Data on the high-pressure melting temperatures of metals is of great interest in several fields of physics including geophysics. Measuring melt curves is difficult but can be performed in static experiments (with laser-heated diamond-anvil cells for instance) or dynamically (i.e., using shock experiments). However, at the present time, both a Currently at Los Alamos National Laboratory 2 experimental and theoretical results for the melt curve of lead are at too much variance to be considered definitive. As a result, we decided to perform a series of shock experiments designed to provide a measurement of the melt curve of lead up to about 50 GPa in pressure. At the same time, we developed and fielded a new reflectivity diagnostic, using it to make measurements on tin. The results show that the melt curve of lead is somewhat higher than the one previously obtained with static compression and heating techniques.

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Optical pyrometry is widely used in industry and research laboratories to perform surface temperature measurements of sample materials. These shock physics experiments are normally conducted at powder or gas gun facilities or at facilities where high explosives can be used as a shock wave source, and using high-speed pyrometers that are usually calibrated by using a blackbody source. But, electrical power, time, and space can be limiting factors in such facilities, and blackbody calibration can be difficult. Crucial parts of the experimental setup (fibers, lenses, and/or mirrors) are destroyed in such experiments, and the pyrometry system must be recalibrated before each experiment. We have developed a calibration technique using integrating-sphere sources that allows us to calibrate pyrometers more rapidly and easily than with blackbodies. Two different integrating-sphere systems are described to cover the wavelength range generally used in pyrometry studies. The characterization of these systems is fully detailed including measurements of their spectral radiances. A discussion of the advantages and drawbacks of both calibration sources is given.