Absolute Instability near the Band Edge of Traveling-Wave Amplifiers

Hung, D. M. H.; Rittersdorf, I. M.; Zhang, Peng; Chernin, D.; Lau, Y. Y.; Antonsen, Thomas M.; Luginsland, J.W.; Simon, David; Gilgenbach, R. M.

doi:10.1103/physrevlett.115.124801

Cited by 36 publications

(15 citation statements)

References 35 publications

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“…On the other hand, the amplifier stability with large signal drive is another important aspect that should be addressed in the future, by accounting for nonlinearities and other practical imperfections. Note that increasing the TWT's length, with end reflections, beyond a critical length can cause the amplifier to enter an absolute instability regime and oscillate (a typical scenario in mismatched TWTs 29,30,46 ). Therefore, DBE amplifiers can be readily designed when careful choices of beam current, length as well as loads are considered, whereas oscillators can also be conceived using different topologies of the DBE cavities.…”

Section: B Giant Gain In Finite Length Structures With Dbementioning

confidence: 99%

Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

et al. 2016

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We propose a new amplification regime based on synchronous operation of four degenerate electromagnetic (EM) modes in a slow-wave structure and the electron beam, referred to as super synchronization. These four EM modes arise in a Fabry-Pérot cavity (FPC) when degenerate band edge (DBE) condition is satisfied. The modes interact constructively with the electron beam resulting in superior amplification. In particular, much larger gains are achieved for smaller beam currents compared to conventional structures based on synchronization with only a single EM mode. We demonstrate giant gain scaling with respect to the length of the slow-wave structure compared to conventional Pierce type single mode traveling wave tube amplifiers. We construct a coupled transmission line (CTL) model for a loaded waveguide slow-wave structure exhibiting a DBE, and investigate the phenomenon of giant gain via super synchronization using the Pierce model generalized to multimode interaction.

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Section: B Giant Gain In Finite Length Structures With Dbementioning

confidence: 99%

Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

et al. 2016

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“…The space charge is accounted for in the evolution of the system vector () z Ψ as described in Eq. (2) in [16], and in Eq. (4) in [17], and is incorporated in the transfer matrix.…”

Section: The Degenerate Band Edge Oscillatormentioning

confidence: 99%

“…Note that the proposed principle of operation is different from the conventional absolute instability in backward wave oscillators [10]- [12]. This principle also differs from traveling wave tube (TWT) operation close to the edge of the Brillouin zone at a regular band edge (RBE) [13]- [16]. Our proposed principle advances a DBE oscillator (DBEO) that relies on synchronization of four Floquet harmonics of four degenerate Bloch modes to the electron beam.…”

Section: Introductionmentioning

confidence: 96%

Low Starting Electron Beam Current in Degenerate Band Edge Oscillators

Othman¹,

Veysi²,

Figotin

et al. 2016

IEEE Trans. Plasma Sci.

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Abstract-We propose a new principle of operation in vacuum electron-beam-based oscillators that leads to a low beam current for starting oscillations. The principle is based on super synchronous operation of an electron beam interacting with four degenerate electromagnetic modes in a slow-wave structure (SWS). The four mode super synchronous regime is associated with a very special degeneracy condition in the dispersion diagram of a cold periodic SWS called degenerate band edge (DBE). This regime features a giant group delay in the finitelength SWS and low starting-oscillation beam current. The starting beam current is at least an order of magnitude smaller compared to a conventional backward wave oscillator (BWO) of the same length. As a representative example we consider a SWS conceived by a periodically-loaded metallic waveguide supporting a DBE, and investigate starting-oscillation conditions using Pierce theory generalized to coupled transmission lines (CTL). The proposed super synchronism regime can be straightforwardly adapted to waveguide geometries others than the periodically-loaded waveguide considered here since DBE is a general property that can be realized in a variety of structures.

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“…Oscillations at the band-edge was analyzed by the investigator recently [12]. Because the Diskon-Rod TWT is overmoded, oscillations are the major concern.…”

Section: Discussionmentioning

confidence: 99%

Traveling Wave Amplifier Driven by a Large Diameter Annular Electron Beam in a Disk-Loaded Structure

Lau¹

2015

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Absolute Instability near the Band Edge of Traveling-Wave Amplifiers

Cited by 36 publications

References 35 publications

Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

Low Starting Electron Beam Current in Degenerate Band Edge Oscillators

Traveling Wave Amplifier Driven by a Large Diameter Annular Electron Beam in a Disk-Loaded Structure

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