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During the last few years, we have successfully gained a qualitative understanding of the basic physics of breakdown phenomena in high vacuum RF structures. We have been able to use this knowledge of geometrical effects and material properties to develop accelerator structures with gradients well above the state of the art. It has now been demonstrated that room temperature linacs can operate at gradients...
The development of high-frequency vacuum electronics structures is hampered by the enormous technological challenges of high-precision three-dimensional machining required for shorter wavelengths. I will describe the possibilities of employing electromagnetic metamaterials (MTMs) to address some of these challenges. In this talk I will first review some of the recent progress in metamaterials-inspired...
In 2008, Dr. Mark Rosker presented a Plenary presentation describing his vision of issues and requirements above 100 GHz which would drive vacuum electronic device research and development. Since that time, the author has joined DARPA and has instituted programs that are dependent upon those device development programs discussed. This presentation will revisit those issues and requirements, discuss...
Dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) spectroscopy has emerged as a new and growing application for high-frequency, continuous wave (cw) vacuum electronic devices capable of producing powers in the range of tens to hundreds of watts at millimeter-wave and terahertz frequencies. As an original equipment manufacturer of gyrotrons for Bruker Biospin DNP spectrometers,...
We present new capabilities introduced in the 3D Electromagnetic Particle-in-Cell code Neptune to directly support rapid simulation-based design of a broad range of vacuum electronic devices.
Toward the goal of making Beam Optics Analyzer (BOA) a multiphysics modeling and simulation tool for electron beam devices, we will present the new nonlinear heat transfer capability in BOA. We will discuss the finite element formulation and numerical results with regard to temperature dependent materials and radiative heat transfer coupled with power densities generated from electron beams.
We report on the extension and further generalization of two different large-signal models suitable for the 2D modeling of TWTs based on different types of slow-wave structures. The initial implementation of the 2D large-signal codes TESLA-CC and TESLA-FW has been generalized in such way to create a single algorithm with modular extensions that can be applied to the modeling of coupled-cavity or serpentine/folded-waveguide...
An analysis of the propagation characteristics of coupled-cavity (CC) delay lines in traveling-wave tubes (TWTs) under hot conditions is proposed. Using this approach a necessary impedance level at the end of the periodic line is derived that leads to minimum input reflections during operation. From this matching condition a required cold input reflection can be predicted which is in general different...
COLLGUN, designed to simulate multistage depressed collectors, was optimized by using parallel computing. This work reports the speedups observed on a parallel implementation of the COLLGUN code using CUDA. Were parallelized the solver of the sparse system for the electric scalar potential using the Incomplete Cholesky Conjugate Gradient Method (a) and the determination of the electric field inside...
NRL's unique sheet-beam electron gun, which produces a 3.5-4-A, 0.3×4 mm electron beam at ∼20 kV, has been successfully used to power multi-kW amplifiers at both Ka and W bands. The 94-GHz narrow-band EIK uses a 3-cavity circuit to produce a peak output power of over 7.5 kW, with saturated gain of ∼35 dB. The Ka-band amplifier uses a double staggered ladder coupled-cavity circuit to achieve a peak...
In this paper, the development of X-band and W-band sheet beam klystron (SBK) is introduced thoroughly in IECAS recently. The compact planar PCM and closed PCM system are used to focus the sheet beam for both of two types SBK. For the five multi-gap-cavity X-band SBK (XSBK), the cross section of beam is of 50mmx4mm, and with the beam voltage of 150kV, beam current of 100A, the designed output power...
Development of a 200 kW CW sheet beam klystron for the Office of Naval Research. Specifications, beam stability, and cathode bell jar testing are discussed.
The suppression of TE mode oscillations in a PPM-focused S-band sheet beam klystron amplifier using a method of loading distributed losses is presented. This method allows us to make a reasonable attenuation of unwanted modes relative to the operating TM mode and can be used to improve the stability of beam-wave interaction circuit with high aspect ratio.
A gyrotron operating in the TE20, 9 interaction mode at 117.5 GHz has been developed. Communications and Power Industries (CPI) has designed, fabricated, and conducted initial testing of this device. Short pulse testing demonstrates output power levels up to 1.8 MW, with electrical efficiencies of up to 42% (including the effect of a single-stage depressed collector), for an accelerating voltage of...
Physical design studies towards DEMO-compatible gyrotrons (frequency above 230 GHz, output power above 1 MW, frequency-tunable) have been started at KIT. Usage of very high-order modes (eigenvalue above 120) is necessary and allows a novel mode-selection strategy. Two different resonator designs for 237.5 GHz gyrotrons are under investigation.
The microwave vacuum electronics is regarded to make sense only if producing sufficiently high powers at sufficiently high frequencies. And if intense microwave flows are produced, they may be transmitted only with oversized waveguides or mirror lines, such configurations being equipped with relevant miltiplexers, filters, duplexers and other components of quasi-optical types.
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