Development of a Bi+ source for heavy ion fusion

A volume source based on the high efficiency source is being developed for heavy ion production. Bismuth was chosen for exemplifying investigations because of its low melting point. The ion source is driven by an are discharge ionizing bismuth atoms which are evaporated from an oven inside the source chamber. It has been optimized to produce a beam with a fraction of singly ionized bismuth above 92%. A multiaperture extraction system was built consisting of seven holes with a radius of 3 mm each. For that system, the perveance limit was achieved at a beam current of 70 mA and an extraction voltage of 27.5 kV. The corresponding emission current density amounts to 35 mA/cm(2). This value was obtained for an are power of only 280 W. Furthermore, the emittance of a beam extracted from the multiaperture extraction system has been determined with a high power emittance scanner. It amounts to 0.27 pi mm mrad (80%, normalized, 4 rms). In this case, the emittance of a single beam is 0.017 pi mm mrad. This article will give a detailed description of both the source and the experimental setup. In addition, various dependencies between the plasma parameters and the beam composition are presented. (C) 1998 American Institute of Physics.