Author: Yurkov, M.V.
Paper Title Page
MOP055 Start-to-End Simulations for IR/THz Undulator Radiation at PITZ 153
 
  • P. Boonpornprasert, M. Khojoyan, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • B. Marchetti, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • S. Rimjaem
    Chiang Mai University, Chiang Mai, Thailand
  
  High bright­ness elec­tron sources for mod­ern linac-based Free-Elec­tron Lasers (FELs) have been char­ac­ter­ized and op­ti­mized at the Photo In­jec­tor Test fa­cil­ity at DESY, Zeuthen site (PITZ). Since the time struc­ture of the elec­tron bunches at PITZ is iden­ti­cal to those at the Eu­ro­pean XFEL, the PITZ ac­cel­er­a­tor is being con­sid­ered as a proper ma­chine for the de­vel­op­ment of an IR/THz source pro­to­type for pump and probe ex­per­i­ments planned at the Eu­ro­pean XFEL. Tun­able IR/THz ra­di­a­tion sources using syn­chro­tron ra­di­a­tion from a di­pole mag­net, tran­si­tion ra­di­a­tion, high gain FELs and co­her­ent ra­di­a­tion of tai­lored or pre­mod­u­lated beams are cur­rently under con­sid­er­a­tion. This work de­scribes start-to-end sim­u­la­tions for gen­er­at­ing the FEL ra­di­a­tion using an AP­PLE-II un­du­la­tor with elec­tron beams pro­duced by the PITZ ac­cel­er­a­tor. Analy­sis of the phys­i­cal pa­ra­me­ter space has been per­formed with tools of the FAST pro­gram code pack­age. Elec­tron Beam dy­nam­ics sim­u­la­tions were per­formed by using the ASTRA code, while the GEN­E­SIS 1.3 code was used to study the SASE process. The re­sults of these stud­ies are pre­sented and dis­cussed in this paper.  
 
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. 		 
 
MOP064 Statistical Properties of the Radiation from SASE FEL Operating in a Post-saturation Regime with and without Undulator Tapering 194
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  We de­scribe sta­tis­ti­cal and co­her­ence prop­er­ties of the ra­di­a­tion from x-ray free elec­tron lasers (XFEL) op­er­at­ing in the post-sat­u­ra­tion regime. We con­sider prac­ti­cal case of the SASE3 FEL at Eu­ro­pean XFEL. We per­form com­par­i­son of the main char­ac­ter­is­tics of X-ray FEL op­er­at­ing in the post-sat­u­ra­tion regime with and with­out un­du­la­tor ta­per­ing: ef­fi­ciency, co­her­ence time and de­gree of trans­verse co­her­ence.  
 
MOP065 Optimization of a High Efficiency FEL Amplifier 199
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  The prob­lem of an ef­fi­ciency in­crease of an FEL am­pli­fier is now of great prac­ti­cal im­por­tance. Tech­nique of un­du­la­tor ta­per­ing in the post-sat­u­ra­tion regime is used at the ex­ist­ing x-ray FELs LCLS and SACLA, and is planned for use at the Eu­ro­pean XFEL, Swiss FEL, and PAL XFEL. There are also dis­cus­sions on the fu­ture of high peak and av­er­age power FELs for sci­en­tific and in­dus­trial ap­pli­ca­tions. In this paper we per­form de­tailed analy­sis of the ta­per­ing strate­gies for high power seeded FEL am­pli­fiers. Ap­pli­ca­tion of sim­i­lar­ity tech­niques al­lows us to de­rive uni­ver­sal law of the un­du­la­tor ta­per­ing.  
 
MOP066 An Overview of the Radiation Properties of the European XFEL 204
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  We pre­sent an overview of the ra­di­a­tion prop­er­ties of the Eu­ro­pean XFEL based on re­cently ac­cepted strat­egy of op­er­a­tion at the fixed set of elec­tron en­er­gies (8.5 GeV, 12 GeV, 14 GeV, and 17.5 GeV), base­line pa­ra­me­ters if the elec­tron beam, and new set un­du­la­tor pa­ra­me­ters. We also dis­cuss po­ten­tial ex­ten­sion of the pa­ra­me­ter space which does not re­quire new hard­ware and can be re­al­ized at a very early stage of the Eu­ro­pean XFEL op­er­a­tion.  
 
