In a power control apparatus for controlling power supply of an ion source having an indirectly headed cathode, the cathode bias power supply which provides a bias potential between the filament and cathode has an output that is effected by changes in impedance of the electron flow in the region between...http://www.google.de/patents/US6259210?utm_source=gb-gplus-sharePatent US6259210 - Power control apparatus for an ION source having an indirectly heated cathode
