Phase comparison and equation of state for TaO.

Tantalum pentoxide (TaO) is among the most technologically useful heavy transition metal oxides. Unfortunately, its crystal structure is the subject of long-standing and unresolved disagreement. Among other consequences, this uncertainty has made it impossible to formulate a robust high pressure equation of state for TaO.

A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell.

An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolved MHz X-ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤10 s), where up to 352 diffraction images can be collected from a single pulse train.

Cinema:Snap: Real-time tools for analysis of dynamic diamond anvil cell experiment data.

We developed tools and a workflow for real-time analysis of data from dynamic diamond anvil cell experiments performed at user light sources. These tools allow users to determine the phases of matter observed during the compression of materials in order to make decisions during an experiment to improve the quality of experimental results and maximize the use of scarce experimental facility time. The tools fill a gap in dynamic compression data analysis tools that are real-time, are flexible to the needs of high-pressure scientists, connect to automated processing of results, can be easily incorporated into workflows with existing tools and data formats, and support remote experimental data analysis workflows.

X-ray Free Electron Laser-Induced Synthesis of ε-Iron Nitride at High Pressures.

The ultrafast synthesis of ε-FeN in a diamond-anvil cell (DAC) from Fe and N under pressure was observed using serial exposures of an X-ray free electron laser (XFEL). When the sample at 5 GPa was irradiated by a pulse train separated by 443 ns, the estimated sample temperature at the delay time was above 1400 K, confirmed by transformation of α- to γ-iron. Ultimately, the Fe and N reacted uniformly throughout the beam path to form FeN, as deduced from its established equation of state (EOS).

A broadband wavelet implementation for rapid ultrasound pulse-echo time-of-flight measurements.

A broadband wavelet approach to ultrasonic pulse-echo time-of-flight measurements is described. The broadband approach significantly reduces the time required for frequency-dependent pulse-echo measurements, enabling studies of dynamic systems ranging from biological systems to solid-state phase transitions. The described broadband approach is demonstrated in parallel with the more traditional frequency stepping approach to perform ultrasound time-of-flight measurements inside a large volume Paris-Edinburgh press in situ at a synchrotron source.

Experimental melting curve of zirconium metal to 37 GPa.

In this report, we present results of high-pressure experiments probing the melt line of zirconium (Zr) up to 37 GPa. This investigation has determined that temperature versus laser power curves provide an accurate method to determine melt temperatures. When this information is combined with the onset of diffuse scattering, which is associated with the melt process, we demonstrate the ability to accurately determine the melt boundary.

Room-temperature compression and equation of state of body-centered cubic zirconium.

Zirconium (Zr) has properties conducive to nuclear applications and exhibits complex behavior at high pressure with respect to the effects of impurities, deviatoric stress, kinetics, and grain growth which makes it scientifically interesting. Here, we present experimental results on the 300 K equation of state of ultra-high purity Zr obtained using the diamond-anvil cell coupled with synchrotron-based x-ray diffraction and electrical resistance measurements. Based on quasi-hydrostatic room-temperature compression in helium to pressure P  =  69.

High frequency signal acquisition using a smartphone in an undergraduate teaching laboratory: Applications in ultrasonic resonance spectra.

A simple and inexpensive approach to acquiring signals in the megahertz frequency range using a smartphone is described. The approach is general, applicable to electromagnetic as well as acoustic measurements, and makes available to undergraduate teaching laboratories experiments that are traditionally inaccessible due to the expensive equipment that are required. This paper focuses on megahertz range ultrasonic resonance spectra in liquids and solids, although there is virtually no upper limit on frequencies measurable using this technique.

The acoustic nonlinearity parameter in Fluorinert up to 381 K and 13.8 MPa.

This work reports on the determination of the acoustic nonlinearity parameter, B/A, from measured sound speed data, in Fluorinert FC-43 at temperatures up to 381 K and pressures up to 13.8 MPa using the thermodynamic method. Sound speed was measured using Swept Frequency Acoustic Interferometry at 11 pressures between ambient and 13.

An acoustic resonance measurement cell for liquid property determinations up to 250 °C.

This paper reports on the development of a compact, rugged, and portable measurement cell design for the determination of liquid sound speed at temperatures up to 250 °C and pressures up to 3000 psi. Although a significant amount of work exists in the literature on the characterization of fluids, primarily pure water, over a wide range of pressures and temperatures, the availability of experimentally determined sound speed in water between 100 °C and 250 °C is very limited. The need to measure sound speed in liquids up to 250 °C is of both fundamental interest, as in the case of basic equations of state, and applied interest, such as for characterizing geothermal or petroleum downhole environments.

Assessment of langatate material constants and temperature coefficients using SAW delay line measurements.

This paper reports on the assessment of langatate (LGT) acoustic material constants and temperature coefficients by surface acoustic wave (SAW) delay line measurements up to 130 degrees C. Based upon a full set of material constants recently reported by the authors, 7 orientations in the LGT plane with Euler angles (90 degrees, 23 degrees, Psi) were identified for testing. Each of the 7 selected orientations exhibited calculated coupling coefficients (K(2)) between 0.

Pulse echo and combined resonance techniques: a full set of LGT acoustic wave constants and temperature coefficients.

This work reports on the determination of langatate elastic and piezoelectric constants and their associated temperature coefficients employing 2 independent methods, the pulse echo overlap (PEO) and a combined resonance technique (CRT) to measure bulk acoustic wave (BAW) phase velocities. Details on the measurement techniques are provided and discussed, including the analysis of the couplant material in the PEO technique used to couple signal to the sample, which showed to be an order of magnitude more relevant than the experimental errors involved in the data extraction. At room temperature, elastic and piezoelectric constants were extracted by the PEO and the CRT methods and showed results consistent to within a few percent for the elastic constants.