A thermal diffusion chamber for the measurement of cloud condensation nuclei

A static thermal diffusion chamber for the measurement of cloud condensation nuclei (CCN) in the atmosphere was designed and fabricated at the institute. The chamber has a volume of 115 cc. An automatic electronic temperature controller was designed and used with the chamber for regulating the supersaturation in the chamber. The supersaturation in the chamber could be controlled with 2 percent accuracy. The theory relating to the steady state supersaturations in the chamber and the variations in the concentration of CCN under the steady state condition are studied. The details of the thermal diffusion chamber, accuracy of measurement and the result of the observations undertaken at Pune (India) are discussed.