the condensation column 120 not only changes in an alternating manner between high and low temperatures from one segment to another but the temperature difference also increases in the hot column segments 220 from the input end 120 a to the output end 120 b in the embodiment shown in fig2 the condensation column has a total of seven pairs of cold and hot column segments the temperature difference between the two segments in each pair can be set at 2 u00b0 at the beginning and increases 1 u00b0 per pair the temperature difference in the last pair at the end 120 b is 8 u00b0 this special temperature profile can produce a monotonically increasing supersaturation profile along the center line of the condensation column 120 and can maintain a desired high spatial rate throughout the condensation column 120 without a significant decay near the output end 120 b the flow rate of the aerosol flow in the condensation column 120 also has a significant impact on the supersaturation profile along the center line of the condensation column 120 when the flow rate is not controlled within a proper range the supersaturation profile may not be monotonic but may have the same supersaturation.