Plasma gun that reduces cathode contamination

A plasma gun comprising

• an evacuatable vessel,
• wall means defining a cathode cavity,
• a cathode and an anode arranged in said evacuatable vessel to produce a connecting plasma and a bombarding plasma jet with said cathode being located in said cathode cavity, said cathode eroding during operating and producing particles of cathode material in said connecting plasma,
• a cooled duct having an inlet port and an outlet port and connected to said cathode cavity at said inlet port, said cathode being arranged in said cathode cavity such that it is laterally offset relative to the inlet port of the cooled duct, and said cooled duct defining the orientation of said connecting plasma,
• a first supply line for a gas stream connected through said anode to form said bombarding plasma jet downstream of said anode, said anode being laterally offset relative to the outlet port of said cooled duct such that a gas discharge duct for said bombarding plasma jet is formed at an angle of approximately 90.degree. with respect to said cooled duct, and
• a second gas supply line that opens into said cooled duct between said inlet port and the outlet port of said cooled duct adjacent said bombarding plasma jet, gas being supplied through said second gas supply line as a substitute for a portion of said cathode material deposited on said cooled duct in order to maintain a substantially constant particle density in said connecting plasma formed between said cathode and said bombarding plasma jet.