47 research outputs found

    Harmonic operation of a free-electron laser

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    Harmonic operation of a free-electron-laser amplifier is studied. The key issue investigated here is suppression of the fundamental. For a tapered amplifier with the right choice of parameters, it is found that the presence of the harmonic mode greatly reduces the growth rate of the fundamental. A limit on the reflection coefficient of the fundamental mode that will ensure stable operation is derived. The relative merits of tripling the frequency by operating at the third harmonic versus decreasing the wiggler period by a factor of 3 are discussed

    Experimental demonstration of a W-band gyroklystron amplifier

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    The experimental demonstration of a four cavity W-band (93 GHz) gyroklystron amplifier is reported. The gyroklystron has produced 67 kW peak output power and 28% efficiency in the TE011 mode using a 55 kV, 4.3 A electron beam. The full width at half maximum instantaneous bandwidth is greater than 460 MHz, a significant increase over the bandwidth demonstrated in previous W-band gyroklystron amplifier experiments. The amplifier is unconditionally stable at this operating point. Experimental results are in good agreement with theoretical predictions

    An Advanced Electromagnetic Eigenmode Solver for Vacuum Electronics Devices -CTLSS ࣿ

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    Abstract The Cold-Test and Large-Signal Simulation code (CTLSS), a design tool for vacuum electronics devices, is presented. The prototype tool is a three-dimensional, frequencydomain cold-test code that operates on a rectangular structured grid. It uses a generalisation [1] of the JacobiDavidson algorithm [2] that has proven effective in solving for eigenmodes in problems having sharp-edged structures with materials having large dielectric constants and loss tangents as high as 100%. We present the CTLSS algorithm and code features that are useful for vacuum electronics design. Analysis of both closed cavities and periodic slow-wave structures are given. Tests indicate that the CTLSS algorithm can determine mode frequencies to well below 0.1% accuracy for all modes computed. A new formulation has been implemented to compute the complex axial wavenumber, k z , in a periodic waveguide, as the eigenvalue for a specified real frequency, and test results will be presented. This code is being extended to include an unstructured mesh for the conformal representation of structures using high order element

    CIRCUIT ASPECTS OF THE NRL/INDUSTRIAL 94 GHz GYROKLYSTRON AMPLIFIER

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    Abstract A wide bandwidth, high average power W-band gyroklystron amplifier is currently under cooperative development by NRL, Litton Electron Devices, and Communication and Power Industries. The amplifier circuit is comprised of 4 stagger-tuned cavities operating in the fundamental TE 011 circular cavity mode. The input coupler is the first cavity of the circuit and must exhibit reasonable coupling strength between the TE 10 mode in rectangular waveguide and the desired TE 011 circular cavity mode over a better than 600 MHz bandwidth centered at 93.4 GHz, with high TE 01 mode purity. A single WR-8 rectangular waveguide drives a combined coaxial/cylindrical cavity system. The coaxial cavity resonating in the TE 411 mode is tightly coupled to the cylindrical cavity, excited to resonate in the TE 011 mode. The rf magnetic field couples the cavities through 4 azimuthally spaced apertures

    Viability of the 11

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    Simulation of noise-power ratio with the large-signal code CHRISTINE

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