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Part I shows that quantitative measurements of heat capacity aretheoretically possible inside diamond anvil cells via high-frequency Jouleheating (100 kHz to 10 MHz), opening up the possibility of new methods todetect and characterize transformations at high-pressure such as the glasstransitions, melting, magnetic orderings, or the onset of superconductivity.Here we test the possibility outlined in Part I, using prototypes and detailednumerical models. First, a coupled electrical-thermal numerical model showsthat specific heat of metals inside diamond cells can be measured directlyusing $\sim 1$ MHz frequency, with $< 10%$ accuracy. Second, we test physicalmodels of high-pressure experiments, i.e. diamond-cell mock-ups. Metal foils of2 to 6 $\mu$m-thickness are clamped between glass insulation inside diamondanvil cells. Fitting data from 10 Hz to $\sim 30$ kHz, we infer the specificheat capacities of Fe, Pt and Ni with $\pm 20$ to $30%$ accuracy. Theelectrical test equipment generates -80 dBc spurious harmonics which overwhelmthe thermally-induced harmonics at higher frequencies, disallowing the highprecision expected from numerical models. An alternative Joule-heatingcalorimetry experiment, on the other hand, does allow absolute measurementswith $< 10%$ accuracy, despite the -80 dBc spurious harmonics: the measurementof thermal effusivity, $\sqrt{\rho c k}$ ($\rho$, $c$ and $k$ being density,specific heat and thermal conductivity), of the insulation surrounding athin-film heater. Using a $\sim 50$ nm-thick Pt heater surrounded by glass and10 Hz to 300 kHz frequency, we measure thermal effusivity with $\pm 6%$accuracy inside the sample chamber of a diamond anvil cell.

Modulation calorimetry in diamond anvil cells II: Joule-heating design and prototypes