PRELIMINARY-RESULTS OF A BROAD-BEAM RADIO-FREQUENCY ION-SOURCE WITH ELECTRON-PLASMA INTERACTION

A new design of a broad beam rf ion source is made to deliver currents of 100 mu A-30 mA with extraction voltages of 200 V-2 kV. Its plasma intensifying system is made with both the addition of electrons from a n immersed filament in the discharge and an axial magnetic field of 70 -300 G. Uniform beam density distribution is made with a planner graph ite cathode which has a number of holes of varying diameters arranged to produce perveance matching with the normal Gaussian distribution of the beam density. Variations of the output currents are studied with variations of extraction voltage, magnetic field intensity, discharge pressure, and electron injection into the plasma. The influence of ele ctron injection into the plasma is found to have a great effect on inc reasing the extracted current to about four times its value without el ectron injection. The increase of extraction voltage is limited to the use of electron injection at V-ex > 2 kV due to the presence of break down inside the discharge tube. (C) 1996 American Institute of Physics .