Relaxation dynamics of charge patches formed inside an insulating capillary by ion impact

International audienceThe dynamics of the charge distribution produced at the inner surface of an insulating capillary by low energy ion impact are investigated theoretically in the case where the entrance, exit and outer capillary surface are grounded. Starting with the surface continuity equation, that describes the charge dynamics at the inner surface, we deduced an analytical solution of the continuity equation in the form of a linear combination of surface charge moments that satisfy the given boundary conditions. We determined the relaxation rate of each moment, which is given as a function of the dimensions and electrical properties of the capillary. We found an approximate expression of the time evolution of the electric potential and field generated by a charge patch during and after beam irradiation. The time evolution of the total charge is also described in detail. Our findings are illustrated with examples