Author: Bock, M.K.
Paper Title Page
WEPA19 Report on the Redesign of the Fibre Link Stabilisation Units at FLASH 370
 
  • M.K. Bock, M. Bousonville, M. Felber, P. Gessler, T. Lamb, H. Schlarb, B. Schmidt, S. Schulz
    DESY, Hamburg, Germany
  • M. Kuntzsch
    HZDR, Dresden, Germany
  
  Funding: This work is partly supported by IRUVX-PP an EU co-funded project under FP7 (Grant Agreement 211285)
Re­cently, the fibre link sta­bil­i­sa­tion unit of the op­ti­cal syn­chro­ni­sa­tion sys­tem at FLASH has been sub­ject to sev­eral de­sign changes in­volv­ing some major is­sues. En­hance­ments of the op­ti­cal de­sign have led to im­prove­ments in the ef­fi­ciency of the free space op­tics and a new op­ti­cal delay line al­lows for a more than two times longer ad­just­ment range. The am­pli­tude noise, en­coun­tered pre­vi­ously at the re­mote sta­tion of the links, was dras­ti­cally de­creased by a new beam split­ting con­fig­u­ra­tion. In fu­ture, this new link de­sign will not only be used for the planned ad­di­tional fibre links at FLASH, but it will also re­place the al­ready in­stalled ones. In this paper we re­port on the changes of opto-me­chan­i­cal de­sign and we pre­sent first re­sults from the re­cently com­mis­sioned links. 		 
 
THPA12 Beam Energy Measurements in the FLASH Injector using Synchrotron Radiation and Bunch Arrival Monitors 489
 
  • C. Gerth, M.K. Bock, M. Hoffmann, F. Ludwig, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  
  The high beam en­ergy sta­bil­ity re­quired for sta­ble op­er­a­tion of linac-dri­ven free-elec­tron lasers de­mands for pre­cise cav­ity RF field reg­u­la­tion. This is in par­tic­u­lar true for the ac­cel­er­a­tor mod­ules at low beam en­er­gies which are used to in­duce an en­ergy cor­re­la­tion on the elec­tron beam for lon­gi­tu­di­nal bunch com­pres­sion in mag­netic chi­canes. At FLASH, a major up­grade of the in­jec­tor has taken place in the shut­down 2009/2010 in­clud­ing the in­stal­la­tion of a 3rd har­monic ac­cel­er­at­ing mod­ule, ex­change of mod­u­la­tors and re-ca­bling and tem­per­a­ture sta­bi­liza­tion of the low-level RF elec­tron­ics. Sev­eral beam-based tech­niques have been de­vel­oped re­cently which can be used to mon­i­tor the beam en­ergy with high pre­ci­sion or as fast feed­backs for the RF reg­u­la­tion. In this paper, we re­port on bunch-re­solved en­ergy mea­sure­ments recorded in­de­pen­dently with a syn­chro­tron ra­di­a­tion mon­i­tor and two bunch ar­rival mon­i­tors. Good agree­ment be­tween the mon­i­tors was found and the mea­sure­ment data are com­pared with the re­sults from RF de­tec­tion.  
 
THPA14 Upgrade of the Optical Synchronization System for FLASH II 496
 
  • M. Felber, M.K. Bock, M. Bousonville, P. Gessler, T. Lamb, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz
    DESY, Hamburg, Germany
  
  The op­ti­cal syn­chro­niza­tion sys­tem at FLASH has been in op­er­a­tion since 2008. Due to con­tin­u­ous im­prove­ment and sev­eral up­grades it has be­come an in­te­gral part of the ma­chine op­er­a­tion and of pump-probe ex­per­i­ments as both rely on its per­for­mance. In sum­mer 2013, a sec­ond FEL sec­tion, called FLASH II, which is using the same ac­cel­er­a­tor as FLASH will start its op­er­a­tion to in­crease the num­ber of user ex­per­i­ments and to test new seed­ing schemes. This also re­quires a major ex­ten­sion of the syn­chro­niza­tion sys­tem since new clients have to be sup­plied with a 10 fs-sta­ble tim­ing sig­nal. Six ad­di­tional sta­bi­lized fiber links and the ac­cord­ing end sta­tions like bunch ar­rival time mon­i­tors and laser syn­chro­niza­tion se­tups will be in­stalled.  
 
THPA26 Feedback Strategies for Bunch Arrival Time Stabilization at FLASH Towards 10 fs 531
 
  • Ch. Schmidt, M.K. Bock, W. Koprek, S. Pfeiffer, H. Schlarb
    DESY, Hamburg, Germany
  • W. Jałmużna
    TUL-DMCS, Łódź, Poland
  
  Highly pre­cise reg­u­la­tion of ac­cel­er­a­tor RF fields is a pre­req­ui­site for a sta­ble and re­pro­ducible pho­ton gen­er­a­tion at Free Elec­tron Lasers such as FLASH. Due to major im­prove­ments of the RF field con­trols dur­ing 2010 and 2011 the FEL per­for­mance and the beam sta­bil­ity was sig­nif­i­cantly im­proved. In order to fa­cil­i­tate fem­tosec­ond pre­ci­sion pump-probe and seed­ing ex­per­i­ments at FLASH a com­bi­na­tion of RF and beam based feed­back loops are used. In this paper, we pre­sent the achieved sta­bi­liza­tion of the ar­rival time and the pulse com­pres­sion at FLASH using in­tra-pulse train feed­backs. Cur­rent lim­i­ta­tions and fu­ture steps to­ward sub-10fs rms jit­ter are dis­cussed.  
 
THPA32 Femtosecond Stable Laser-to-RF Phase Detection Using Optical Modulators 551
 
  • T. Lamb, M.K. Bock, M. Bousonville, M. Felber, P. Gessler, F. Ludwig, S. Ruzin, H. Schlarb, B. Schmidt, S. Schulz
    DESY, Hamburg, Germany
  • E. Janas
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  
  Free-Elec­tron Lasers like FLASH and the Eu­ro­pean XFEL re­quire the syn­chro­niza­tion of RF sta­tions to the op­ti­cal tim­ing ref­er­ence of the ac­cel­er­a­tor. For this pur­pose, a new tech­nique to phase-lock RF sources to an op­ti­cal pulse train has been in­vented. The new tech­nique uses an opto-mi­crowave cou­pling de­vice to­gether with an ul­tra-low phase-noise RF source op­er­at­ing at a fre­quency of 1.3 GHz. In our arrange­ment, the laser-to-RF phase de­tec­tor is in­sen­si­tive to am­pli­tude fluc­tu­a­tions of the op­ti­cal ref­er­ence pulse train, which al­lows the de­tec­tor to achieve fem­tosec­ond pre­ci­sion over long time pe­ri­ods. In this paper, we pre­sent the bal­anced laser-to-RF phase de­tec­tion prin­ci­ple along with a tol­er­ance study of the arrange­ment and first re­sults from our pro­to­type setup.