DEVELOPMENT OF TECHNOLOGICAL SOURCES OF GAS IONS ON THE BASIS OF HOLLOW-CATHODE GLOW-DISCHARGES

Design principles and basic properties of broad-beam gas ion sources b ased on a low-pressure glow discharge are discussed. It is shown that properties of the discharge in a coaxial electrode structure with a ho llow cathode and a rod anode in a magnetic held favor its use in sourc es of gas ions. Two main types of ion sources using this electrode str ucture are described. Application of a weak magnetic field facilitates igniting of the discharge, ensures stable running of high-current dis charges under low gas pressures, and provides for formation of a homog eneous plasma. These conditions are realized in an inverted magnetron- type electrode system with ion extraction from the plasma generated in the cathode part of the discharge. The discharge with a strong magnet ic field in the cathode region, which is used in a plasmatron-type ele ctrode system with extraction of ions from the anode plasma, gives imp roved gas and energy efficiency of the ion source. The discharge ignit ion and operation conditions, ion-emission properties and mass-charge composition of the plasma, contamination of the plasma as a result of the cathode sputtering in the glow discharge, features specific to ext raction of ions and beam formation by an electrostatic ion-optical sys tem are analyzed and compared for these two structures. Glow-discharge gas ion sources generate broad ion beams with a 5-200 cm(2) cross-sec tion and an energy of 1-50 keV under pulsed and continuous regimes. Th e beam current density is from 10 mu A/cm(2) to 10 mA/cm(2). (C) 1997 Elsevier Science S.A.