Integrated laser heating stage with active geometry modulation for simultaneous in situ x-ray transmission and evolved gas analysis of molten liquids.

Investigating the structural evolution of the benefits of high-temperature molten liquids using in situ x-ray transmission measurements with sufficient optical path length and stable temperature control. However, in horizontal beam geometries widely used in laboratories and at synchrotron x-ray facilities, severe wetting and lateral spreading of melts on solid substrates drastically reduce the effective transmission thickness, posing a fundamental limitation to data quality. To address this challenge, a compact, atmosphere-controlled laser-heating platform is developed with a thermocouple-assisted active geometry modulation strategy. Through controlled interaction between the thermocouple probe and the melt, surface tension is exploited to lift the liquid into a stable liquid-bridge configuration, transforming an unfavorable spreading morphology into an optimized vertical transmission cross section while simultaneously enabling direct in situ temperature measurement. The platform integrates a triple-fiber incoherently combined laser head for high optical power density, a closed-loop proportional-integral-derivative temperature control system with steady-state thermocouple-signal fluctuations within ±0.2 °C up to 1200 °C, and an atmosphere-controlled chamber coupled with a quadrupole mass spectrometer for evolved gas analysis. This integrated design enables synchronous acquisition of structural information and chemical reaction under fully molten, non-equilibrium conditions. The performance of the system is demonstrated by in situ x-ray diffraction and gas analysis during firing and vitrification of a multi-component Pb-Ba silicate precursor, where carbonate decomposition, melting, and amorphization are directly correlated in real time.