Mass loss, sublimation, and surface damage of lanthanum hexaboride in an arc jet plasma

Abstract

An experimental and simulation-based approach is used to determine the effects of an arc jet plasma on the refractory ceramic material lanthanum hexaboride (LaB6). Experiments are performed at the High Energy Flux Test facilitY (HEFTY) located at UCLA. An SG-100 plasma jet generates an argon plasma into a vacuum chamber and imparts a maximum heat flux of 19.5 MW/m2 onto LaB6 disks. Heat flux results are calibrated using a combination of thermocouple data as well as multiphysics numerical simulations in COMSOL, which aim to replicate the testing environment. Moreover, material characterization tools including scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and optical profilometry are used to better understand the mechanisms by which LaB6 loses mass through evaporation, sublimation, and surface damage during an arc jet exposure. It is determined that a minimum energy fluence of 200–300 MJ/m2 produces a consistent LaB6 melt pool and that an incident heat flux of 19.5 MW/m2 results in a 0.11 mm/s surface recession rate.