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We present two algorithmic improvements to enhance accuracy for large-signal simulations of vacuum electronic amplifiers using the GPU-accelerated, 3D time-domain particle-in-cell code “Neptune”. A new conformal (cut-cell) geometry model with a new algorithm for Ohmic surface loss accurately predicts the dispersive and dissipative electromagnetic properties of complex metal device structures.
A three-dimensional (3-D) large signal model of beam-wave interaction in a folded waveguide (FW) slow wave circuit is described. The 3-D code carries out with numerical solutions of the structure, without using the analytical formulations of the eigenmodes. This model can also be used in helix TWTs and coupled-cavity TWTs.
Simulation of M-type cathode performance degradation is studied based on ion bombardment with interdiffusion effect considered. Sputtered volume, sputter distribution and ion spot occurrence time can be estimated, with estimated sputtered volume close to former researches. For M-type Re-coated cathode with 300nm-thick film, ion spots were estimated to appear after 2.06×105h's working.
Beam Optics Analyzer (BOA) has the capability to design all components of an electron beam from its emitter, magnetic focusing system, to the resonant cavities and the collector. We will present the current status and advances toward the goal of making BOA a multiphysics modeling and simulation tool.
A novel three-dimensional finite-element (FE) modeling technique without matching meshes for the eigenmode analysis of arbitrary lossy slow-wave structures (SWSs) of traveling-wave tubes (TWTs) is presented. By simulating many examples, it is shown that the cold parameters of SWSs can be accurately and quickly obtained without matching meshes when using this technique. This technique would make the...
This paper presents a mode competition study for a 10kW/28GHz gyrotron. Three different codes were used for cavity simulations: a single mode self-consistent code, the multi-mode non-stationary code EURIDICE and a three-dimensional Particle-In-Cell (PIC) code based on a discontinuous Galerkin approach. Competition between first and second harmonic modes was studied.
In a helix traveling wave tube, the interaction between the electron beam and the backward wave can lead to instabilities as BWO (backward wave oscillation) if the beam current is large enough. As the efficient part of the circuit fields varies in the angular direction, a 3D tool is needed to model such a phenomena. The numerical model is presented, with some examples of BWO starting conditions research...
Modeling a gyrotron cavity in 3D and timedomain is very challenging due to the open-end features of cavity structure and higher-order mode excitation employed to achieve high efficiency. In this work, a conformal finite-difference time-domain (CFDTD) method is proposed to simulate a gyrotron cavity and a particle-in-cell (PIC) algorithm is used to describe a gyro electron beam. Our preliminary result...
The 2.5D large-signal code TESLA-FW was recently developed with the goal to model TWT amplifiers based on the serpentine or folded-waveguide slow-wave structures. Predictions of the large-signal code, applied to the modeling of the single stage amplifiers, were found in a good agreement with the results of the 3D PIC code MAGIC, while its run-time was on orders of magnitude less. To extend applicability...
A sheet-beam Extended Interaction Klystron (SBEIK) is an attractive MMW amplifier because of its high gain per unit length and compact configuration. The output cavity is an important part of the whole tube, which is used for RF power extraction. In this paper, multi-gap extended output cavity designs of SBEIK are presented by 3D simulations, RF parameters have been calculated. Beam wave interaction...
We report detailed modeling and simulations of secondary electron generation, transport, and emission from diamond cathodes. The simulations can explain the range of experimentally determined emission probability as a function of external electric field. It is essential to include conservation of transverse momentum and effective mass anisotropy when modeling emission.
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