%\cite{Decker:FEL2015-WEP023} \bibitem{Decker:FEL2015-WEP023} F.-J.~Decker, S.~Gilevich, Z.~Huang, H.~Loos, A.~Marinelli, C.A.~Stan, \emph{et al.}, % F.-J. Decker \emph{et al.}, \textquotedblleft{Two Bunches with ns-Separation with LCLS}\textquotedblright, % in \emph{Proc. FEL2015}, WEP023, pp. 634--638, % in \emph{Proc. FEL2015}, Daejeon, Republic of Korea, August 2015, paper WEP023, pp. 634--638, in \emph{Proc. 37th International Free Electron Laser Conference (FEL2015)}, Daejeon, Republic of Korea, August 2015, paper WEP023, pp. 634--638, ISBN: 978-3-95450-134-2, \url{http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/wep023.pdf}, doi:10.18429/JACoW-FEL2015-WEP023, 2015.