Compact hollow cathode ion source with an internal evaporator

A novel construction of a hollow cathode ion source equipped with an internal crucible is presented. The crucible (also known as the evaporator) containing the feeding substance is heated to a high temperature by a hot cathode filament and an arc discharge to enable production of ions from solids. Another crucial feature of the ion source is the proximity of the arc discharge and an extraction opening that enables the production of an intense ion beam even for very low discharge currents (up to 1.2 A). The ion source provides currents of 80 μA (In+), 70 μA (Bi+), 60 μA (Mn+), 50 μA (As+ and Al+) and 35 μA (Sb+) for a typical extraction voltage of 25 kV. The ion source is also able to produce beams of molecular and doubly charged ions (e.g. Sb2+, As2+, Bi2+ and As2+). The time between maintenance breaks is 20–40 h (depending on the feeding substance) making it possible to perform high fluence implantations (1017 ions per cm2) with ions of solids within a single work cycle. The detailed description of the ion source as well as its principle of operation is given. Experimental characteristics i.e. dependencies of extracted beam currents and anode voltage on anode and cathode currents are presented and discussed. The influence of magnetic field flux density on ion source's performance is also shown. A model of ionization in the ion source based on Monte Carlo method is described—some simulation results are shown in order to enrich the discussion.