A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is being developed for a microwave power module (MPM) that will be used for phased antenna array radar applications. The proposed S-band MPM...A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is being developed for a microwave power module (MPM) that will be used for phased antenna array radar applications. The proposed S-band MPM provides a tenfold peak power increase compared to state-of-the-art S-band MPMs. In this paper, the design of the vacuum power booster TWT part of the MPM is presented. The compact and lightweight S-band TWT is driven by a 6 kV, 0.9 A electron beam. The amplifier is predicted by large-signal simulations to generate over 1 kW at S-band with 25 dB saturated gain and over 40% efficiency. The stability from unwanted oscillations has been investigated. To suppress the oscillations, the helix circuit has been coated with carbon composite material. The coaxial input and output antennas have been fabricated. For efficiency enhancement, a multi-stage depressed collector (MDC) has been designed using a 3D particle-in-cell (PIC) simulator, VORPAL. The collector design makes use of a current loop based on a feedback mechanism for effective design process. The integrated designs of a helix circuit, an electron gun, a periodic permanent magnet (PPM), antennas, and a collector are presented.展开更多
The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored ...The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored are dispersive and not dissipative.The physical dispersion introduced through the source terms leads to the wide variety of plasma waves.The dispersive nature of the plasma fluid equations explored separates the work in this paper from previous publications.The linearized Euler equations with dispersive source terms are used as a model equation system to compare the wave propagation and RKDG methods.The numerical methods are then studied for applications of the full two-fluid plasma equations.The two-fluid equations describe the self-consistent evolution of electron and ion fluids in the presence of electromagnetic fields.It is found that the wave propagation method,when run at a CFL number of 1,is more accurate for equation systems that do not have disparate characteristic speeds.However,if the oscillation frequency is large compared to the frequency of information propagation,source splitting in the wave propagation method may cause phase errors.The Runge-Kutta discontinuous Galerkin method provides more accurate results for problems near steady-state as well as problems with disparate characteristic speeds when using higher spatial orders.展开更多
A discontinuous Galerkin method for the ideal 5 moment two-fluid plasma system is presented.The method uses a second or third order discontinuous Galerkin spatial discretization and a third order TVD Runge-Kutta time ...A discontinuous Galerkin method for the ideal 5 moment two-fluid plasma system is presented.The method uses a second or third order discontinuous Galerkin spatial discretization and a third order TVD Runge-Kutta time stepping scheme.The method is benchmarked against an analytic solution of a dispersive electron acoustic square pulse as well as the two-fluid electromagnetic shock[1]and existing numerical solutions to the GEM challenge magnetic reconnection problem[2].The algorithm can be generalized to arbitrary geometries and three dimensions.An approach to maintaining small gauge errors based on error propagation is suggest.展开更多
文摘A new class of compact and lightweight S-band 1 kW traveling-wave tube (TWT) is being developed for a microwave power module (MPM) that will be used for phased antenna array radar applications. The proposed S-band MPM provides a tenfold peak power increase compared to state-of-the-art S-band MPMs. In this paper, the design of the vacuum power booster TWT part of the MPM is presented. The compact and lightweight S-band TWT is driven by a 6 kV, 0.9 A electron beam. The amplifier is predicted by large-signal simulations to generate over 1 kW at S-band with 25 dB saturated gain and over 40% efficiency. The stability from unwanted oscillations has been investigated. To suppress the oscillations, the helix circuit has been coated with carbon composite material. The coaxial input and output antennas have been fabricated. For efficiency enhancement, a multi-stage depressed collector (MDC) has been designed using a 3D particle-in-cell (PIC) simulator, VORPAL. The collector design makes use of a current loop based on a feedback mechanism for effective design process. The integrated designs of a helix circuit, an electron gun, a periodic permanent magnet (PPM), antennas, and a collector are presented.
文摘The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored are dispersive and not dissipative.The physical dispersion introduced through the source terms leads to the wide variety of plasma waves.The dispersive nature of the plasma fluid equations explored separates the work in this paper from previous publications.The linearized Euler equations with dispersive source terms are used as a model equation system to compare the wave propagation and RKDG methods.The numerical methods are then studied for applications of the full two-fluid plasma equations.The two-fluid equations describe the self-consistent evolution of electron and ion fluids in the presence of electromagnetic fields.It is found that the wave propagation method,when run at a CFL number of 1,is more accurate for equation systems that do not have disparate characteristic speeds.However,if the oscillation frequency is large compared to the frequency of information propagation,source splitting in the wave propagation method may cause phase errors.The Runge-Kutta discontinuous Galerkin method provides more accurate results for problems near steady-state as well as problems with disparate characteristic speeds when using higher spatial orders.
文摘A discontinuous Galerkin method for the ideal 5 moment two-fluid plasma system is presented.The method uses a second or third order discontinuous Galerkin spatial discretization and a third order TVD Runge-Kutta time stepping scheme.The method is benchmarked against an analytic solution of a dispersive electron acoustic square pulse as well as the two-fluid electromagnetic shock[1]and existing numerical solutions to the GEM challenge magnetic reconnection problem[2].The algorithm can be generalized to arbitrary geometries and three dimensions.An approach to maintaining small gauge errors based on error propagation is suggest.
