Powerful millimeter-wave generators based on the stimulated Cerenkov radiation of relativistic electron beams

Control of the Operation Mode of a Relativistic <italic>Ka</italic>-Band Backward-Wave Oscillator

“…In addition to the possibility to control the BWO oscillation mode [14], it was shown [24] that for (I b /I st ) ≈ 4, which is optimal for stationary oscillation [25], the transient time of a BWO is defined as τ tr ∝ 1/[1 − (I st /I b ) 1/2 ]; that is, τ tr can be varied by varying the I b /I st ratio. The possibility to vary I st follows from its dependence on the coupling resistance between the beam and the first backward space harmonic of the TM 01 wave (R) and on the length of the SWS (L): [25], and the references therein). The factor ∼L −3 offers a radical way to realize a nonstationary oscillation mode, but this calls for a longer SWS [16]- [18].…”

“…For a given L, the coupling resistance R can be varied in view of its dependence on radius: R = R(r ). Actually, the coupling resistance is determined by the longitudinal component of the synchronous wave electric field at the (tubular) beam radius (r = r b ), and this field decays exponentially from the SWS wall with scaling factor δ ≈ λγβ z /2π [25]. Here, λ is the radiation wavelength, γ is the relativistic mass factor of the beam electrons, and β z is the longitudinal velocity of the electrons normalized for the velocity of light.…”

Method for calculation of helical-waveguide eigenmodes on the basis of solving the equivalent two-dimensional problem by field expansion in circular-waveguide modes

“…In particular, they are used as selective electrodynamic elements such as converters or reflectors of circular-waveguide modes (see, e.g., [1][2][3]). Helical structures are also used or considered for use as electrodynamic systems in various electronic devices [4][5][6][7]. At present, two research lines, in which helically corrugated waveguides play the key role, are intensely worked upon.…”

Mode discriminator based on mode-selective coupling

“…On the basis that the energy of the microwave field can scorch a piece of paper [1] or change the color of thermosensitive paper [2], or break down the gas in a low pressure cell [3], or illumine a neon tube [4], or heat a dielectric target plate to form an infrared picture [5], the image of an electric field structure can be displayed directly. The advantages of this imaging method are visual, simple, and independent of the microwave frequency.…”