Charge transfer during individual collisions in ice growing from vapor deposition

Measurements of charge transfer during individual collisions between ice spheres and a target growing from vapor deposition have been performed in order to establish the importance of fragmentation in the charging process. It is found that when the target is a few degrees colder than the environment, the charge pulses have mixed signs but the number of positive ones becomes dominant as the target temperature decreases. This behavior is reproduced in collisions with dielectric particles and a target in the same growth conditions. Reversal in the temperature gradient reversed the sign of the charge transfer. Direct evidence of fragments produced during collisions suggests that they are responsible for the measured charge transfer.