Author: Limberg, T.
Paper Title Page
MOP060 Demonstration of SASE Suppression Through a Seeded Microbunching Instability 177
  • C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, E. Hass, K. Honkavaara, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov
    DESY, Hamburg, Germany
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school 1355.
Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.
MOP083 Start-to-End Simulation for FLASH2 HGHG Option 244
  • G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov
    DESY, Hamburg, Germany
  • K.E. Hacker
    DELTA, Dortmund, Germany
  • T. Plath
    Uni HH, Hamburg, Germany
  The Free-electron laser in Hamburg (FLASH) is the first FEL user facility to have produced extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade of FLASH named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections, a seeding undulator section and a SASE undulator section. In this paper, results from a start-to-end simulation for a FLASH2 High-Gain Harmonic Generation (HGHG) option are presented. For the beam dynamics simulation, space charge, coherent synchrotron radiation (CSR) and longitudinal cavity wake field effects are taken into account. In order to get electron beam bunches with small correlated and uncorrelated energy spread, RF parameters of the accelerating modules have been optimized as well as the parameters of the bunch compressors. Radiation simulations for the modulator and the radiator have been done with code Genesis 1.3 by using the particle distribution generated from the beam dynamics simulation. The results show that for a single stage HGHG, 33.6 nm wavelength FEL radiation can be seeded at FLASH2 with a 235 nm seeding laser.  
THP003 Two Charges in the Same Bunch Train at the European XFEL 678
  • Y.A. Kot, T. Limberg, I. Zagorodnov
    DESY, Hamburg, Germany
  The European XFEL has been initially designed for the operation with bunch charge of 1 nC (*) which was later extended down to 20 pC (**). An important upgrade of this extension might be the ability to operate different bunch charges in the same RF pulse. In this paper we assume the nominal design of the XFEL injector which means in particular that both charges in the same RF pulse experience the same solenoid field and are generated by the laser of the same rms size. We discuss the requirements which the combined working points of the injector have to fulfil and show the results of the complete start to end (S2E) and SASE simulations for the simultaneous operation of 250 pC and 500 pC bunch charges.
* DESY XFEL Project Group "The European X-Ray Free-Electron Laser. Technical Design Report" July 2007
** W. Decking and T. Limberg "European XFEL. Post-TDR Description" February 2013