On the Natural Decay of Corona Charged Teflon Sheet

The surface potential of teflon charged by a negative corona decays faster than the potential of samples charged to the same level in vacuo by an electron beam. This motivated our attempt to reinvestigate the mechanism of the charge decay in air. The samples were corona charged on a grounded substrate, then transferred with their substrate onto an open Faraday cup, the sample facing an electrode connected to the input of an electrometer. With this set-up, it was possible, by simple electrostatic argumentation, to ascribe the decay either to migration of charges to the substrate through the sample (or along its surface), or to ionic conduction in the air gap between the charged sample and the measuring electrode. It was shown that the latter process actually dominates in the early phase of the decay.