Simultaneous determination of elastic and structural properties under simulated mantle conditions using multi-anvil device MAX80

Abstract

An ultrasonic interferometry high-pressure set-up for elastic wave velocity measurements under simulated Earth's mantle conditions has been developed. A DIA-type multi-anvil apparatus MAX80 permanently located at HASYLAB, Hamburg, Germany for X-ray diffraction (XRD) under in situ condition was equipped for simultaneous ultrasonic measurements. Two of the six anvils were equipped with lithium niobate P-and S-wave transducers of 33.3 MHz natural frequency. The pressure and temperature limits of the high-pressure apparatus were not reduced as a side effect of the modification. The ultrasonic configuration allows all kinds of interferometric measurements with compressional and shear waves. In addition to the classical ultrasonic interferometry the newly developed data transfer function technique (DTF), first described in [J. Phys. Condens. Matter 14 (2002) 11337], is discussed in detail to give the readers the chance to use this valuable and important new method.The results for natural San Carlos olivine up to 3 GPa pressure are compared with published data of several authors. The data for hot-isostatic-pressed anorthite solved discrepancies between published high-pressure and normal-pressure data for polycrystalline anorthite leading to v p ¼ 7.28 km/s, v s ¼ 3.93 km/s at ambient conditions and dv p =dp ¼ 0.027 km/s GPa, dv s =dp ¼ 0.001 km/s GPa. The obtained data sets correspond to published results within the accuracy of the method.As an example for unquenchable phase transitions we measured the elastic wave velocities at the high-pressure clinoenstatite (MgSiO 3 , HCEn) -low-pressure (LCEn) transition at high pressure, high temperature conditions in conjunction with in situ XRD. For ultrasonic interferometry experiments LCEn powder synthesized at ambient pressure was hot-isostatic-pressed at 0.4 GPa and 14008C for 2 h in MAX80 to obtain low-porosity samples. The elastic wave velocities v p and v s of the CEn sample were measured in situ using the classical interferometric technique as well as the recently developed ultrasonic data transfer function (DTF) technique for the elastic wave velocities as a function of pressure at 7008C. To compare the results, v p and v s were measured at 6.7 and 7.5 GPa using both interferometric techniques. The results correspond within the limits of less than 1%.

Calibration based on a primary pressure scale in a multi-anvil device

“…Knoche et al (1997Knoche et al ( , 1998) had a hot isostatically pressed forsterite sample between two platinum buffer rods. Consequently, the condition mentioned can be a good approximation for high-strength samples, as it was also the case in our experiments with San Carlos olivine, anorthite, clinoenstatite, and Calibration based on a primary pressure scale in a multi-anvil device 433 quartz (see Mueller et al (2004), page xxx, this volume), but not if a ductile sample is taken into account.…”

“…The sample is surrounded by rings made from boron nitride or glass ceramics for electrical insulation and as a quasi-hydrostatic pressure transmitting medium. Further details of the apparatus are described by Mueller et al (2004) on page xxx, this volume and also by Mueller et al (2002). …”

“…At the latest when we introduced an ultrasonic data transfer function technique at MAX80 (see Mueller et al (2004), page xxx, this volume) the XRD-scanning method was Q1 no longer adequate as the only available length measurement technique. A digital ultrasonic sweep for v p and v s lasts about 90 min.…”

Multianvil techniques in conjunction with synchrotron radiation at Deutsches ElektronenSYnchrotron (DESY) – HAmburger SYnchrotron LABor (HASYLAB)

“…The experiments demonstrated that maximum pressures at least 25% higher compared to the standard MAX80 confi guration are easily achievable while using prefabricated gaskets. Further benefi ts are a reduced number of blowouts, i.e., decompression of the cell assembly by gasket failure, and higher X-ray intensity at peak pressures due to the larger gap width between the anvils (Mueller et al, 2005a).…”

“…Otherwise the intense X-rays would destroy the CCD (Charge-Coupled Device) chip of the camera and would cause radiation damage in the optical glass of the lenses. The limit of the optical resolution is determined by the wavelength of green light of ~0.5 μm and the aperture of the objective of less than 0.5 to a total of ~1 μm (Mueller et al, 2005a). The minimum object distance is a strongly limiting factor for the selection of useful objectives.…”