Accuracy and precision of a new microsecond-timescale temperature diagnostic for pulsed-heated diamond anvil cells

The melting temperature of iron and iron alloys at Earth's inner core boundary are crucial information for determining the temperature throughout Earth’s core [1]. The temperature is estimated to be upwards of 5400K [1], but there is little agreement on the actual value due to large uncertainties. As a first step towards more accurate melting curves of iron alloys at megabar pressures, we characterize the precision and accuracy of a newly-built temperature measurement apparatus at Carnegie Earth and Planets Lab. We send 100 to 800 microsecond pulses of energy through ambient-pressure samples of iridium, platinum, titanium, and tungsten, and collect thermal emissions as they melt, using our photomultiplier tube table setup. We find that accuracy is better than 41K, and precision is better than 20K at the known melting temperatures of iridium, platinum, and titanium. The tungsten sample melts at ~ 200 K lower temperature than the literature value, likely due to oxidation in air. These ambient-pressure tests pave the way for improved accuracy during high pressure melting experiments.

[1] Davies, C.J., Cooling history of Earth's core with high thermal conductivity. Physics of the Earth and Planetary Interiors, 2015. 247: p. 65-79.