Demonstrates the ionizing effect of the radioactive emissions. A long narrow metal strip is mounted on edge parallel to and underneath a wire mesh, together form two long conductors with a narrow air gap insulation between them and are provided with a 4mm socket terminals for power input. On applying high voltage across the terminals, a continuous spark along the length of the wire mesh is produced. The radioactive material source is located on the wire mesh while use. Complete assembly housed in a insulated moulded plastic box (240x130x40) mm approx. Operating voltage for the instrument is 5 to 6 kv.