A compact filament-driven multicusp ion source

A compact filament-driven multicusp ion source has been studied using both hydrogen and helium. Three aspects of the source have been investigated: hydrogen ion species, axial energy spread and extractable current. An atomic ion fraction (H+) of approximately 30% could be obtained with a discharge power of 80 V and 3 A. A magnetic analyzer was used to determine the axial energy spread of the extracted (i.e. accelerated) ion beam species, and an electrostatic energy analyzer was used to determine the energy spread of the ions at the source exit. The energy spread of the extracted beam for the individual species of positive hydrogen ions (H+, H-2(+), H-3(+)) and that for the negative hydrogen ions (H-) was measured as well. Energy spreads as low as 2.3 eV were obtained for H+, 2 eV for H-2(+), 1.7 eV for H-3(+), and 1 eV for H-. The axial energy spread in the source exit without extraction for hydrogen and helium was measured to be approximately 1 eV for both cases. The source can generate a hydrogen beam current density of approximately 12 mA/cm(2).