Author: Stojanovic, N.
Paper Title Page
MOP006
 Coherent Accelerator-based High Field THz Radiation at FLASH II  
 
  • T. Golz, V. B. Asgekar, B. Faatz, G. Geloni, N. Stojanovic, M. Tischer, P. Vagin, M. Vogt
    DESY, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • P. Vobly
    BINP SB RAS, Novosibirsk, Russia
  
  Funding: BMBF grant no. 05K10CHC + 05K10KEB + 05K12CH4
Lin­ear ac­cel­er­a­tor based light sources with their tun­able broad spec­tral range (THz to hard X-rays regime) and their abil­ity to gen­er­ate ul­tra-short pulses with peak in­ten­si­ties many or­ders of mag­ni­tude higher then syn­chro­tron sources, gave rise to a new field of ul­tra­fast physics. In the THz range, the abil­ity of 4th gen. light sources to gen­er­ate pulses with e-field strengths up to 1 GV/m opened the door to the field of non-lin­ear THz spec­troscopy and THz-con­trolled ma­te­r­ial sci­ence. The main ad­van­tage of ac­cel­er­a­tor-based THz is its scaleabil­ity. As the process is not bound to a par­tic­u­lar medium, but oc­curs in the ac­cel­er­a­tor vac­uum, it by­passes the lim­i­ta­tion of table top sources. In ad­di­tion, it has been demon­strated that co­her­ent THz ra­di­a­tion can be gen­er­ated along fem­tosec­ond X-ray pulses in 4th Gen­er­a­tion X-ray Light sources such as FLASH [1,2,3] and LCLS [4]. This opens up the op­por­tu­nity for nat­u­rally syn­chro­nized THz pump X-ray probe ex­per­i­ments on a few fem­tosec­ond time scale [1,2,4]. Here we pre­sent the de­sign for the THz source at FLASH2, which takes new find­ings [5] and chal­lenges into ac­count that we face dur­ing the ra­di­a­tion trans­port to the ex­per­i­men­tal hall. 		 
 
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. 		 
 
TUB04 Operation of FLASH with Short SASE-FEL Radiation Pulses 342
 
  • J. Rönsch-Schulenburg, E. Hass, N.M. Lockmann, T. Plath, M. Rehders, J. Roßbach
    Uni HH, Hamburg, Germany
  • G. Brenner, S. Dziarzhytski, T. Golz, H. Schlarb, B. Schmidt, E. Schneidmiller, S. Schreiber, B. Steffen, N. Stojanovic, S. Wunderlich, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper de­scribes the ex­per­i­men­tal ac­tiv­ity on the gen­er­a­tion of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-elec­tron laser FLASH [1, 2]. The key el­e­ment, a photo-in­jec­tor laser which is able to gen­er­ate laser pulses of about 2 ps FWHM has been op­ti­mized and com­mis­sioned. It al­lows the gen­er­a­tion of shorter bunches with low bunch charge (of up to 200 pC) di­rectly at the photo-cath­ode. Ini­tially shorter in­jec­tor laser pulses and thus shorter bunches eases the re­quired bunch com­pres­sion fac­tor for short pulses below 10 fs du­ra­tion which makes op­er­a­tion of the elec­tron beam for­ma­tion sys­tem to be more ro­bust with re­spect to jit­ters and col­lec­tive ef­fects. As a re­sult, over­all sta­bil­ity of SASE FEL per­for­mance is im­proved. In the op­ti­mal case sin­gle-spike op­er­a­tion can be achieved. In this paper the ex­per­i­men­tal re­sults on pro­duc­tion of short elec­tron bunches and the SASE per­for­mance using the new in­jec­tor laser will be shown and the mea­sured elec­tron bunch and FEL ra­di­a­tion prop­er­ties are dis­cussed. In ad­di­tion, op­ti­miza­tions of bunch di­ag­nos­tics for low charge and short bunches are dis­cussed. 		 
slides icon Slides TUB04 [1.201 MB]  
 
