will undoubtedly broaden our horizons and perspectives of the states of matter in general, and may have a significant impact on the existing theories about the structure, formation, and evolution of amorphous materials. The procedure of the pressure- induced amorphous state to crystalline state is another interesting subject. Combine the high energy x-ray diffraction with the time resolved area detector, we not only could accurately measure the structural factors evolution of amorphous materials under pressure, but also could record the time dependence of the crystallization procedure. These will provide new insight on the nature of crystallization, provide new invitation for the electronic theoretical studies for the phase stability and competition in time and spatial domains, and improve our understanding of the kinetic process of the common pressure induced crystallization. Another technical development effort is the micro tomography study using DAC at radial geometrical setting. Although the two-dimensional imaging, i. e. x-ray radiography, is used in routine way for high pressure DAC experiments, the ”®volume imaging', i. e. x-ray tomography, will offer us more information regarding direct volume measurement, relative density measurement, and shear deformation under high pressure. The application in high pressure conditions by using DAC will greatly push our understanding of deformation mechanism down to lower mantle conditions. Another major application for DAC tomography will be the relative density measurement for the amorphous materials, metallic glasses, and liquid or melt in DAC under pressure, which will provide better information for the density of non-crystalline materials under pressure than the routine x- ray radiography. We will demonstrate the preliminary studies on DAC tomography for amorphous selenium, zinc oxide, gold and nickel polycrystal samples under pressure.
MR53A-03
Characterization of Al-Si Ordering State in Alkali Feldspar Using ALCHEMI
Atom Location by CHanneling-Enhanced MIcroanalysis (ALCHEMI) is used in this study to determine the occupancy of Al atoms in the T1o site (t1o) of alkali feldspar. Combined with the method shown by Taft?and Buseck (1983), analytical electron microscopy proves to be a viable technique for fully characterizing the Al-Si ordering state in the feldspar framework. We have applied this method to both gem orthoclase from Itrongay, Madagascar, and to its heated counterpart. Our preliminary results give 0.737 and 0.372 as 2t1 (= t1o + t1m) and t1o respectively for the original orthoclase, versus 0.517 and 0.256 for heated orthoclase. Standard X-ray powder diffraction experiments will be done to verify these measurements. Furthermore, we are seeking a quantitative relationship between the incident electron intensity based on the Bloch-wave formulation and the positions of interstitial sites with respect to the reference channeling plane. This approach could give a more precise interpretation of ALCHEMI data in our case and in similar applications.
MR53A-04
Synchrotron Infrared Reflectivity of Iron at High Pressure
High temperature diamond anvil cell experiments often rely on spectroradiometry for temperature measurement. One of the biggest uncertainties in fitting the emission spectra of the sample is the unknown spectral emissivity of the sample material. We have measured the infrared reflectivity of iron at pressures up to 50 GPa and room temperature at the U2A beamline of the National Synchrotron Light Source using the Fourier Transform Infrared Reflectivity technique in order to evaluate the greybody assumption often applied in spectroradiometry. The emissivity and other optical properties were derived with a Kramers-Kronig analysis. The reflectivity undergoes a discontinuous change in both slope and magnitude at the body centered cubic (bcc) to hexagonal close packed (hcp) phase transition in iron. The data shows that at room temperature, hcp iron is nearly a perfect greybody whereas the emissivity of bcc iron deviates from a greybody.
MR53A-05
Fine Measurements of Geomaterials Thermoelastic Properties at Megabar Pressures
Accurately measuring the thermoelastic properties of geomaterials in the megabar pressure range is of first importance to correctly modelize the deep Earth. Thanks to recent developments and experimental improvements done on synchrotron radiation facilities, new standards in terms of level of detail and measurements accuracy have been achieved. In a recent work done on the post-perovskite phase MgSiO3 (N. Guignot et al., EPSL 256 (2007), 162-168), we could show that the thermal properties of that phase could be measured with a very high resolution, up to 140 GPa and 2500 K. Moreover, we could measure the post-perovskite phase elastic anisotropy with great details. The agreement between experiment and theory is observed to be very good. This study was a good opportunity to show the importance of not only accurate pressure scales and temperature measurements, but also correct equation of state mathematical formulations. We have recently performed a new experiment on iron up to 165 GPa and 3000 K at ESRF ID27 high pressure beamline. In order to accurately measure the P-V-T equation of state of epsilon-iron, MgO is added to the sample. NaCl is used as a thermal insulator. We see in that case that great care must be taken on a possible water contamination: a certain amount of iron can be oxidized and integrated in periclase, leading to wrong pressure measurements. Again, the data (approximately 200 P-V-T points) can be used to get the epsilon-iron P-V-T equation of state with a good resolution.
