FEL Technology III: Undulators, Beamlines, Beam Diagnostics
Paper Title Page
TUIBNO01
 Beamline Instrumentation for Precise Characterization of X-ray FELs  
 
  • M. Yabashi, Y. Inubushi, T. Sato, K. Tono
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  
  Precise diagnostic instruments for coherent X-ray pulses will be presented. In SACLA XFEL beamline, a high-resolution single-shot spectrometer (*), a timing monitor between XFEL beams and optical laser pulses (**), etc. have been　developed and utilized for user experiments. The resolution of the spectrometer was confirmed to be 14 meV and a spectral spike of ~ 100 meV width was measured. The XFEL pulse duration was estimated to be 4.5 - 31 fs from this spectrometer depending on the bunch compression condition (*). The time jitter between an XFEL and an optical laser was appropriately measured to be ~ 100 fs STD by using the timing monitor (**). The design and performance of other beamline instruments will be also presented.
*) Y. Inubushi, et al., Physical Review Letters 109, 144801 (2012)
**) T. Sato, et al., Proceedings of SRI 2012, THIC02 (2012) 		 
slides icon Slides TUIBNO01 [5.870 MB]  
 
TUOBNO01 Beam Diagnostics for Coherent Optical Radiation Induced by the Microbunching Instability 169
 
  • A.H. Lumpkin
    Fermilab, Batavia, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The generation of the ultrabright beams required by modern free-electron lasers (FELs) has generally relied on chicane-based bunch compressions that often result in the microbunching instability. Following compression, spectral enhancements can extend even into the visible wavelengths through the longitudinal space charge impedances. Optical transition radiation (OTR) screens have been extensively used for transverse electron beam size measurements for the bright beams, but the presence of longitudinal microstructures (microbunching) in the electron beam or the leading edge spikes can result in strong, localized coherent enhancements (COTR) that mask the actual beam profile. We now have evidence for the effects in both rf photocathode-gun injected linacs* and thermionic-cathode-gun injected linacs**. Since the first observations, significant efforts have been made to characterize, model, and mitigate COTR effects on beam diagnostics. An update on the state-of-the-art for diagnosing these effects will be given as illustrated by examples at APS, LCLS, SCSS, SACLA, and NLCTA.
*A.H. Lumpkin et al.,Phys. Rev. ST Accel. Beams 12, 040704 (2009).
**H. Tanaka,"Commissioning of the Japanese XFEL at Spring8, Proceedings of IPAC2011, San Sebastián, Spain, 21-25 (2011). 		 
slides icon Slides TUOBNO01 [1.805 MB]  
 
TUOBNO02
 Optical-EUV Pump and Probe Experiments With Variable Polarization on the Newly Open LDM Beamline of FERMI@Elettra  
 
  • P. Finetti, R. Borghes, C. Callegari, P. Cinquegrana, M.B. Danailov, A.A. Demidovich, C. Fava, S. Gerusina, C. Grazioli, R. Ivanov, G. Kurdi, M. Lonza, N. Mahne, I. Nikolov, L. Pivetta, O. Plekan, L. Raimondi, P. Sigalotti, C. Svetina, D. Zangrando, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • L. Avaldi, P. Bolognesi, M. Coreno, P. O’Keeffe
    CNR - IMIP, Trieste, Italy
  • G. De Ninno
    University of Nova Gorica, Nova Gorica, Slovenia
  • M. Di Fraia
    Università degli Studi di Trieste, Trieste, Italy
  • M. Ilchen, T. Mazza, M. Meyer, A.J. Rafipoor
    XFEL. EU, Hamburg, Germany
  • K. Ueda
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
  
  Two color experiments are now available to users at the low-density matter beamline (LDM) operating at the Free Electron Laser (FEL) source FERMI@Elettra [1]. The seeded FEL method used at FERMI allows generation of high power, coherent pulses in the femtosecond regime, with a high level of shot-to-shot stability. Variable polarization is also available. LDM is dedicated to atomic, molecular and cluster physics. The LDM end-station, equipped with a velocity map imaging and a time-of-flight detector [2], is an ideal tool to characterize fast multiphoton processes. LDM was open to users in December 2012 and in February 2013 performed its first pump and probe experiment on photoionization of atomic He and generation of spectral sidebands. The FERMI FEL-1 source, delivered EUV photons with several tens of microjoule per pulse (about 100 fs wide) in a tunable wavelength range from 65 to 20 nm, while the 780 nm, optical pulses were from the same Ti:sapphire laser used to form the FEL seed pulse. This paper gives details about the pump and probe experimental setup and shows the straightforward use of the pump and probe data to measure the FEL pulse width.
[1] E. Allaria et al., Nature Photonics, 6, 699 (2012).
[2] V. Lyamayev et al., J. Phys B: At. Mol. Opt. Phys.-B/466820/SPE/12380
 		 
slides icon Slides TUOBNO02 [3.956 MB]  
 
TUOBNO03 An RF Deflecting Cavity Based Spreader System for Next Generation Light Sources 173
 
  • C. Sun, L.R. Doolittle, P. Emma, J.-Y. Jung, M. Placidi, A. Ratti
    LBNL, Berkeley, California, USA
  
