A space chamber was made for testing the electron bombardment type ion rocket engines. The chamber was evacuated with a 26-inch oil diffusion pump followed by a 6-inch one. The ion beam was accelerated up to 5 kV and the beam current was in the range of 0-100 mA. The gas desorption induced by ion bombardment on the LN cooled wall is mainly discussed. The experimental result is also described on the other problem whether or not the oil diffusion pump is available to use for evacuation of mercury vapor. With cryopumping of the LN cooled wall, ion rocket engine could be operated in the pressure range of 10-6 Torr.
A non-condensing viewing-port window has been developed for vacuum coaters and vacuum metallurgical equipments. The window essentially consists of a transparent Teflon-FEP film heat-sealed on a square glass plate, which is heated by a thin conductive In2O3 film vacuum-deposited on the back side of the glass plate. It has been demonstrated that vapors of most important metal and semiconductor elements and of many compounds do not or scarcely condense on the window when proper conditions are given.