A nuclear physics detector is sensitive to Alpha, Beta and Gamma rays and to thermal neutrons; it comprises a semi-conductor crystal fitted with its parallel faces between two electrodes and resting on a flexible contact element situated between the first electrode and a conducting disc which bears against and is sepd. from the base plate of the unit by means of an insulating plate; a coaxial cable passes through the base plate and has its central pole connected to the conducting disc; the crystal is centered and mounted in a conducting housing screwed onto the base plate and having a seal of elastic matl. between the upper flange or rim of the housing, into which a window is mounted, and the second electrode; the semi-conductor crystal is of cadmium telluride (CdTe) having a high specific resistance. The elastic element is pref. a woven underlay of gilt bronze wire. As a semi-conductor detector, the crystal reacts to Alpha, Beta and Gamma rays by detecting the pairs of electron holes formed by the incident radiation and directly detecting the thermal neutrons formed by the nuclear reaction generated inside the counter itself. The detector is thus sensitive to all four kinds of radiation.
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