Efficient Time-Domain Simulations of a Helix Traveling-Wave Tube

Theory and New Amplification Regime in Periodic Multimodal Slow Wave Structures With Degeneracy Interacting With an Electron Beam

“…The electron beam is assumed to propagate along the +z direction. The lengths of the segments 12 [45], [46]. The electron beam is described as in [42], [42], [47], where / em   11 1.759 10 [C/kg]  denotes the charge-to-mass ratio of the electron with charge equal to e  and m is the electron mass.…”

“…The two anisotropic layers had in-plane anisotropy with two different orientations of the optical axes, say the main axis is oriented along 1  and 2  in two contiguous layers, respectively. The angle 12     defines the optical axis misalignment between two layers.…”

“…The choice of the SWS is critical for best operation of the TWT. The helix is a popular SWS that has been used due to the its simplicity of construction, large interaction impedance and wide operating bandwidth [10]- [12]. Apart from the helix, periodic structures mainly made up of coupled cavities or slots have previously been utilized as SWS in TWTs [8], [13], [14].…”

DIMOHA: A Time-Domain Algorithm for Traveling-Wave Tube Simulations

“…Coupling terms Ω n−n between cells n and n are obtained from the Fourier series of the dispersion relation ω(β) = N ph n=−N ph Ω n e inβd , with β the wavenumber (propagation constant). We take the range of coupling N ph , estimated in [17], at 5 for helix TWTs and 1 for folded waveguides. To take into account any pitch tapering, coupling terms are recomputed at each different cell.…”

“…As the discrete model decomposes only the circuit part of fields, it misses the space charge field. For N e macroelectrons, the axial space-charge field in one dimension E sc (q k ) = − Ne k =k ∂ z φ sc (q k − q k ) follows Rowe's model [17,26]…”