THA04
 Optical Afterburner for Naturaly Synchronized Pump-probe Experiments at FLASH  
 
  • N. Stojanovic, A. Al-Shemmary, D. Espeloer, T. Golz, R. Riedel, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • M. Foerst
    CFEL, Hamburg, Germany
  • M. Gensch
    HZDR, Dresden, Germany
  • F. Tavella
    HIJ, Jena, Germany
  
  Funding: German Federal Ministry for Education and Research, project 05K10CHC and 05K12CH4
We em­ploy so- called Op­ti­cal Af­ter­burner [*,**] prin­ci­ple to gen­er­ate op­ti­cal replica pulses of X-ray pulse at FLASH (Free Elec­tron LASer in Ham­burg). These pulses are nat­u­rally syn­chro­nized to the FEL pulses and share the same en­ve­lope and ar­rival time, with ac­cu­racy down to few fem­tosec­onds. Be­cause of this, Op­ti­cal Af­ter­burner pulses can be used for com­plete tem­po­ral di­ag­nos­tics for FEL pulses. Be­cause we shift di­ag­nos­tics chal­lenge from X-ray to vis­i­ble range, this sig­nif­i­cantly sim­pli­fies de­tec­tion. Dur­ing pulse- du­ra­tion mea­sure­ment cam­paigns at FLASH, Op­ti­cal Af­ter­burner has been demon­strated as ver­sa­tile and ac­cu­rate tool to mea­sure pulse du­ra­tion of X-ray FEL pulses. In the most re­cent de­vel­op­ment we have am­pli­fied, Op­ti­cal Af­ter­burner pulses by three or­ders of mag­ni­tude and will used it in the X-ray/Vis­i­ble pump-probe ex­per­i­ments for ul­ti­mate tem­po­ral res­o­lu­tion. We have demon­strated am­pli­fi­ca­tion con­cept at FLASH, where we reach pulse en­er­gies above 1uJ at 1MHz rep­e­ti­tion rate.
References:
* E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 030701 (2010)
* Proceedings of IPAC2011, San Sebastián, Spain. THPC084
 		 
 
THP065
 Towards a Novel THz-based Monitor for Subpicosecond Electron Bunches Working at MHz Repetition Rates and Low Bunch Charges  
 
  • B.W. Green, M. Gensch, S. Kovalev
    HZDR, Dresden, Germany
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • T. Golz, N. Stojanovic
    DESY, Hamburg, Germany
  • M. Kuntzsch
    TU Dresden, Dresden, Germany
  
  The con­trol and mea­sure­ment of elec­tron bunch prop­er­ties at the fem­tosec­ond (fs) level has be­come an im­por­tant field in mod­ern ac­cel­er­a­tor physics, in par­tic­u­lar since these be­came cru­cial pa­ra­me­ters for the op­er­a­tion of 4th Gen­er­a­tion X-ray Light-sources. In order to op­er­ate mod­ern-day pho­ton fac­to­ries such as LCLS and the fu­ture Eu­ro­pean X-FEL re­li­ably, a num­ber of novel ap­proaches have been de­vel­oped that allow the non­in­va­sive mea­sure­ment of elec­tron bunch form and ar­rival time. Some of those are based on the elec­tro-op­tic de­tec­tion of the coulomb field of the elec­tron bunches in the elec­tron beam­line; some de­tect the su­per-ra­di­ant THz pulses from the elec­tron bunch. How­ever, none of these con­cepts al­lows for pulse-to-pulse de­tec­tion on a quasi-CW ac­cel­er­a­tor op­er­at­ing at the MHz rep­e­ti­tion rates planned for the next gen­er­a­tion of X-ray free elec­tron lasers. In this con­tri­bu­tion we pre­sent first re­sults from a new mon­i­tor con­cept, based on the sin­gle-shot elec­tro-op­tic de­tec­tion of su­per-ra­di­ant THz pulses, that has the po­ten­tial to op­er­ate at MHz rep­e­ti­tion rates.  
poster icon Poster THP065 [1.966 MB]