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