Short Wavelength FELs
Paper Title Page
WEPSO01 Free Electron Lasers in 2013 486
 
  • J. Blau, K. R. Cohn, W.B. Colson, R. Vigil
    NPS, Monterey, California, USA
 
  Funding: This work has been supported by the Office of Naval Research.
Thirty-seven years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and discussed.
 
 
WEPSO05 Progress of the LUNEX5 Project 502
 
  • M.-E. Couprie, C. Benabderrahmane, L. Cassinari, J. Daillant, C. Evain, N. Hubert, M. Labat, A. Loulergue, J. Lüning, P. Marchand, O. Marcouillé, C. Miron, P. Morin, A. Nadji, P. Roy, T. Tanikawa
    SOLEIL, Gif-sur-Yvette, France
  • S. Bielawski, M. Le Parquier, E. Roussel, C. Szwaj
    PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
  • B. Carré, D. Garzella
    CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
  • N. Delerue
    LAL, Orsay, France
  • G. Devanz
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Dubois
    CCPMR, Paris, France
  • G. Lambert, R. Lehé, V. Malka, C. Thaury
    LOA, Palaiseau, France
  • G. Le Bec
    ESRF, Grenoble, France
  • M. Luong
    CEA/DSM/IRFU, France
 
  LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region, with a 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), feeding a single Free Electron Laser line with seeding with High order Harmonic in Gas and Echo Enable Harmonic Generation. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies from a LWFA with more realistic beam parameters (1 % energy spread, 1 μm size and 1 mrad divergence) than the ones taken in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. The French scientific community is increasing its participation to the use of operating FELs.  
 
WEPSO07 Simulation Studies for an X-ray FEL Based on an Extension of the MAX IV Linac 510
 
  • F. Curbis, N. Čutić, O. Karlberg, F. Lindau, A.W.L. Mak, E. Mansten, S. Thorin, S. Werin
    MAX-lab, Lund, Sweden
 
  It is well known that the few X-ray FELs around the world are severely overbooked by users. Having a medium energy linac, such as the one now being installed at the MAX IV laboratory, it becomes natural to think about slightly increasing the electron energy to drive an X-ray FEL. This development is now included in the long term strategic plan for the MAX IV laboratory. We will present the current FEL studies based on an extension of the MAX IV linac to 5 GeV to reach the Angstrom region. The injector for the MAX IV accelerator complex is also equipped with a photocathode gun, capable of producing low emittance electron beam. The bunch compression and linearization of the beam is taken care by two double achromats. The basic FEL layout would consist of short period undulators with tapering for extracting all the power from the electron beam. Self-seeding is considered as an option for increasing the spectral and intensity stability.  
 
WEPSO24 Compact XFEL Light Source 757
 
  • W.S. Graves, K.K. Berggren, F.X. Kaertner, D.E. Moncton
    MIT, Cambridge, Massachusetts, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
 
  Funding: This work was supported by DARPA grant N66001-11-1-4192, CFEL DESY, DOE grants DE-FG02-10ER46745, and NSF grant DMR-1042342.
X-ray free electron laser studies are presented that rely on a nanostructured electron beam interacting with a “laser undulator” configured in the head-on inverse Compton scattering geometry. The structure in the electron beam is created by a nanoengineered cathode that produces a transversely modulated electron beam. Electron optics demagnify the modulation period and then an emittance exchange line translates the modulation to the longitudinal direction resulting in coherent bunching at x-ray wavelength. The predicted output radiation at 1 keV from a 7 MeV electron beam reaches 10 nJ or 6X108 photons per shot and is fully coherent in all dimensions, a result of the dominant mode growth transversely and the longitudinal coherence imposed by the electron beam nanostructure. This output is several orders of magnitude higher than incoherent inverse Compton scattering and occupies a much smaller phase space volume, reaching peak brilliance of 1027 and average brilliance of 1017 photons/(mm2 mrad2 0.1% sec).
 
 
WEPSO26 Status of the Flash Facility 550
 
  • K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt
    DESY, Hamburg, Germany
 
  The free-electron laser user facility FLASH at DESY (Hamburg, Germany)finished its 4th user period in February 2013. In total 2715 hours of SASE radiation has been delivered to user experiments with photon wavelengths between 4.2 nm and 44 nm with up to 5000 photon pulses per second. After a shutdown to connect the second undulator line - FLASH2 - to the FLASH linac, and a following commissioning period, FLASH is scheduled to continue user operation in October 2013. The year 2014 will be dedicated to the 5th period of user experiments. The commissioning of FLASH2 will take place in 2014 parallel to FLASH1 user operation.  
 
WEPSO27 Recent LCLS Performance From 250 to 500 eV 554
 
  • R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou
    SLAC, Menlo Park, California, USA
  • P. Emma
    LBNL, Berkeley, California, USA
  • R. Soufli
    LLNL, Livermore, California, USA
 
  Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES.
The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV.
[1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho-
ton. 4(9), 641–647 (2010).
 
