Development of a High-Current Helicon Ion Source With High Monatomic Fraction for the Application of Neutron Generators

A high-current helicon ion source has been developed for neutron generator application. High-density plasmas with high electron temperatures are generated by launching helicon waves with a half-helical antenna in various magnetic field configurations. Helicon plasmas with high power efficiency are favorable in building ion sources with high current density and high monatomic ion beam fraction that are required for compact neutron generators. A maximum hydrogen beam current of 50 mA is extracted at 34 kV from the helicon plasma source with 1.9-kW RF power at 13.56 MHz. High current densities of 212 mA/cm
²
and high atomic fractions of up to 94% are achieved with this source. These measured beam parameters are mostly consistent with plasma parameters, except for unusually high monatomic beam fraction, which may be due to the existence of energetic electrons in helicon plasmas.