Separated ion source

A high current separated ion source comprising:

• means for producing along a path a high aspect ratio substantially rectangular ribbon ion beam of substantially rectangular cross section and having a height and a thickness;
• magnetic field means for producing a magnetic field in the direction of the height of the beam across said path;
• first and second separator electrodes positioned on opposite sides of said path laterally of said path in the thickness dimension of the beam for applying an electric field across said path, said separator electrodes being positioned with respect to said magnetic field means so that said electric field is transverse with respect to said magnetic field to separate unwanted ion species laterally from the ion beam;
• said means for producing a ribbon ion beam comprising a cylindrical tubular cathode electrode and a central anode electrode therein, for defining a plasma discharge space within said cathode and around said anode which contains gas to be ionized and through which electrons pass to ionize the gas, said means for producing a magnetic field also producing a magnetic field in said discharge space to lengthen the electron path in said discharge space to produce a Penning discharge;
• walls defining a narrow rectangular slot opening in said cathode electrode through which ions are extracted to form the high aspect ratio substantially rectangular ribbon ion beam, said slot opening in said cathode electrode being oriented in a direction parallel to the axis of said cylindrical cathode;
• and
• an accelerator electrode positioned adjacent to the beam path to accelerate ions which have been extracted from said cathode slot along the beam path so that a separated ion beam having an ion current above 100 microamperes is formed.