TY - CPAPER
AU - Schneidmiller, E.
AU - Yurkov, M.V.
TI - Fundamental Limitations of the SASE FEL Photon Beam Pointing Stability
J2 - Proc. of FEL2015
AB - The radiation from SASE FEL has always limited value of the degree of transverse coherence. Two effects define the spatial coherence of the radiation: the mode competition effect, and the effect of poor longitudinal coherence. For the diffraction limited case we deal mainly with the effect of the poor longitudinal coherence leading to significant degradation of the spatial coherence in the post-saturation regime. When transverse size of the electron beam significantly exceeds diffraction limit, the mode competition effect does not provide the selection of the fundamental FEL mode, and spatial coherence degrades due to contribution of the higher azimuthal modes. Another consequence of this effect are fluctuations of the spot size and pointing stability of the photon beam. These fluctuations are fundamental and originate from the shot noise in the electron beam. The effect of pointing instability becomes more pronouncing for shorter wavelengths. Our study is devoted to the fundamental analysis of the effect and description of possible means for improving the degree of transverse coherence and the pointing stability.
PB - JACoW
CY - Geneva, Switzerland
SP - 397
EP - 404
KW - FEL
KW - radiation
KW - emittance
KW - electron
KW - undulator
DA - 2015/12
PY - 2015
SN - 978-3-95450-134-2
DO - 10.18429/JACoW-FEL2015-TUP021
UR - http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/tup021.pdf
ER -