An apparatus includes a conductive structure and an insulated conductor disposed proximate an exterior portion of the conductive structure to modify an electric field about the conductive structure. The insulated conductor has an insulator with a dielectric strength greater than 75 kilovolts (kV)/inch disposed about a conductor. An ion implanter is also provided. The ion implanter includes an ion source configured to provide an ion beam, a terminal structure defining a cavity, the ion source at least partially disposed within the cavity, and an insulated conductor. The insulated conductor is disposed proximate an exterior portion of the terminal structure to modify an electric field about the terminal structure. The insulated conductor has an insulator with a dielectric strength greater than 75 kV/inch disposed about a conductor.