 
WEPSO44 Design Studies for FLUTE, A Linac-based Source of Terahertz Radiation 598
 
  • S. Naknaimueang, V. Judin, S. Marsching, A.-S. Müller, M.J. Nasse, R. Rossmanith, R. Ruprecht, M. Schreck, M. Schuh, M. Schwarz, M. Weber, P. Wesolowski
    KIT, Karlsruhe, Germany
  • W. Hillert, M. Schedler
    ELSA, Bonn, Germany
 
  FLUTE is a linac-based THz source with nominal beam energy of 40-50 MeV which is presently under construction at KIT. It will be operated in a wide bunch charge range and will use different electron bunch compression schemes. The source will also study different mechanisms of radiation generation and serve as a test facility for related accelerator technology. This contribution presents the results of an overall optimization of the accelerator and a bunch compressor. A usage of a dispersive compressor and a velocity buncher, as well as combination of both are discussed. It is shown that bunch lengths in the range of a few femtoseconds can be achieved at very low bunch charges, while nC-bunches can be compressed down to approximately 200 fs. The utilization of both schemes results in high THz radiation fields at the experimental port.  
 
WEPSO53 Harmonic Lasing at the LCLS 623
 
  • D.F. Ratner, Z. Huang, P.A. Montanez
    SLAC, Menlo Park, California, USA
  • E. Allaria
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • W.M. Fawley, L.N. Rodes
    LBNL, Berkeley, California, USA
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Funding: Department of Energy
The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system.
*B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006)
**E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012)
 
 
WEPSO59 A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm 646
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. We demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 1031 photons/(s  mrad2  mm2  0.1%  BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation.  
 
WEPSO60 A Method for Obtaining High Degree of Circular Polarization at X-ray FELs 651
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Baseline design of many X-ray FEL undulators assumes a planar configuration which results in a linear polarization of SASE FEL radiation. However, many users experiments would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a helical afterburner, but then one should have an efficient method to suppress linearly polarized background from the main undulator. In this paper we consider a new method for such a suppression which is illustrated with the parameters of the soft X-ray undulator SASE3 of the European X-ray FEL.  
 
WEPSO67 Progress with the FERMI Laser Heater Commissioning 680
 
  • S. Spampinati, E. Allaria, D. Castronovo, M. Dal Forno, M.B. Danailov, G. De Ninno, A.A. Demidovich, S. Di Mitri, B. Diviacco, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, G. Penco, C. Spezzani, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  FERMI@ELETTRA is a seeded free electron laser facility composed by one linac and two FEL lines named FEL-1 and FEL-2. FEL-1 works in HGHG configuration, while FEL2 is a HGHG cascade implementing "fresh bunch" injection into the second stage. Perfomance of FEL-1 and FEL-2 lines have benefited from the use of the laser heater system, which is located right after the injector, at 100 MeV beam energy. Proper tuning of the laser heater parameters has allowed control of the microbunching instability, which is otherwise expected to degrade the high brightness electron beam quality sufficiently to reduce the FEL power. The laser heater was commissioned one year ago and positive effects upon microbunching instabilities and FEL-1 performance was soon observed. In this work we presents further measurements of microbunching suppression in two compressors scheme showing directly the reduction of beam slice energy spread due to laser heater action. We present measuerements showing the impact of the laser heater on FEL2  
 
WEPSO68 Effect of Coulomb Collisions on Echo-enabled Harmonic Generation 684
 
  • G.V. Stupakov
    SLAC, Menlo Park, California, USA
 
  Echo Enabled Harmonic Generation (EEHG) for FEL seeding is sensitive to the intrabeam scattering (IBS) effect. The reason for this is that in the process of generation high-harmonic density modulation in the beam the phase space evolves through a stage with narrow energy bands, which are characterized by the energy spread many times smaller than the beam energy spread. Energy diffusion caused by IBS tends to smear our these bands leading to diminished bunching factors at high harmonics. In the previous work [1] IBS in EEHG was studied in a simple model of a drift. This work extends the analysis of [1] to realistic lattices, and is applied to some of the existing practical designs of EEHG seeding.
[1] G. Stupakov, Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG), in Proceedings of the 2011 FEL Conference, Shanghai, China, 2011.
 
 
WEPSO78 Harmonic Lasing Self-seeded FEL 700
 
  • M.V. Yurkov, E. Schneidmiller
    DESY, Hamburg, Germany
 
  In this paper we perform analysis of capabilities of SASE FELs at the European XFEL for generation of narrow band radiation. An approach based on application of harmonic lasing self-seeding (HLSS) is under study[*]. Effective harmonic lasing occurs in the exponential gain regime in the first part of the undulator, making sure that the fundamental frequency is well below saturation. In the second part of the undulator the value of undulator parameter is reduced such that now the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is defined by the harmonic lasing (i.e. it is reduced by a significant factor depending on harmonic number) but the saturation power is still as high as in the reference case of lasing at the fundamental, i.e. brilliance increases. Application of the undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15, 080702 (2012)
 
 
WEPSO80 Coherence Properties of the Radiation From FLASH 704
 
  • M.V. Yurkov, E. Schneidmiller
    DESY, Hamburg, Germany
 
  Several user groups at FLASH use higher odd harmonics (3rd and 5th) of the radiation in experiments. Some applications require knowledge of coherence properties of the radiation at he fundamental and higher harmonics. In this paper we presents results of the studies of coherence properties of the radiation from FLASH operating at radiation wavelength of 6.x nm at the fundamental harmonic, and higher odd harmonics (2.x nm and 1.x nm) at electron energy of 1 GeV.  
 
