Evolution of the electric potential of an insulator under charged particle impact

Insulating glass capillaries have been shown to lead to ion transmission without any change in either the ion charge state or in the ion kinetic energy. This surprising process has been attributed to a self-organized distribution of charge patches creating the necessary guiding electric potential on the capillary walls. By the use of our original electrometer, it has been possible to measure and monitor simultaneously and in a nondestructive way the electric potential and the transmitted beam intensity during the charging up by an ${\mathrm{Ar}}^{+}$ ion beam. We show that glass microcapillaries can reach potentials higher than 500 V, even in the case of singly charged ions, opening the possibility of high transmission rates and providing a renewed sight into ion beam transport by tapered capillaries. The setup, also suitable for the determination of leakage currents governing the capillary potential dynamics, allowed one to evidence that secondary electrons may strongly affect the rise of the capillary potential and consequently avoid Coulomb blocking of the beam transmission across insulating capillaries.