High power gyrotron (OSC) or gyrotron type amplifier using light weight focusing for millimeter wave tubes

Claim 1

A microwave gyrotron tube comprising: an evacuated elongated chamber; a cathode located at one end of said chamber; an injection gun located at said one end of said chamber including means for injecting a hollow, circular cylindrical electron beam into said chamber coaxial with the principal longitudinal axis thereof; a solenoid means mounted around said tube for providing a longitudinal magnetic field in said chamber for focussing said electron beam; said chamber including at least one r-f input cavity mounted in the path of said beam and said cavity having means for coupling r-f gyrotron energy to said beam; the other end of said tube including a means for collecting said electron beam and a means for coupling microwave energy out of said tube; at least one strong-field quadrupole magnetic means in said chamber adjacent to said electron beam and located between said injection gun and said cavity for reshaping said electron beam into a hollow elliptical electron beam; and said quadrupole magnetic means including four magnets having poles extending into said chamber adjacent to said electron beam and being symetrically spaced about said beam in a plane perpendicular to said longitudinal axis with the adjacent ones of said poles having opposite polarities.