THIBNO01
Methods for Achieving Spectral Purity in SASE FELs  
 
  • J. Wu
    SLAC, Menlo Park, California, USA
 
  Pushed forward by the advent of external seeding FELs, SASE FEL facilities are searching new techniques for achieve comparable spectral purity, while taking advantage of the relatively simpler SASE hardware configuration. A review of the most interesting techniques for cleaning the SASE spectrum is given.  
slides icon Slides THIBNO01 [3.284 MB]  
 
THIBNO02
Demonstration Of Two-color XFEL Operation and Autocorrelation Measurement at SACLA  
 
  • T. Hara, Y. Inubushi, T. Ishikawa, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Katayama, T. Togashi, K. Tono
    JASRI/SPring-8, Hyogo, Japan
  • T. Sato
    The University of Tokyo, Tokyo, Japan
 
  Recently two-color XFEL operation with a relative wavelength separation of 30 % has been achieved at SACLA in hard x-rays. In the two-color operation at SACLA, a simple and lucid scheme is employed, namely the first and second halves of the undulators are set at different K values. To make a time delay between the two-color photon pulses, a magnetic chicane is installed between the two undulator sections to detour the electron beam. Since the two-color pulses are emitted from the same electron bunch, there is no time jitter and the delay can be finely adjusted up to 40 fs. Two wavelengths can be freely selected in hard x-rays. The photon pulse length of the single-color operation measured by an autocorrelation technique is less than 10 fs (FWHM). The two-color operation of SACLA, which provides femtoseconds-short pulses with a GW-level peak power, is an ideal light source for x-ray pump x-ray probe experiments.  
slides icon Slides THIBNO02 [1.988 MB]  
 
THOBNO01 Three Unique FEL Designs for the Next Generation Light Source 734
 
  • G. Penn, D. Arbelaez, J.N. Corlett, P. Emma, G. Marcus, S. Prestemon, M.W. Reinsch, R.B. Wilcox
    LBNL, Berkeley, California, USA
  • A. Zholents
    ANL, Argonne, USA
 
  The NGLS is a next generation light source initiative spearheaded by the Lawrence Berkeley National Laboratory and based on an array of free-electron lasers (FEL) driven by a CW, 1-MHz bunch rate, superconducting linear accelerator. The facility is being designed to produce high peak and high average brightness coherent soft x-rays in the wavelength range of 1-12 nm, with shorter wavelengths accessible in harmonics or in expansion FELs. The facility performance requirements are based on a wide spectrum of scientific research objectives, requiring high flux, narrow-to-wide bandwidth, broad wavelength tunability, femtosecond pulse durations, and two-color pulses with variable relative timing and polarization, all of which cannot be encompassed in one FEL design. In addition, the cost of the facility requires building in a phased approach with perhaps three initial FELs and up to 9-10 FELs in the long term. We describe three very unique and complimentary FEL designs here as candidates for the first NGLS configuration.  
slides icon Slides THOBNO01 [1.331 MB]  
 
THOBNO02 Transverse Gradient Undulators for a Storage Ring X-ray FEL Oscillator 740
 
  • R.R. Lindberg, K.-J. Kim
    ANL, Argonne, USA
  • Y. Cai, Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Dept.~of Energy, Office of Basic Energy Sciences, Contract No.~DE-AC02-06CH11357.
An x-ray FEL oscillator (XFELO) is a fully coherent 4th generation source with complementary scientific applications to those based on self-amplified spontaneous emission*. While the naturally high repetition rate, intrinsic stability, and very small emittance produced by an ultimate storage ring (USR) makes it a potential candidate to drive an XFELO, the energy spread is typically an order of magnitude too large for sufficient gain. On the other hand, Smith and coworkers** showed how the energy spread requirement can be effectively mitigated with a transverse gradient undulator (TGU): since the TGU has a field strength that varies with transverse position, by properly correlating the electron energy with transverse position one can approximately satisfy the FEL resonance condition for all electrons. Motivated by recent work in the high-gain regime***, we investigate the utility of a TGU for low gain FELs at x-ray wavelengths. We find that a TGU may make an XFELO realizable in the largest ultimate storage rings now under consideration (e.g., in either the old Tevatron or PEP-II tunnel).
* K.-J. Kim, Y. Shvyd'ko and S. Reiche, PRL 100 244802 (2008).
** T. Smith, et al., J. Appl. Phys. 50, 4580 (1979).
*** Z. Huang, Y. Ding, and C.B. Schroeder, PRL 109, 204801 (2012).
 
slides icon Slides THOBNO02 [1.208 MB]