Introduction <p>This article contributes to time coincidence gamma-ray spectroscopy in nuclear physics with HPGe detectors. The proposed concept of the measurement apparatus is aimed at studying various effects, including Compton scattering, cascade gamma emissions, backscattering between detectors, Doppler broadening, and X-ray escape measurements.</p> Objectives <p>The coincidence measurements have a significant impact on the observations of these effects, which cannot be explored through single-channel measurements alone. The primary objective is to identify and study these effects.</p> Results <p>The reactions are experimentally acquired with Na-22, Co-60, Cs-137, and Eu-152 isotopes and via a long-term exposition measuring the natural background. The confirmation of these reactions is demonstrated with the use of selected visualization methods. The measurements conducted to determine the timing conditions, related to the charge collection time, are also presented.</p> Conclusions <p>The main novelty of this contribution is the measurement of X-ray escape peaks. The X-ray is generated within the germanium. When it escapes from the detector, it can be captured by the second detector and summed with the photopeak energy. We use the Na-22 source, which simultaneously produces two gamma-rays. The X-ray is subtracted from the photopeak in one detector and added to the full photopeak in another, as shown in the energy spectra. The coincidence condition, along with the selected energy window, is applied to enhance measurements of the X-ray escape peaks.</p>