Author: Li, R.K.
Paper Title Page
TUOCA02 APEX Phase-II Commissioning Results at the Lawrence Berkeley National Laboratory 1041
  • F. Sannibale, J.A. Doyle, J. Feng, D. Filippetto, G.L. Harris, M.J. Johnson, T.D. Kramasz, D. Leitner, C.E. Mitchell, J.R. Nasiatka, H.A. Padmore, H.J. Qian, H. Rasool, J.W. Staples, S.P. Virostek, R.P. Wells, M.S. Zolotorev
    LBNL, Berkeley, California, USA
  • S.M. Gierman, R.K. Li, J.F. Schmerge, T. Vecchione, F. Zhou
    SLAC, Menlo Park, California, USA
  • C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
Science needs in the last decade have been pushing the accelerator community to the development of high repetition rates (MHz/GHz-class) linac-based schemes capable of generating high brightness electron beams. Examples include X-ray FELs; ERLs for light source, electron cooling and IR to EUV FEL applications; inverse Compton scattering X-ray or gamma sources; and ultrafast electron diffraction and microscopy. The high repetition rate requirement has profound implications on the technology choice for most of the accelerator parts, and in particular for the electron gun. The successful performance of the GHz room-temperature RF photo-injectors running at rates <~ 100 Hz, cannot be scaled up to higher rates because of the excessive heat load that those regimes would impose on the gun cavity. In response to this gun need, we have developed at Berkeley the VHF-Gun, a lower-frequency room-temperature RF photo-gun capable of CW operation and optimized for the performance required by MHz-class X-ray FELs. The Advanced Photo-injector EXperiment (APEX) was funded and built for demonstrating the VHF gun performance, and the results of its last phase of commissioning are presented.
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOCA02  
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TUPMY030 Measurements of Transmitted Electron Beam Extinction through Si Crystal Membranes 1611
  • E.A. Nanni, R.K. Li, C. Limborg, X. Shen, S.P. Weathersby
    SLAC, Menlo Park, California, USA
  • W.S. Graves, R. Kirian, J. Spence, U. Weierstall
    Arizona State University, Tempe, USA
  A recently proposed method for the generation of relativistic electron beams with nanometer-scale current modulation requires diffracting relativistic electrons from a perfect crystal Si grating, accelerating the diffracted beam and imaging the crystal structure into the temporal dimension via emittance exchange. The relative intensity of the current modulation is limited by the ability to extinguish the transmitted beam via diffraction with a single-crystal Si membrane. In these preliminary experiments we will measure the extinction of the transmitted electron beam at zero scattering angle due to multiple Bragg scattering from a Si membrane with a uniform thickness of 340 nm at 2.35 MeV using the SLAC UED facility. The impact of beam divergence and charge density at the Si target will be quantified. The longevity of the Si membrane will also be investigated by monitoring the diffraction pattern as a function of time to observe the potential onset of damage to the crystal.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY030  
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