Mechanically tunable magnetron injection gun (MIG)

A mechanically tunable magnetron injection gun, comprising:

• a ring-shaped electron emitter for producing a hollow annular electron beam;
• said ring-shaped electron emitter embedded in a stainless steel outer electrode;
• a center electrode surrounded by said ring-shaped electron emitter;
• said outer electrode, said ring-shaped electron emitter and said center electrode providing a cathode assembly;
• said cathode assembly being a part of said mechanically tunable magnetron injection gun;
• said outer electrode, said ring-shaped electron emitter, said center electrode and said cathode assembly all aligned to a common center axis and providing a cathode assembly configured to be axially symmetric about said common center axis;
• a magnetic field oriented parallel to said common center axis;
• said ring-shaped electron emitter emitting a hollow annular electron beam, the center of said hollow annular electron beam aligned with said common center axis, said annular electron beam characterized by an electron beam quality and a transverse-to-axial velocity ratio;
• a linear motion feedthrough connected with a high vacuum weld to a vacuum flange, said vacuum flange bolted onto a base plate to provide a high vacuum connection, a ring brazed to a ceramic insulator, said ring also connected with a high vacuum weld to said base plate, a corona ring fit around said ring, a vacuum container side wall brazed to said ceramic insulator, a vacuum pump for extracting air through a pumping port passing through a vacuum container side wall, a vacuum container bolted to said vacuum container side well to provide a high vacuum fit, an anode fitted into said vacuum container;
• a stem welded to said vacuum flange, said stem extending within said ceramic insulator, said linear motion feedthrough extending within said stem and extending along said common center axis;
• said linear motion feedthrough connected to a sliding shaft also aligned along said common center axis, said linear motion feedthrough held in position along said common center axis by linear ball bearings fit against inner walls of said stem;
• said sliding shaft attached to said center electrode;
• said linear motion feedthrough moving said sliding shaft along said common center axis in response to turning a knob attached to said linear motion feedthrough, wherein said sliding shaft is constrained to purely axial motion along said common center was by means of said linear ball bearings, wherein turning said knob results in purely axial motion of said center electrode along said common center axis and wherein sad purely axial motion of said center electrode along said common center axis is directly proportional to the rotation of said knob;
• said center electrode moving purely axially along said common center axis within a hollow region inside of said hollow annular electron beam to tune said hollow annular electron bean from inside said hollow region thereby increasing said electron beam quality and sad transverse-to-axial velocity ratio of said hollow annular electron beam.