= Solution
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.
\Image[/past-exam-of-the-materials-science-course-of-the-university-of-cambridge/2015/paper-1-pressure-cells.png]
{title=Original conceptual comparison of multi-anvil load transmission and opposed diamond culets, showing confinement and qualitative heating/access tradeoffs}
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