Positive phase-velocity tapering of broadband helix traveling-wave tubes for efficiency enhancement

Abstract

A positive phase-velocity tapering of 1.5 octave broadband helix traveling-wave tubes for efficiency enhancement, where the phase velocity is linearly increased in the output section, was studied by using the one-dimensional nonlinear theory. At high frequencies, the electromagnetic wave in the positively tapered section traps the fastest electrons in the decelerating electric field, extracting more energy from the electron beam. At low frequencies, a decreased velocity difference between the electron beam and the electromagnetic wave destroys the phase condition for second-harmonic generation, retaining fundamental wave efficiency as well as reducing its second-harmonic power.

Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report

“…Following Ref. [257] many recent publications have maintained that in the presence of a fourth generation the gauge couplings may unify without supersymmetry (SUSY). However, a closer inspection shows that the fourth generation quark and Higgs boson masses required in this scenario are excluded by experiment [212,[258][259][260]].…”

K_1(1270)-K_1(1400) mixing and the fourth generation SM effects in B-->K_1l^+l^- decays

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Design of a 50Watts level W-band FWG TWT for communication

“…In order to improve the electron efficiency, phase velocity tapering method was often used. Normally, there are two kinds of PVT such as negative and positive PVT [8]. The positive one could increase the efficiency in over octave broadband TWTs.…”