Ultra-High Vacuum Evaporators Employing Getter-Ion Pumps

Pump-down curves of evaporators employing getter-ion pump are described.One type of evaporatore (A) is equipped with a 125 l/s getter-ion pump but not a separation valve, and the other one (B) is equipped with a 400l/s getter-ion pump and a separation valve of 150 mm in diameter. Although the bell-jar in the former apparatus is made of stainleas steel and the latter one is made of glass, Viton-A gaskets of L-type in section are used for sealing in both systems.Pump-down curves are measured on these two types of evaporators under the following three conditions : (1) unbaked (2) baked out in vacuum atmosphere, and (3) baked out at atmospheric pressure. Without bake-out, the pressure of 1×10-7 mmHg is attained even in about 7 hours-pumping, whereas baking-out all the system makes it possible to attain the pressure lower than 3×10-9 mmHg. The separation valve which keeps getter-ion pump always in vacuum improves the pump-down curves evidently without baking.Results are summarized as follows : (1) In order to obtain ultra-high vacuum in the range of 10-9 mmHg, baking out the whole system is indispensable.(2) in order to obtain the pressure in the range of 10-8 mmHg as fast as possible, the application of separation valve is required.