PCT No. PCT/FR 78/00046 Sec. 371 Date Aug. 2, 1979 Sec. 102(e) Date Aug. 2, 1979 PCT Filed Dec. 7, 1978 PCT Pub. No. W079/00353 PCT Pub. Date June 28, 1979 A device for detecting and localizing soft gamma and X radiations, comprising an enclosure 10 provided with a window 11 opaque to light and transparent to incident radiations, occupied by a noble gas and provided with electrodes for causing the electrons to drift towards a secondary photon creation space. In said space there reigns an electri...