Author: Feng, G.
Paper Title Page
MOP056 SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime 159
 
  • I.V. Agapov, G. Geloni
    XFEL. EU, Hamburg, Germany
  • G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
    DESY, Hamburg, Germany
  
  The out­put SASE char­ac­ter­is­tics of the base­line Eu­ro­pean XFEL, re­cently used in the TDRs of sci­en­tific in­stru­ments and X-ray op­tics, have been pre­vi­ously op­ti­mized as­sum­ing uni­form un­du­la­tors with­out con­sid­er­ing the po­ten­tial of un­du­la­tor ta­per­ing in the SASE regime. Here we demon­strate that the per­for­mance of Eu­ro­pean XFEL sources can be sig­nif­i­cantly im­proved with­out ad­di­tional hard­ware. The pro­ce­dure con­sists in the op­ti­miza­tion of the un­du­la­tor gap con­fig­u­ra­tion for each X-ray beam­line. Here we pro­vide a com­pre­hen­sive de­scrip­tion of the X-ray pho­ton beam prop­er­ties as a func­tion of wave­length and bunch charge. Based on nom­i­nal pa­ra­me­ters for the elec­tron beam, we demon­strate that un­du­la­tor ta­per­ing al­lows one to achieve up to a ten­fold in­crease in peak power and pho­ton spec­tral den­sity in the con­ven­tional SASE regime.  
 
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.  
 
MOP089
 Overview of FEL Seeding Activities at FLASH  
 
  • J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Mueller, T. Tanikawa
    DESY, Hamburg, Germany
  • S. Ackermann, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach
    Uni HH, Hamburg, Germany
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  
  The free-elec­tron laser fa­cil­ity FLASH at DESY op­er­ates since sev­eral years in SASE mode, de­liv­er­ing high-in­ten­sity FEL pulses in the ex­treme ultra vi­o­let and soft x-ray wave­length range for users. In order to get more con­trol of the char­ac­ter­is­tics of the FEL pulses ex­ter­nal FEL seed­ing has proven to be a re­li­able method to do so. At FLASH, an ex­per­i­men­tal setup to test sev­eral dif­fer­ent ex­ter­nal seed­ing meth­ods has been in­stalled since 2010. After suc­cess­ful demon­stra­tion of di­rect seed­ing at 38 nm, the setup is now being com­mis­sioned to op­er­ate in HGHG and EEHG mode. Fur­ther­more, other stud­ies on laser in­duced ef­fects on the elec­tron beam dy­nam­ics will be per­formed. Be­side the ex­per­i­men­tal ac­tiv­i­ties, a de­sign for the seed­ing op­tion for the FLASH2 beam­line is cur­rently under in­ves­ti­ga­tion. The goal for that is to de­velop a con­cept which is com­pat­i­ble with the op­er­a­tion of FLASH1 and which sat­is­fies the high de­mands of the fu­ture user com­mu­nity. In this con­tri­bu­tion, we give an overview of the ac­tiv­i­ties on FEL seed­ing at FLASH.