| CPC H01J 37/08 (2013.01) [H01J 2237/0807 (2013.01)] | 11 Claims | 

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               1. A gas ion gun comprising: 
            a main chamber in which is introduced a gas to be ionized, 
                an anode electrode to remove electrons from the gas in order to create gas ions, the anode electrode comprising a wire made of an electrical conductive material or of a semiconductor material, the wire extending along a longitudinal axis from a proximal end to a flattened distal end and the flattened distal end being housed inside the main chamber, 
                a cathode to create an ionizing electric field which is greater than 10V/nm in a region near the flattened distal end of the wire, 
                wherein the anode electrode further comprises a crystal particle directly deposited on the flattened distal end, the electrical conductivity of the crystal particle being ten times smaller than the electrical conductivity of the wire. 
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