Spatial acquisition of measurement data over a cross section of a high-energy, high-intensity radiation beam bundle without impairment of measuring accuracy due to saturation or degradation of detectors occurs by imaging an entire cross section of the beam bundle on a shading element, the cross section being separated successively into partial beam bundles having reduced cross sections and reduced intensity through movement of at least one opening, whereby measurement values of the partial beam bundles passing the opening are associated temporally and spatially with positions of the opening.