Application of laser pulse heating for the study of high temperature vapours, phase transitions and equation of state

A new dynamic laser pulse heating technique, allowing thermophysical property measurement and equation of state studies above 3000 K has been described. The vapour pressure measurements of uranium oxide up to 5000 K, as required for reactor safety analysis, are presented. The present state of experimental work above the melting point is summarized. A complete survey on predicted critical point data of uranium oxides reviewing the various theoretical models is given. The various dynamic pulse heating techniques are outlined. For a study of the high temperature vapours and the gas dynamic expansion phenomena of the gas jet, the laser surface heating equipment has been extended to include high speed diagnostics such as multichannel spectroscopy, time of flight mass spectrometry, and image converter photography in both the framing and streak recording mode. The evaporation process and thermodynamic interpretation of the data are discussed. A kinetc theory description of the laser induced vapor jet using a monatomic gas dynamic model is given. The optical absorption in the gas jet, giving an upper temperature limit for the applicability of optical pyrometry has been calculated. The reduction of ionization potential was found to be of minor importance.