Johannes Müller’s scientific contributions

We here introduce our cloud chamber which enabled us to grow snow crystals from water vapour under conditions similar to those in natural clouds. The snow crystals grew as a result of water vapour supersaturation as well as due to the interaction of ice crystals and water droplets within the cloud chamber. The cloud chamber, of cylindrical shape with a volume of about 2.7 m 3 , was positioned in a cold room with regulated temperature ranging from −1 to −20°C. A fine mist of water droplets was fed into the cloud chamber and a short pulse of pressurized air triggered the nucleation. Observations of the size and shape distribution of the ice crystals as a function of temperature and supersaturation were consistent with literature values. Different crystal shapes – e.g. plates, columns, hollow columns, dendrites – were successfully formed at different conditions within the chamber. The produced snow was collected at the bottom of the cloud chamber and was used for further experiments and measurements.