Gyrotron travelling-wave amplifier

A gyrotron travelling-wave amplifier comprising in combination:

• wave-launching means for launching a travelling wave in a preferred mode at a selected frequency .omega.;
• beam-producing means for forming and propagating an annular beam of electrons at relativistic speeds along a path;
• a fast-wave structure, coupled to said wave-launching means and said beam-producing means, wherein said wave and said beam propagate and interact for transferring energy from said beam to said wave, thereby amplifying said wave;
• and
• means for forming a magnetic field B about said beam-producing means and fast-wave structure, said magnetic field having a uniform axial component B.sub.zo in the region of the fast-wave structure and said magnetic field having both an axial component B.sub.zg and a radial component B.sub.rg about said beam-producing means, said axial B.sub.zg and radial B.sub.rg components being chosen so as to form a beam of electrons with a velocity component v.sub..perp., transverse to the axial direction, for causing said electrons to form cyclotron orbits about the axial lines of said magnetic field B.sub.zo, said magnetic field B.sub.zo being chosen for causing said electrons to gyrate in said orbits at a cyclotron frequency .omega..sub.ce given by .omega..sub.ce .times.qB.sub.zo /m, where q and m are the charge and relativistic mass, respectively, of an electron, and where B.sub.zo is of a magnitude such that said selected frequency .omega. of said travelling wave is slightly higher than qB.sub.zo /m+k.sub.z v.sub.z, where k.sub.z is the axial wave number of the travelling wave and v.sub.z is the axial velocity of the electrons.