An experimental and computational study of the secondary electron yield (SEY) of copper foam is presented. Ray-tracing Monte Carlo (MC) simulations, based on primary electron transport and interactions with the electron system in solid and foam-type copper, are also included. The 3D reticulated foam geometry is explicitly represented in the MC model. This allows the influence of the complex copper surface on the energy and angular dependence of the SEY to be determined. Experimental measurements of SEY were performed in a high-vacuum electron gun chamber. Solid copper and copper foam with 100 pores per inch and a 4.6% volume fraction were tested for energy and angular dependence of SEY. Incident angles were varied from 0° to 75° and electron beam energy ranged from 20 eV to 570 eV. The agreement between MC simulations and experiments suggests that a general reduction of the SEY by around 20% is due to the interaction and subsequent adsorption of a fraction of emitted secondary electrons on the internal surfaces of the reticulated foam. Moreover, it is found that the SEY becomes nearly independent of the incident electron energy above 200 eV for steep angles of incidence (θ>45°).

An experimental and simulation-based approach is used to determine the effects of an arc jet plasma on the refractory ceramic material lanthanum hexaboride ([Formula: see text]). 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/[Formula: see text] onto [Formula: see text] 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 [Formula: see text] 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/[Formula: see text] produces a consistent [Formula: see text] melt pool and that an incident heat flux of 19.5 MW/[Formula: see text] results in a 0.11 mm/s surface recession rate.

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The operating temperature window of solid tungsten (W) is dictated by its Ductile to Brittle Transition Temperature (DBTT) and re-crystallization temperature; roughly between 300-1300 °C. The brittleness of W at lower temperatures is exasperated when it undergoes recrystallization. We investigate here the thermal shock resistance of micro-porous W as a meta-material fabricated in a 3D open-cell network structure. We present experimental results for the effects of cyclic high-enthalpy arc-jet plasma on surface damage in three testing categories. Observed damage includes surface ablation of asperities, melting and solidification of W-fuzz on samples that have been exposed to a prior helium plasma, and micro-cracks at ligament triple junctions. Scanning electron microscope (SEM) observations show more micro-cracking on 54% and 23% foams compared to the 43% ones. In all tested samples, thermal expansion/contraction displacements were accommodated by ligament rotation and a network of micro-cracks. No large through-thickness crack were observed.

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