ION SOURCE WITH MODIFIED GAS DELIVERY

摘要

An ion source (100) for producing a beam of ions from a plasma is disclosed. A plasma is created at the centre of an anode (112) by collisions between energetic electrons and molecules of an ionizable gas. The electrons are sourced from a cathode filament 111 and are accelerated to the anode (112) by an applied electric potential. A projection (123) of the anode and a magnetic field having an axis aligned with the axis of the anode act together to concentrate the flow of electrons to the centre of the anode (112). The ionizable gas is introduced into an ionization region (113) of the ion source (100) at the point of concentrated electron flow, either through channels (125) in the side wall of the anode (112) or through a gas delivery tube extending into the ionization region through the open end of the ion source. Ions created in the ionization region are expelled from the ion source as an ion beam centred on the axis of the magnetic field. The anode (112) includes a cavity (127) that receives a cooling fluid.