Different Charges in the Same Bunch Train at the European XFEL

In this paper we have investigated the possibility of the operation of different charges in the bunch train for the nominal design of the XFEL injector and for the case that it is extended by an additional laser system on the cathode. We have examined the problem of similarity of beam optical functions for different bunch charges in a train. We report also about the sensitivity of the beam optical functions on the chosen compression scenario and give an overview over the working points for the settings at the injector for single charge operation as well as combined working points for different bunch pairs

European XFEL Post-TDR Description

This document lists and describes design changes of the European XFEL with respect to the technical design report (TDR), points out regions or components that are worked out and documented in much more detail than in the TDR, and provides an overview of possible upgrades that are presently being discussed. Includes the EDMS identifiers of detailed documents

Uncorrelated Emittance Growth in the TTF-FEL Bunch Compression Sections due to Coherent Synchrotron Radiation and Space Charge Effects

In the bunch compressing sections of the Tesla Test Facil-ity Free Electron Laser[1] (TTF FEL), short bunches travel on trajectories with small bending radii. Thus, coherent synchrotron radiation (CSR) will play a significant role in beam dynamics. The energy loss of the bunch will vary longitudinally as well as transversally across the bunch and will induce an emittance growth. The occuring transversal forces, especially the so-called “Talman force ” ([3]) and its effects on emittance have been treated before analytically for some specialized arrangements ([2, 4]). The emittance growth will affect the projective as well as the slice emittance (i.e., the emittance of sub-ensembles of particles with equal longitudinal position). The com-puter simulation code TraFiC4 calculates the fields in the bunch from first principles, thus taking into account radia-tive as well as space charge effects, which are inseparable on curved trajectories. In addition to dealing with longi-tudinal dynamics [5], this code has now been extended to handle the transversal dynamics of the bunch. We use it to study the behavior of the fields across the beam and the re-sulting slice and projective emittance growth. We study its dependence on bunch parameters such as charge and shape and investigate possible cures by shielding.

Beam-based Alignment in the European XFEL SASE1

The European X-ray Free Electron Laser (E-XFEL) provides an ultra-short and high-brilliant photon pulses of spatially coherent X-rays with wavelengths down to 0.5 A by using three undulator systems. Within these undulator systems, the orbit trajectory is required to be straight to a few micron over each gain length, so that the photon beam is capable of overlapping efficiently with the electron beam. However,this requirement is not obtainable with ordinary mechanical alignment methods. For this reason, a beam-based alignment (BBA) method using BPM readings of different beam energies is applied to the E-XFEL SASE1 undulators. In this report, we describe the BBA simulation for SASE1 including alignment errors of quadrupoles and BPMs. After correction, the desired range of the orbit trajectory is attained with high condence. In addition, to identify the reliability of an aligned orbit trajectory acquired from the BBA simulation, we present here the SASE FEL radiation simulation, in which we observe a slight decrease of radiation energy and power