Author: Franzi, M.A.
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MOOCA01 R&D of a Super-compact SLED System at SLAC 39
  • J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu
    SLAC, Menlo Park, California, USA
  Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
slides icon Slides MOOCA01 [20.278 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01  
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MOPMW038 Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators 487
  • A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda
    SLAC, Menlo Park, California, USA
  • J. Guo
    JLab, Newport News, Virginia, USA
  • Y. Higashi
    OIST, Onna-son, Okinawa, Japan
  Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW038  
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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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