Transportprozesse von K+- und Cs+-Ionen durch Porositäten in freistehenden Poly(para)Xylylen-Membranen

We describe the experimental setup and investigation of the transport of alkali ions through poly(para)xylylene membranes. It consists of an ion source where a continuous beam of alkali ions is generated from a surface emitter. Via ion-optics the ions are guided to an middle chamber where the ion beam can be deflected via an pulsed voltage at a system of deflection plates to create an pulsed ion beam. The ions are then guided into the main chaimber where the interactions with the free-standing mambranes of variable thickness is investigated as a function of the impact energy. The transport of the alkali ions most likely proceeds through pores or porosities in the mambranes and is observed at an impact energy of several hundret volts. At the highest impact energies empolyed (around 2000eV) the transmission of secondary electrons is observed, most likely due to collision processes causing kinetic electron emisssion.