CHARACTERIZATION OF H- EXTRACTION FOR A MULTIPOLE ION-SOURCE LOCATED IN THE TAIL OF THE MAGNETIC-FIELD DISTRIBUTION - TYPE-III

A magnetic multipole plasma source and the accelerator for H _ ion source is installed in the distribution of the externally imposed magnetic field which is quasiuniform over the plasma electrode. As the magnetic field of the permanent magnets in this geometry works not only as a so-called magnetic filter for electron cooling, but also as a deflection field to the accompanied beam electrons, there is a possibility for making the fabrication of the H“source simpler/easier due to no use of small magnets in the accelerator. The characteristics of the ion source such as H” extraction, optimization in the magnetic field, the plasma parameters, etc. are investigated. The integrated magnetic flux of 230–320 G cm should be determined by the condition which optimizes the volume production in the source plasma. Achievable current density of H’ is 6 mA/cm2 with 15 keV at the target. Large amounts of the electrons, however, are accelerated altogether to a full energy. They can be stopped with a retarding potential. It is rather unusual that the positive-ion saturation current profile with the probe becomes more like inhomogeneous across the magnetic field. The results (of H_and G cm) are compared with ones for the different three types of the magnet arrangement. © 1994, American Vacuum Society. All rights reserved.