Wide-band gyrotron traveling-wave amplifier

A wide-band gyrotron traveling wave amplifier comprising:

• a tapered waveguide wherein the cross-section thereof gradually increases from a small first end thereof to a larger second end for propagating electromagnetic energy therein;
• means for generating a beam of relativistic electrons with helical electron motion, and applying this beam to said small first end of said tapered waveguide to propagate in the axial direction therein;
• means for generating a tapered magnetic field B within said waveguide in a direction approximately parallel to the axis of said waveguide with a profile closely in accordance with the following equation:
• ##EQU5## where B.sub.o is the axial magnetic field at the small first end,
• .gamma.=(1-V.sub..perp..sup.2 /C.sup.2 -V.sub.z.sup.2 /C.sup.2).sup.-1/2
• .gamma..sub.zo =(1-V.sub..perp.o.sup.2 /C.sup.2 -V.sub.zo.sup.2 /C.sup.2).sup.-1/2
• .beta..sub..perp.o is the electron velocity perpendicular to the magnetic field at the small first end of the waveguide divided by c,
• .lambda..sub.w is the cutoff wavelength of said tapered waveguide,
• .lambda..sub.wo is the cutoff wavelength of said tapered waveguide at the small first end thereof,
• V.sub..perp. is the electron velocity perpendicular to the waveguide axis,
• V.sub..perp.o is the electron velocity perpendicular to the waveguide axis at the small first end of said waveguide;
• V.sub.z is the electron velocity parallel to the waveguide axis,
• V.sub.zo is the electron velocity parallel to the waveguide axis at the small first end of said waveguide;
• and
• means for launching an input electromagnetic wave at said larger second end of said waveguide to propagate toward said small first end such that the frequencies in the input wave will be reflected at various points along the constriction of said tapered waveguide so that they copropagate with said electron beam and are amplified thereby.