Strategy and enhanced temperature determination in a laser heated diamond anvil cell

We show that a strategy for increased accuracy in temperature determination by optical pyrometry when the wavelength dependence of the emissivity is unknown is to measure the spectral irradiance at short wavelengths. We then introduce an improved method of determining the temperature in laser heated diamond anvil cells. In general a blackbody source is used to determine the optical transfer function required for determining the blackbody curve. By using the thermal radiation of a heated absorber at ambient pressure and known temperature, uncertainties in the temperature determination caused by the wavelength dependence of the emissivity of the heated absorber can be eliminated. Temperature determination reduces to a one-parameter fit to the blackbody curve rather than the usual two parameters (emissivity and temperature), leading to increased precision and accuracy.