Magnetron

A magnetron comprising:

• a cylinder forming an anode electrode;
• a plurality of vanes extending radially and inwardly from the inner wall of said anode electrode cylinder;
• two pairs of inner and outer strap rings, said inner strap rings electrically connecting every second one of said vanes at the ends thereof in the axial direction of said anode electrode cylinder, said outer strap rings electrically connecting remaining ones of said vanes at the ends thereof in the axial direction of said anode electrode cylinder, said outer strap rings being located at a position further out than said inner strap rings with respect to the axis of said anode electrode cylinder;
• a cathode filament having a lead-out wire and disposed substantially at the center of said anode electrode cylinder, an interaction space formed by a d.c. electric field produced between said anode electrode and said cathode filament and a magnetic field intersecting at right angles with said electric field being defined by the edges of said vanes in the radial direction of said anode cylinder;
• magnetic members provided at both ends of said anode cylinder and adapted to introduce an external magnetic field into said interaction space so as to establish said intersection magnetic field;
• a conductor having one end connected to one of said vanes to lead out a generated microwave;
• a metallic sleeve-like structure having a pair of openings, one of said openings being fixed to said anode cylinder at the end thereof where said conductor is provided, the other opening serving to lead out said conductor to the outside, said conductor extending in a certain length from said other opening of said structure;
• first sealing means of insulation material for sealing said other opening of said sleeve-like structure inclusive of said conductor, a microwave output being emitted to the outside from a section of said conductor located inside of said first sealing means;
• and
• second sealing means for sealing hermetically said anode cylinder inclusive of said lead-out wire at the end of said anode cylinder where said lead-out wire is provided, said inner and outer strap rings having diameters determined on the basis of a relation between an algebraic mean of diameters of said inner and outer strap rings and an attenuation value of a spurious microwave to be prevented from leaking, said inner and outer strap rings have diameters determined such that the algebraic mean of diameters of said inner and outer strap rings is substantially 1.75 to 1.95 times the diameter of said interaction space.