The Superconducting Fragment Separator (Super-FRS) will be built as part of the Facility of Antiproton and Ion Research (FAIR). For the slow-extraction part of the
beam diagnostics system a total of 36 detectors are needed for the beam monitoring, tracking and characterization of the produced ions. GEM-TPC
detectors are planned to be used for the diagnostics at slow extraction mode of the separator. The detectors will be placed in focal planes along the separator. Simulations have been made to study the effects of the detector materials and geometries in order minimize their influence to the performance of the separator. Results of these simulations are presented in this paper.