What is "diamond anvil cell"

n. A device that is used to subject small samples of materials to exceptionally high pressures

A diamond anvil cell (DAC) is a high pressure device used in scientific experiments. It allows compressing a small (sub- millimeter-sized) piece of material to extreme pressures, typically up to around 100-200 gigapascals, although it is possible to achieve pressures up to 770 gigapascals (7,700,000 bars / 7.7 million atmospheres).

The device has been used to recreate the pressure existing deep inside planets, creating materials and phases not observed under normal conditions. Notable examples include the non-molecular ice X, polymeric nitrogen and metallic xenon (an inert gas at lower pressures).

A DAC consists of two opposing diamonds with a sample compressed between the culets (tips). Pressure may be monitored using a reference material whose behavior under pressure is known. Common pressure standards include ruby fluorescence, and various structurally simple metals, such as copper or platinum. The uniaxial pressure supplied by the DAC may be transformed into uniform hydrostatic pressure using a pressure transmitting medium, such as argon, xenon, hydrogen, helium, paraffin oil or a mixture of methanol and ethanol. The pressure-transmitting medium is enclosed by a gasket and the two diamond anvils. The sample can be viewed through the diamonds and illuminated by X-rays and visible light. In this way, X-ray diffraction and fluorescence; optical absorption and photoluminescence; Mössbauer, Raman and Brillouin scattering; positron annihilation and other signals can be measured from materials under high pressure. Magnetic and microwave fields can be applied externally to the cell allowing nuclear magnetic resonance, electron paramagnetic resonance and other magnetic measurements. Attaching electrodes to the sample allows electrical and magnetoelectrical measurements as well as heating up the sample to a few thousand degrees. Much higher temperatures (up to 7000 K) can be achieved with laser-induced heating, and cooling down to millikelvins has been demonstrated.