Apparatus for accurately measuring the charge distribution, and hence the voltage, on a non-conducting workpiece during ion bombardment. The invention is based on the principal that the charge on the surface of the workpiece induces equal and opposite charge on the surface of an isolated proof plane...http://www.google.es/patents/US4675530?utm_source=gb-gplus-sharePatente US4675530 - Charge density detector for beam implantation
