Author: Jensen, A.
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MOPMW042 Multi-Dimensional RF Sources Design 501
  • M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
Vacuum electronic devices, such as rf sources for accelerator applications, must provide high rf power with high efficiency. To achieve these requirements, multi-beam klystron and sheet-beam klystron devices have been developed. Multi-beam klystrons, at high frequency employ separate output cavities; hence they have the disadvantage that combining all the rf pulses, generated by all the beams, is challenging. Sheet-beam klystrons have problems with instabilities and with space charge forces that makes the beam not naturally confined. We are proposing an alternative approach that reduces space charge problems, by adopting geometries in which the space charge forces are naturally balanced. An example is when the electron beam is generated by a central source (well) and the electron motion corresponds to the natural expansion of the electron cloud (three-dimensional device). In this paper we will present the design and challenges of a bi-dimensional rf source, a cylindrical klystron, composed by concentric pancake resonant cavities. In this case, space charge forces are naturally balanced in the azimuthal direction.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW042  
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MOPMY034 The Distributed Bunch Amplifier 573
  • M.A. Franzi, A. Jensen, S.G. Tantawi, F. Toufexis, A.R. Vrielink
    SLAC, Menlo Park, California, USA
  The Distributed Bunch Amplifier (DBA) is a high efficiency RF source that utilizes a phase locked deflecting cavity and output circuit to produce a synchronous beam-wave interaction. The DBA improves on the design of previous embodiments of this technology, such as the Gyrocon*, by implementing a modern decoupled output circuit design and conical PPM beam focusing array in order to scale to higher frequencies and efficiency than previously demonstrated. Presented is a proof-of-concept S-band, 2.856 GHz, device operating with a 60 kV, 8 Amp, electron beam. Each stage of the three-cavity decoupled output circuit is optimized based on complex amplitude and shunt impedance to achieve an electronic efficiency of greater than 90%. Initial numerical analysis of this design indicates that an overall operating efficiency of greater than 70% is feasible. Detailed simulated results of the S-band model and designs to scale this technology to higher power and frequency will be discussed.
* Budker, G. I., et al. "The Gyrocon: An Efficient Relativistic High Power VHF Generator." Part. Accel. 10 (1979): 41-59.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY034  
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MOPMY036 High-harmonic mm-Wave Frequency Multiplication using a Gyrocon-like Device 579
  • F. Toufexis, V.A. Dolgashev, M.V. Fazio, A. Jensen, S.G. Tantawi, A.R. Vrielink
    SLAC, Menlo Park, California, USA
  • P. Borchard
    Dymenso LLC, San Francisco, USA
  Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation.
Traditional linear interaction RF sources, such as Klystrons and Traveling Wave Tubes, fail to produce significant power levels at millimeter wavelengths. This is because their critical dimensions are small compared to the wavelength, and the output power scales as the square of the wavelength. We present a vacuum tube technology, where the device size is inherently larger than the operating wavelength. We designed a low–voltage mm–wave source, with an output interaction circuit based on a spherical sector cavity. This device was configured as a phased-locked frequency multiplier. We report the design and cold test results of a proof-of-principle fifth harmonic frequency multiplier with an output frequency of 57.12 GHz.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY036  
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