Transient cataphoresis in a discharge tube with end volumes

A theoretical and experimental study has been made of time-dependent cataphoresis in a binary gas mixture when a dc discharge is initiated in a tube with end volumes behind the electrodes. The theoretical models as proposed by Shair et al. and Metze and Chanin are compared. Transient response curves of the impurity density, computed in accordance with the two models, are presented and discussed. The gas separation in the positive column of a dc discharge is also studied experimentally for a mixture of 0.025% argon in neon. The argon density is monitored at two locations within the positive column of the discharge using a mass spectrometer. The experimental data are compared with calculations based on the model formulated by Metze and Chanin. A good agreement between theory and experiment is obtained for the end-volume configuration under consideration.