A mixture of methanol and ethanol in a 4:1 volume ratio has good physical properties for use in these devices. William Bassett invented a “hydrothermal” type of these devices for use with fluids. Conditions in these devices are usually analyzed either with X-ray diffraction on a material whose equation of state is known, or by measuring shifts in the fluorescence lines of ruby. A now-retracted 2020 Nature paper claimed to use these devices to achieve room-temperature superconductivity in a carbonaceous sulfur hydride. In these devices, a tungsten or rhenium (*) gasket encloses the sample, which must be smaller than a few hundred microns, since these devices create a very small area to transmit a large force. For 10 points, what devices generate millions of atmospheres of pressure by squeezing a sample between two minerals with Mohs hardness 10? ■END■
ANSWER: diamond anvil cells [accept DAC, prompt on diamond anvils by asking “What's the full name of the device that uses those?”] (I have had to edit the clue about the Dias Nature paper multiple times due to updates in the saga, which appears to be at the “attempting to defraud investors” phase: https://www.science.org/content/article/something-seriously-wrong-room-temperature-superconductivity-study-retracted)
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= Average correct buzz position