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Stupakov, G. V.

Paper Title Page
TUPPH030 Longitudinal and Transverse Self-forces in Relativistic Line-charge Beam 309
 
  • G. V. Stupakov
    SLAC, Menlo Park, California
  
  An attempt to compute self-fields of a beam with negligible transverse dimensions (line-charge beam) leads to logarithmically diverging result. On the other hand, the well known expression* for the steady state coherent synchrotron radiation (CSR) wake does not involve the transverse beam size and is applicable to beams with infinitely thin transverse dimensions. In this work, we formulate the general problem of calculation of longitudinal and transverse forces in a relativistic beam in such a way that, in its essential part, does not involve the transverse dimensions of the bunch, and can be computed using a line-charge model for the beam. Our approach covers the case of short magnets and beams with energy chirp. We also show that there is a potential part of the longitudinal force (neglected in most previous considerations) that is responsible for the so called compression work. Our approach can be useful for quick calculation of the CSR effects in bunch compressors.

* Ya. S. Derbenev et al. "Microbunch Radiative Tail-Head Interaction", DESY FEL Report TESLA-FEL 95-05, 1995; J. Murphy et al. Part. Accel., vol. 57, 9 (1997).

 
TUPPH027 Measurements of Coherent Synchrotron Radiation and its Impact on the LCLS Electron Beam 298
 
  • Z. Huang, K. L.F. Bane, F.-J. Decker, Y. T. Ding, D. Dowell, P. Emma, J. C. Frisch, R. H. Iverson, C. Limborg-Deprey, H. Loos, H.-D. Nuhn, G. V. Stupakov, J. L. Turner, J. J. Welch, J. Wu
    SLAC, Menlo Park, California
  • D. F. Ratner
    Stanford University, Stanford, Califormia
  
  The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. Two separate magnetic dipole chicanes are used in the SLAC linac to compress the electron bunch length in stages, in order to reach the high peak current required for an x-ray FEL. In the bunch compressors, coherent synchrotron radiation (CSR) can be emitted–induced either by a short electron bunch, or by any longitudinal density modulation that may be on the bunch. We present measurements, simulations, and analysis of
  1. the CSR-induced energy loss,
  2. the related transverse emittance growth, and
  3. the microbunching-induced CSR directly observed at optical wavelengths.