The Atom Trap Trace Analysis (ATTA) apparatus in Heidelberg offers the unique ability to count the rare argon isotope 39Ar by addressing optical transitions in the atom by laser light of narrow line width. The counting method utilizes the high amount of scattering processes in a magneto-optical trap (MOT) for a distinct capture of the desired isotope alone. In the course of this thesis, the design and realization of a new laser system for ATTA will be presented. Measurements conducted with small sample sizes demonstrated the stability and overall performance of the renewed ATTA apparatus. For the second part of this thesis, the MOT was examined under observation of the more abundant isotope 38Ar. In order to maximize the fluorescence signal, the MOT trapping beams need to be near-resonant to the atomic transition which unfortunately results in a disadvantageous capture efficiency. The introduction of a second trapping laser with a stronger red-detuning, overlying the original MOT beams, improves the loading rate of the trap while maintaining a high scattering rate for detection.