An ionizing radiation detector has conductive tubes arranged in parallel and containing a pressurized gas mixture, a conductive wire being pulled tight at the center of each tube and capable of being biased with respect thereto. Each tube is divided into isolated longitudinal sections. All the tube sections of a same transverse slice are electrically connected. Each group of sections of a same slice includes means for being connected to an elementary detector, wherein each slice is formed of a grid of blades.