The apparatus shown here consists of the grey chamber unit on the right, the brass air pump supported by a retort stand on the left, and a flask and beaker of water mixed with methanol. The floor of the chamber is covered with black velvet soaked in the water and methanol mixture, which is applied with the red pippette. This combination allows the liquid to evaporate easily. When the plunger of the pump is pulled back, some air is drawn from the chamber through the orange rubber hose and the remaining air becomes supersaturated - ie it contains too much vapour. A radioactive source is present in the centre of the chamber, under the black knob seen in the middle of the perspex cover.
Alpha particles radiate from the source in all directions and produce trails of liquid droplets.
A small lamp bulb illuminates the tracks from one side and allows them to be seen more easily from above. The photograph was taken with a tank-like East German SLR camera and a manually timed half second exposure, on 6th December 1988. The source is under the black knob below centre and most of the tracks radiate from it. The track at the top left is probably a background alpha particle from a radioactive atom in air.