A device for detecting and locating radiations, comprising at least one cathode brought to a first potential with respect to a reference potential in a sealed enclosure, a plurality of threadlike anodes insulated from one another and photosensitive means, said enclosure being provided with a port-hole transparent to the radiations involved, situated in register with said cathode and anodes, said device further comprising an insulating support with two faces, a portion of one of said two faces, situated in register with said port-hole, being coated with a layer of a conductive material forming a mesh network constituting said cathode, the extremities of said anodes being in the shape of a point and the axes of said anodes respectively coinciding with the axes of the meshes of said network, these points being recessed with respect to the insulating support face, coated with the network conductive meshes.