Abstract: Some embodiments include operation of an accelerator waveguide to output first particles from a tuned end cavity of the accelerator waveguide at a first energy, detuning of the end cavity, and operation of the accelerator waveguide to output second particles from the detuned end cavity at a second energy.

Abstract: A slow wave structure for coupling RF energy with an electron beam comprises a co-propagating RF section including a plurality of pins having a uniform separation from the plane of an electron beam axis. An output aperture is positioned a half wavelength from a reflection section comprising a change in depth of the pintles, such that RF energy reflected by the change in pintle depth is added to the RF energy traveling with the electron beam. One or more rows of pintles are removed in the region of the output aperture to enhance coupling to the output aperture. The device may include a beam shaper for shaping the electron beam to surround the pintles, and the beam shaper and pintles may share common channels which are longitudinal to the electron beam axis. The slow wave structure may operate in forward and backward wave modes, and may be used in conjunction with other structures to form amplifiers and oscillators.