Using the electrolytical etching method the breakthrough-times (i.e. the time when the two etched cones from both sides of the detector contact) and the resulting track etching rates v(t) of heavy ion tracks in 8 mu m polycarbonate Makrofol KG have been measured. The samples were irradiated at the GSI, Darmstadt (Germany) with gold ions and different fluences at a specific energy of 11.6 MeV/u. All foils were etched in 6 n NaOH at room temperature. Fluctuations of breakthrough-times of single pore foils were analysed. Also the breakthough-times of multi-pore-foils were measured. The dependence of the mean breakthrough-time on the ion fluence is dicussed. This dependence will be explained by the fluctuations of the breakthrough-time of the pores.