MOP067 Prospects for CW Operation of the European XFEL in Hard X-ray Regime 210
 
  • R. Brinkmann, E. Schneidmiller, J.K. Sekutowicz, M.V. Yurkov
    DESY, Hamburg, Germany
  
  The Eu­ro­pean XFEL will op­er­ate nom­i­nally at 17.5 GeV in SP (short pulse) mode with 0.65 ms long bunch train and 10 Hz rep­e­ti­tion rate. A pos­si­ble up­grade of the linac to CW (con­tin­u­ous wave) or LP (long pulse) modes with a cor­re­spond­ing re­duc­tion of elec­tron beam en­ergy is under dis­cus­sion since many years. Re­cent suc­cesses in the ded­i­cated R&D pro­gram allow to fore­cast a tech­ni­cal fea­si­bil­ity of such an up­grade in the fore­see­able fu­ture. One of the chal­lenges is to pro­vide sub-Angstroem FEL op­er­a­tion in CW and LP modes. In this paper we per­form a pre­lim­i­nary analy­sis of a pos­si­ble op­er­a­tion of the Eu­ro­pean XFEL in the hard X-ray regime in CW and LP modes with the en­er­gies of 7 GeV and 10 GeV, re­spec­tively. We con­sider las­ing in the base­line XFEL un­du­la­tor as well as in a new un­du­la­tor with a re­duced pe­riod. We show that, with rea­son­able re­quire­ments on elec­tron beam qual­ity, las­ing on the fun­da­men­tal will be pos­si­ble in sub-Angstroem regime. As an op­tion for gen­er­a­tion of bril­liant pho­ton beams at short wave­lengths we also con­sider har­monic las­ing that has re­cently at­tracted a sig­nif­i­cant at­ten­tion.  
 
MOP068 Suppression of the Fundamental Frequency for a Successful Harmonic Lasing in SASE FELs 215
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Har­monic las­ing in X-ray FELs has re­cently at­tracted a sig­nif­i­cant at­ten­tion and is now se­ri­ously con­sid­ered as a po­ten­tial method for gen­er­a­tion of bril­liant pho­ton beams at short wave­lengths. It is clear, how­ever, that for a suc­cess­ful har­monic las­ing one has to sup­press the fun­da­men­tal. In this paper we dis­cuss dif­fer­ent meth­ods for such a sup­pres­sion: phase shifters, in­traun­du­la­tor spec­tral fil­ter­ing, switch­ing be­tween the 3rd and the 5th har­mon­ics etc.  
 
MOC01 Circular Polarization Control by Reverse Undulator Tapering 297
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  In order to pro­duce cir­cu­larly po­lar­ized light at X-ray FEL fa­cil­i­ties one can con­sider an in­stal­la­tion of a short he­li­cal (or cross-pla­nar) af­ter­burner, but then one should have an ef­fi­cient method to sup­press pow­er­ful lin­early po­lar­ized back­ground from the main un­du­la­tor. We pro­pose a new method for such a sup­pres­sion: an ap­pli­ca­tion of the re­verse taper in the main un­du­la­tor. We dis­cover that in a cer­tain range of the taper strength, the den­sity mod­u­la­tion (bunch­ing) at sat­u­ra­tion is prac­ti­cally the same as in the case of non-ta­pered un­du­la­tor while the power of lin­early po­lar­ized ra­di­a­tion is sup­pressed by or­ders of mag­ni­tude. Then strongly mod­u­lated elec­tron beam ra­di­ates at full power in the af­ter­burner. Con­sid­er­ing SASE3 un­du­la­tor of the Eu­ro­pean XFEL as a prac­ti­cal ex­am­ple, we demon­strate that soft X-ray ra­di­a­tion pulses with peak power in ex­cess of 100 GW and an ul­ti­mately high de­gree of cir­cu­lar po­lar­iza­tion can be pro­duced. The method can be used at dif­fer­ent X-ray FEL fa­cil­i­ties, in par­tic­u­lar at LCLS after in­stal­la­tion of the he­li­cal af­ter­burner in the near fu­ture.  
slides icon Slides MOC01 [1.545 MB]  
 
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]  
 
TUP031 FEL Code Comparison for the Production of Harmonics via Harmonic Lasing 451
 
  • G. Marcus, W.M. Fawley
    SLAC, Menlo Park, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Har­monic las­ing of­fers an at­trac­tive op­tion to sig­nif­i­cantly ex­tend the pho­ton en­ergy range of FEL beam­lines. Here, the fun­da­men­tal FEL ra­di­a­tion is sup­pressed by var­i­ous com­bi­na­tions of phase shifters, at­ten­u­a­tors, and de­tuned un­du­la­tors while the ra­di­a­tion at a de­sired har­monic is al­lowed to grow lin­early. The sup­port of nu­mer­i­cal sim­u­la­tions is ex­ten­sively used in eval­u­at­ing the per­for­mance of this scheme. This paper com­pares the re­sults of har­monic growth in the har­monic las­ing scheme using three FEL codes: FAST, GEN­E­SIS, and GIN­GER.  
 
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