[en] A calibration source of condensed ^83mKr was built and tested within the frame of this thesis. The energy of the K-32-conversion electrons is fixed due to the energy of the nuclear transition and the binding energy of the K-shell electrons and for that reason it is provided with a natural stability. Alternatively to tritium measurements in the main beamline of the KATRIN experiment and permanently and synchronously at a another MAC-E-Filter (Monitor Spectrometer) this stable electron line can be used as an indicator of the stability of the HV-measurement and spectrometer conditions. ^83mKr is a short living gas with a halflife of T_1/2=1.83 h. To allow a long term monitoring the gas was condensed onto a graphite plate (HOPG). Due to the presence of the substrate the measured line position of the conversion electrons is changed. On the one hand side the work function of the substrate enters, on the other hand side the charge distribution in the substrate recorders itself under the influence of the final state of the conversion process (mirror charge). This leads to an additional binding energy of the ^83mKr⁺, which is transfered to the kinetic energy of the emitted electron. Both the work function and the binding energy of the final state is modified by the presence of residual gas, which is thereby the main cause of instabilities. The aim of this doctoral thesis was to define a film preparation method which leads to a reproducible energy of the conversion electrons. Therefore three methods were tested: cleaning of the substrate with a) a resister by heating, b) by laser ablation and c) preparing a fresh preplating made of stable krypton. Without ablation an ongoing pollution of the substrate appeared which shifted the line position. With ablation 19 films were prepared over the period of one month which showed a stability of 1 ppm. Thereby together with the selection of the cleanest films whose substrate was cleaned by heating, a longterm drift of the voltage divider of 0.61(9) ppm/month could be re-proved. Furthermore the spectrum of the other conversion electron lines of ^83mKr was measured. So the transition energies of the two-step relaxation process of ^83mKr could be determined: E_γ,32=32151,74(35) eV and E_γ,9=9404,71(35) eV. Further rations of the conversion coefficents were estimated. (orig.)