A method for manufacturing a detector of a first and a second incident ionizing radiation including determining the abscissa em of a point of intersection between a first and a second curve, with the first and second curves representing the evolution of the number of photons or electrical charges generated per second by a transducing material as a function of the total thickness of an amplifying material when the transducing material is irradiated, through this thickness of transducing material, by the first and second incident ionizing radiation, respectively; then selecting the total thickness of amplifying material between 0.9 em and 1.1 em and producing the detector with the selected thickness of amplifying material.