In scope of this thesis were different activation methods of gallium-arsenide cathodes tested at the source of spin polarized electrons at the superconducting Darmstadt electron linear accelerator S-DALINAC. The aim of this work was to compare a regular activation with a mask activation. Because of remodeling work to create a third recirculation it was not possible to use high voltage. Therefore all measurements were done at 100 V. The source of spin polarized electrons consists three vacuum chambers. A load lock chamber for the transport of a cathode in the vacuum system, a preparation chamber for the activation of the cathode and the cathode chamber for the generation of a electron beam. With a infrared pyrometer the heat cleaning were calibrated in the load lock and preparation chamber. At a regular activation a vacuum lifetime of 1392,5 ± 176,6 hours and a beam lifetime of 5,455 ± 0,002 hours could determined. A quantum efficiency of 1 µA/mW was reached. The mask activation has unfortunately no satisfying results. Only currents at 80 nA could be extracted with quantum efficiencies at 0,002 µA/mW. Because of that there were no vacuum and beam lifetime determined by mask activation.