Entrapment pump: Noble gas pump for use in combination with a getter pump

Abstract

A new type of minicapture pump which acts on noble gas species and operates in combination with a getter pump has been developed. We call it the “entrapment pump.” The pump is a single Penning cell (φ7×h5 mm anode) whose cathode can be heated during pumping to more than 1000 °C. After the getter pump is working, the pump cathode is activated by heating. Then, in a second step, the pump is operated by applying the high voltage and residual noble gas (argon) pumped by burial, not sputtering. Weakly buried noble gas within the pump cell is re-emitted by intentional heating. This is performed during every pumpdown following any exposure to atmospheric air and the surface of the cathode is thereby cleaned and renewed. As a result, noble gas atoms are buried in a pure metal surface when high voltage is applied and no burst of contamination species is generated from the cathode surface when the pump is initially started. The re-emission of previously pumped noble gas, acting as a gas source, is also minimized for low pressures. The pumping speed of the entrapment pump remains constant in the 10−8 Pa range. Therefore, the entrapment pump should be useful in attaining ultrahigh vacuum and extreme high vacuum in combination with getter pumps such as evaporable barium getters or nonevaporable getters.