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An experimental physicist who performed much of the work reported in the 2015 sulfur-hydride superconductivity study. A diamond anvil cell compressed the sample to very high pressure; electrical and magnetic measurements tested the transition. The reported 203-kelvin result depended on pressure and sample preparation, illustrating that a transition temperature describes a particular material state and experimental history.^[ref]

A diamond anvil cell compresses a sample between opposed diamond tips. The flat diamond anvil culets load a metal gasket whose hole holds the specimen and a pressure-transmitting medium. Transparent diamond admits excitation and returning fluorescence, enabling an internal ruby pressure sensor.^[ref]

The functions in the drawing answer different questions. The drive applies force, the gasket confines the sample, the medium transmits stress, and the ruby pressure scale assigns a local pressure from an optical signal. A large drive reading cannot establish either the sample's pressure or the absence of deviatoric stress. Optical access also permits repeated readings without unloading the sample: a change during a long measurement can be detected rather than silently folded into a material-property curve.

A gasket is a deformable component that closes a leakage path between contacting surfaces. In a diamond anvil cell, its hole also confines the sample laterally.

A high-pressure apparatus in which several anvils compress a relatively large specimen. Compared with a diamond anvil cell, it typically offers greater sample volume for synthesis and bulk measurements, with less optical access and a lower ultimate pressure range.

A multi-anvil press transmits a large external load through several hard anvils onto a confined pressure medium surrounding the sample. Reducing the loaded area raises pressure, while the surrounding medium and gasket limit lateral escape. A resistive heater within the assembly can heat the sample, with insulation and temperature sensing arranged around it. It provides relatively large sample volumes and useful bulk, high-temperature experimental conditions, but access to the sample and optical paths is restricted, pressure gradients and calibration matter, and the maximum pressure is constrained by anvil strength and geometry.

A diamond anvil cell squeezes a very small sample and pressure medium in a gasket hole between opposed diamond culets. Diamond combines high strength with useful optical transparency, permitting spectroscopy and optical pressure calibration as well as suitable X-ray access. Heating can be external or laser-based. The very small contact area permits high pressure from a modest total force, but gives a tiny sample volume. Nonhydrostatic stress, pressure gradients, gasket deformation, heating gradients, chemical compatibility and diamond failure are important limitations.

Neither device generates pressure by force alone independent of area and confinement. Nor does a nominal force-to-area ratio guarantee a known hydrostatic sample pressure; experimental pressure and temperature must be calibrated. The two assemblies trade sample volume and access against pressure reach rather than one being universally preferable.

A diamond anvil cell concentrates force onto tiny opposing culets, reaching very high pressure with small samples and useful optical access through diamond; its small volume, pressure gradients, alignment demands and difficulties with some heating or sample environments can limit experiments. A multi-anvil press supports a much larger sample and is useful for high-temperature synthesis and bulk measurements, but usually reaches lower ultimate pressures and has more restricted optical access. Hydrostaticity, attainable temperature and calibration depend on the actual apparatus and pressure medium; neither design guarantees uniform pressure.

Stanley Block coauthored a pressure-measurement method using the sharp fluorescence lines of ruby inside a diamond anvil cell. Compression shifts the line energies, allowing a tiny optical marker to report pressure in a region inaccessible to an ordinary mechanical gauge. Calibration turns that spectral shift into a quantitative pressure reading. Line broadening can also reveal departures from uniform hydrostatic compression, so the spectrum contains information about the measurement conditions as well as the mean pressure.^[ref]

A physicist who led crystallographic research and developed ruby fluorescence pressure measurements.^[ref]