HRPD-X; a proposed upgrade to the ISIS High-Resolution Powder Diffractometer

HRPD-X is a proposal to completely replace the current high-resolution powder diffractometer (HRPD) at the ISIS Neutron and Muon Source. The new instrument is expected to deliver a factor of four increase in solid-angle coverage. Taking advantage of new detector technology and coupled with a non-magnetic sample tank and improved incident- and diffracted-beam collimation, the new instrument will substantially improve HRPD’s scientific capabilities to study magnetic structures and behaviour, high-pressure phenomena and supramolecular structures whilst strengthening its performance in already-established areas.

Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven α↔ϵ phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures.

Optimizing high-pressure pair distribution function measurements in diamond anvil cells

Pair distribution function (PDF) methods have great potential for the study of diverse high-pressure phenomena. However, the measurement of high-quality, high-resolution X-ray PDF data (toQmax > 20 Å−1) remains a technical challenge. An optimized approach to measuring high-pressure total scattering data for samples contained within a diamond anvil cell (DAC) is presented here. This method takes into account the coupled influences of instrument parameters (photon energy, detector type and positioning, beam size/shape, focusing), pressure-cell parameters (target pressure range, DAC type, diamonds, pressure-transmitting media, backing plates, pressure calibration) and data reduction on the resulting PDF. The efficacy of our approach is demonstrated by the high-quality, high-pressure PDFs obtained for representative materials spanning strongly and weakly scattering systems, and crystalline and amorphous samples. These are the highest-resolution high-pressure PDFs reported to date and include those for α-alumina (toQmax = 20 Å−1), BaTiO3(toQmax= 30 Å−1) and pressure-amorphized zeolite (toQmax = 20 Å−1).