Abstract: The present invention relates to ionizing radiation sensors, and, more particularly, to semiconductor spectrometers with thermoelectric cooling, and can most advantageously be used in mineral raw material exploration and evaluation under field conditions. The spectrometer comprises a vacuum chamber with an entrance window for passing the radiation therethrough. The vacuum chamber accommodates a thermoelectric cooler formed by a set of Peltier elements. A heat conducting plate is mounted on the cold side of the thermoelectric cooler, and its hot side is provided with a radiator. Mounted on the heat conducting plate are sets of Peltier elements, integral with the thermoelectric cooler and independent of one another. The Peltier elements of these sets are stacked so as to develop the minimum temperature conditions on one set carrying a semiconductor detector and to provide the maximum refrigeration capacity conditions on the other set provided with the field-effect transistor mounted thereon.