Development of a Bi+ high current source for heavy ion driven plasma generators

The development of a high current bismuth ion source is motivated by heavy ion driven fusion (HIF) and is part of the conceptual design of a HIF-relevant Bi+ test injector with four beamlets, which could serve as a HIF driver front end element. Envisaged is the development of a 300 mA Bi+ injector that can deliver four parallel beams from a 500 kV platform with 75 mA per beam. The first prototype source is driven by an arc discharge and provides singly charged Bi ions with a fraction more than 92% of the total extracted current. At its perveance limit this source delivers current of 70 mA, with the corresponding voltage being 27.5 kV. The emittance of a 21 mA/18.2 keV beam was measured and it amounted to 0.27 pimm mrad (80%, normalized, 4 root mean square) provided by a seven hole extraction system. Based on these investigations a new ion source will be designed and tested that will deliver current of 75 mA at ion energies up to 65 keV In order to fulfill the requirements of HIF the emittance has to be in the vicinity of 0.4 pimm mrad (normalized). In this article we give a brief description of the design of an advanced ion source. Based on experimental experience using the previous prototype source one major modification made is the construction of an external oven. The use of more than one filament to increase the source lifetime is also planned. (C) 2002 American Institute of Physics.