The direct simulation Monte-Carlo method has been used to study the behavior of rarefied vapor flow of aluminum through deposition equipment, where the space between the crucible and the film is surrounded by hood-shaped channels. Aluminum other than that deposited on the film is mostly trapped on the channel walls and recycled. The utilization of aluminum calculated by the simulation is in good agreement with the experimental results.
The breakdown threshold of alumina rf windows depends not only on the bulk characteristics, but also on surface treatments such as polishing and annealing. Sapphire and alumina-ceramic disks, polished and annealed, were examined by high-power tests. The polished disk exhibited a lower threshold value than the annealed one, probably due to its surface charging at defects mechanically introduced by polishing. The elimination of the charged sites present on the surface is considered to be important.