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The design work for 95 GHz, 100 kW gyrotron for Active Denial System (ADS) application is presented. The mode selection is performed considering the various technical constraints. Particle-in-Cell code is used for the beam-wave interaction computation and cavity design. In addition, the designs of electron beam source, collector and RF window are also discussed. The design results confirm the RF power...
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 microwave pulse compressor with a Magictee as an interference switch is studied. In this compressor, the necessary condition for energy storage in the compressor cavity is frequency-independent, so that the operation in different cavity eigenmodes without any mechanical tuning is possible. RF energy storage and release were simulated numerically. Output pulses in the two frequencies, 2.801 and 2...
This paper presents theory and analysis of single-tip field emission and electron beam propagation in the electrostatic focusing fields. It is shown that two gate apertures with a focusing anode allow transport of narrow electron beams over long distances without need for a confining magnetic field. Physical mechanisms of the beam formation, transport, intrinsic emittance with thermal effects, the...
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. This paper presents a source concept capable of high power in the THz range. The interaction occurs between an annular electron beam and a cylindrical grating. The grating surface-wave produces strong beam bunching and generates significant high-frequency rf. Parametric studies...
This paper presents the electrical designs of interaction cavity and electron gun for triple frequency (170-, 140-, and 127.5 GHz) gyrotron. TE34,10, TE21,11 and TE22,9 modes are selected as the operating mode for 170 GHz, 140 GHz and 127.5 GHz operation of the device, respectively. The design results show more than 1 MW power at all three frequencies.
The double corrugated waveguide was demonstrated as an effective solution for the realization of interaction structures at terahertz frequencies. By using different shapes of the corrugations, a relevant improvement of the cold parameters can be obtained. In particular lower losses are beneficial for tube performance.
A new field emitter geometry that utilizes a dielectric shield between the emitter tip and gate has been optimized to eliminate flashover in the cathode emitter cavities and improve cathode reliability. A high average power testbed has been designed and fabricated to test these cathodes at currents and current densities required for TWT operation in the X/Ku-Band frequency regime. Experimental tests...
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