MR53A-06
Ultrasonic elastic wave velocity measurements of MgO at high pressures and high temperatures with standard-free pressure calibration
Pressure determination in high-pressure X-ray diffraction experiment is one of the most crucial uncertainties for determining the location of phase transition in the Earthfs deep interiors. MgO is frequently used as a pressure standard using the previously published equation-of-state, while pressure calibration for determining the equation-of-state remains unsolved because of the lack of direct measurement of sample pressure. Here we carried out high pressure X-ray diffraction experiments combined with ultrasonic elastic wave velocity measurement up to 1650 K and 17.7 GPa of NaCl scale (Decker, 1971), and determined sample pressure without pressure standard. High-pressure experiment was carried out using the Kawai-type apparatus (SPEED-1500) in BL04B1 beamline at SPring-8. The unit cell volume of MgO, Au, and NaCl and resultant their densities were determined from X-ray diffraction measurements. Elastic wave velocities of MgO were determined from elastic wave travel time and sample length which was measured using X-ray radiography. Adiabatic bulk modulus of MgO at each pressures and temperatures were determined using the observed compressional and shear wave velocities, and density. Then we determined zero pressure isothermal bulk modulus and its pressure and temperature derivatives with fixed zero pressure thermal expansion coefficient, Gruneisen parameter and its volume dependence, and calculated pressure using the Birch-Murnaghan equation of state. Our derived pressures at 300 K are consistent with those calculated with the Au (Anderson et al., 1989) and NaCl (Decker, 1971) scale up to ~10 GPa, while is higher than those of Au and NaCl scale above ~10 GPa. The difference of pressure from the Au and NaCl scale continuously increases with increasing pressure, and reaches to ~1GPa at ~16-18 GPa. At high temperatures we also observed difference in pressure between our equation- of-state and the scale of Anderson et al. (1989) and Decker (1971) above ~10 GPa. The misunderstanding in pressure derived from the Au and NaCl scale would give significant influence on understanding the depth of phase transition in the Earthfs deep interiors.
MR53A-07
Toward a self-consistent pressure scale: elastic moduli and equation of state of MgO by simultaneous x-ray density and Brillouin sound velocity measurements at high-pressure high-temperature conditions
Accurate phase diagrams and PVT equations of state (EOS) of materials strongly depend on the PVT calibrations of standard materials (e.g. MgO, NaCl, Au, Pt), which currently do not predict identical pressures at the same experimental conditions. MgO is commonly used as a pressure standard in a variety of high pressure and high- temperature experiments. Despite being one of the simplest and most studied materials, its accurate EOS is still uncertain, especially at high PT. The direct way of obtaining a self consistent pressure scale is by measuring acoustic velocities (Vp and Vs) and density simultaneously. Such P-V-T-Vp-Vs measurements allow one to determine the pressure directly, without resort to a separate calibration standard. Recently, as part of a major COMPRES initiative, we have constructed a Brillouin spectrometer at GSECARS, APS (13-BM-D) which allows accurate simultaneous sound velocity and lattice parameter measurements at high pressures and high temperatures. Such measurements were performed on single crystal MgO at simultaneously high pressures (up to 30 GPa) and high temperatures (up to 873K) in diamond cells with Ne or Ar as pressure medium. At each PT point we measured the unit cell parameters and the acoustic velocities of MgO in several crystallographic directions, and directly obtained all three single crystal elastic moduli, as well as isotropic adiabatic bulk (KS) and shear (μ) moduli. Unit cell parameters of pressure medium (Ne, Ar) and additional pressure calibrants (Au, Pt, NaCl) were measured at each PT for cross calibration. The results of these experiments and implications for a self consistent P-V-T(-Vp-Vs) pressure scale will be presented and discussed.
MR53A-08
DTF-Ultrasonic Interferometry and Standard-Free Pressure Measurement in Multi-Stage Multi- Anvil Devices
A promising way to increase the maximum pressure of multi-anvil devices is "multi-staging", i.e. implementing an additional set of "sub-anvils" between anvils and sample resulting in a better distribution and limitation of the stress inside the anvils. Contrary to the common opinion of overshooting the maximum crushing strength most of the anvils fail in high pressure experiments due to the exceeding of the maximum tensile stress as a result of the lateral deformation. Utsumi et al., 1986 published a technique to reach 60 GPa pressure by using sintered diamond anvils as second stage in a single-stage DIA-type multi-anvil apparatus. Li, 2001 published a peak pressure of more than 26 GPa for a single-stage DIA even though the diamond anvils had been broken. Wang & Utsumi, 2005 (pers. comm.) reported similar experiments performed in a deformation-DIA (D-DIA). Our experiments with two LVP's installed at DESY-HASYLAB also showed more than a pressure doubling in comparison to the original single-stage and double-stage configurations, i.e. 25 GPa at MAX80 and nearly 50 GPa at MAX200x (Mueller et al., 2006, 2007). The first ultrasonic experiments in this configuration were performed at MAX80. The top sub-anvil was acoustically coupled to the upper anvil equipped with a triple-mode ultrasonic transducer by a platinum disk of the same diameter as the cylindrical shaft of the sub-anvil. From acoustical point of view the travel path has 3 buffer rods - top MAX80 anvil, platinum disk, upper internal opposed anvil - and the bottom internal opposed anvil as reflector. As a result of preparatory experiments we had found the upper cut-off frequency for the existing transducer-TC-anvil system at about 320 MHz. An excitation function representing the bandwidth of 100 to 300 MHz was calculated and used in the data transfer function (DTF) ultrasonic interferometry experiment. NaCl was simultaneously used as pressure calibrant, using the EoS of Decker (1971), and sample for ultrasonic interferometry (Mueller et al., 2003, 2005). The compressibility results, derived from the ultrasonic data, were compared with data of static compression experiments up to 5 GPa (Bridgman, 1940) and up to 30 GPa (Birch, 1986) using experimental data from Boehler & Kennedy (1980) and Fritz et al. (1971). http://www.gfz-potsdam.de