A tool for detecting radiation includes a semiconductor detector material that interacts with ionizing radiation, an electrode that collects charge carriers generated in the detector material from an interaction with the ionizing radiation. A shaping circuit forms electrical pulses having a shape that depends on the amount of collected charge. A counting circuit counts the number of pulses and includes a counter and an incrementing element that increments the counter when a comparison parameter exceeds a threshold. The counting circuit further includes a duration-measuring element that measures a pulse duration (f) for each pulse and a peak-detecting element that determines a maximum amplitude (H) of each pulse. A combining element combines maximum amplitude and the pulse duration (f) to establish the comparison parameter. The comparison parameter is the product (H×t) of a maximum amplitude of the pulse and the corresponding pulse duration.