Controlled automated inlet of minute quantities of oxygen to activate photocathodes



For the new high- intensity experiments at MESA (Mainz Energy-Recovering Superconducting Accelerator) a remote-controlled mechanism for admitting minute quantities of oxygen into ultra-high vacuum is needed. For this purpose, the thermally controlled diffusion of oxygen from the air through thin silver walls is to be used.


A thin-walled small silver tube is heated by a remote-controlled power source. Because of the strong temperature dependence of the diffusion through silver at a temperature of about 600 degrees Celsius, pure oxygen diffuses through the silver wall in measurable amounts. This can be detected with a mass separator, which is tuned to the molecular mass of oxygen. Specifically, it is to be assessed whether other gases are released, which can also be detected by the mass separator.