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

TL;DR

DIMOHA is a novel time-domain Hamiltonian-based algorithm for simulating traveling-wave tubes, offering faster computation, flexibility in waveform types, and accurate modeling of nonlinear and harmonic phenomena.

Contribution

It introduces a Hamiltonian approach that improves speed, flexibility, and accuracy over traditional PIC and frequency methods for TWT simulations.

Findings

DIMOHA accurately simulates TWT behaviors compared to measurements.

It handles arbitrary waveforms, including CW and digital modulations.

The algorithm is significantly faster than PIC codes.

Abstract

To simulate traveling-wave tubes (TWTs) in time domain and more generally the wave-particle interaction in vacuum devices, we developed the DIscrete MOdel with HAmiltonian approach (dimoha) as an alternative to current particle-in-cell (PIC) and frequency approaches. Indeed, it is based on a longitudinal N-body Hamiltonian approach satisfying Maxwell's equations. Advantages of dimoha comprise: (i) it allows arbitrary waveform (not just field envelope), including continuous waveform (CW), multiple carriers or digital modulations (shift keying); (ii) the algorithm is much faster than PIC codes thanks to a field discretization allowing a drastic degree-of-freedom reduction, along with a robust symplectic integrator; (iii) it supports any periodic slow-wave structure design such as helix or folded waveguides; (iv) it reproduces harmonic generation, reflection, oscillation and distortion phenomena; (v) it handles nonlinear dynamics, including intermodulations, trapping and chaos. dimoha accuracy is assessed by comparing it against measurements from a commercial Ku-band tapered helix TWT and against simulations from a sub-THz folded waveguide TWT with a staggered double-grating slow-wave structure. The algorithm is also tested for multiple-carriers simulations with success.