  Lawrence Berkeley National Laboratory (LBNL) is developing design concepts for a multi-beamline (up to 10 lines) soft x-ray FEL array powered by a superconducting linear accelerator with a high bunch repetition rate of approximately one MHz. The FEL array requires a beam spreader system which can distribute individual electron bunches from the linac to each independently configurable beamline. We propose a new spreader system using RF deflecting cavities to deflect electron bunches as an alternative design to the fast kicker scheme. This RF approach offers more stable deflection amplitude while removing the limitations on the bunch repetition rate characteristic of the kicker approach. In this work, we describes the design concept of this RF based spreader system, including technical choices, design parameters and beamline optics.
[1] M. Placidi et al., Proceedings of IPAC2012, New Orleans, Louisiana, USA, pp.1765-1767 		 
slides icon Slides TUOBNO03 [1.391 MB]  
 
TUOBNO04
 Femtosecond Electron and X-ray Beam Temporal Diagnostics Using an X-band Transverse Deflector at LCLS  
 
  • Y. Ding, C. Behrens, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, T.J. Maxwell, J.W. Wang, M.-H. Wang, J.J. Welch
    SLAC, Menlo Park, California, USA
  • C. Behrens
    DESY, Hamburg, Germany
  
  X-ray free-electron lasers provide ultrashort x-ray pulses for multidisciplinary users. Temporal characterization of these ultrashort pulses with a femtosecond precision remains a challenging topic. At the Linac Coherent Light Source (LCLS), an X-band radio-frequency transverse deflector proposed in 2011 [*] has just been installed and commissioning of the RF system has started. By measuring the electron beam longitudinal phase space between lasing and non-lasing conditions, both the e-beam and x-ray temporal profiles can be reconstructed. We report the latest progress of the commissioning of the deflector and the measurements on the e-beam and x-ray pulse length with this deflector at LCLS. The resolution, stability and operational performance will also be discussed.
[*] Y. Ding et al., Phys. Rev. ST Accel. Beams 14, 120701 (2011) 		 
slides icon Slides TUOBNO04 [4.086 MB]  
 
TUPSO14 Transverse Deflecting Structures for Bunch Length and Slice Emittance Measurements on SwissFEL 236
 
  • P. Craievich, R. Ischebeck, F. Löhl, G.L. Orlandi, E. Prat
    PSI, Villigen PSI, Switzerland
  
  The SwissFEL project, under development at the Paul Scherrer Institut, will produce FEL radiation in a wavelength range from 0.1 nm to 7 nm. The facility consists of an S-band rf-gun and booster, and a C-band main linac which accelerates the beam up to 5.8 GeV. Two magnetic chicanes will compress the beam between 2.5 fs rms and 25 fs rms depending on the operation mode. The bunch length and slice parameters will be measured after the first bunch compressor (330 MeV) by using an S-band transverse deflecting structure (TDS). A C-band TDS will be employed to measure the longitudinal parameters of the beam just upstream the undulator beamline (5.8 GeV). With the designed transverse beam optics, an integrated deflecting voltage of 70 MV is required in order to achieve a longitudinal resolution on the femtosecond time scale. In this paper we present the TDS measurement systems to be used at SwissFEL, with a particular emphasis on the new C-band device, including hardware, lattice layout and beam optics.  
 
TUPSO15 Beam Diagnostic Requirements for the Next Generation Light Source 242
 
  • S. De Santis, J.M. Byrd, J.N. Corlett, P. Emma, D. Filippetto, M. Placidi, H.J. Qian, F. Sannibale
    LBNL, Berkeley, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The NGLS project consists in a 2.4 GeV superconducting linac accelerating sub-1 μm normalized emittance bunches used to produce high intensity soft X-ray short pulses from multiple FEL beamlines. The 1 MHz bunch repetition rate, and the consequent high beam power, present special challenges, but also opportunities, in the design of the various electron beam diagnostic devices. The wide range of beam characteristics, from the photoinjector to the undulators, require the adoption of different diagnostics optimized to each machine section and to the specific application of each individual measurement. In this paper we present our plans for the NGLS beam diagnostics, discussing the special requirements and challenges. 		 
 
TUPSO22 Status of SwissFEL Undulator Lines 263
 
  • R. Ganter, M. Aiba, H.-H. Braun, M. Calvi, P. Heimgartner, G. Janzi, H. Jöhri, R. Kobler, F. Löhl, M. Negrazus, L. Patthey, E. Prat, S. Reiche, S. Sanfilippo, U. Schaer, T. Schmidt, L. Schulz, V. Vranković, J. Wickstroem
    PSI, Villigen PSI, Switzerland
  
  An overview of the Aramis Hard-X ray FEL line of SwissFEL is presented, showing its future integration in the tunnel as well as the space reservation for possible future upgrades: Athos Soft X-ray FEL line, post-undulator deflecting cavities. The design of the FEL components like the energy collimator, the matching sections or the dog leg transfer line linking the linac to the future Athos line are almost completed. The characterization of the in-vacuum undulator prototype is described in a companion paper. The installation of the components will start in spring 2015 while the first photons are planned for December 2016 with the alignment and adjustment of the undulators foreseen for first SASE operation by spring 2017 .  
 
TUPSO27 Design for a Fast, XFEL-Quality Wire Scanner 276
 
  • M.A. Harrison, R.B. Agustsson, T.J. Campese, P.S. Chang, A.Y. Murokh, M. Ruelas
    RadiaBeam, Santa Monica, USA
  
  RadiaBeam Technologies has designed and manufactured a new wire scanner for high-speed emittance measurements of XFEL-type beams of energy 139 MeV. Using three 25-micron thick tungsten wires, this wire scanner measures vertical and horizontal beam size as well as transverse spatial correlation in one pass. The intensity of the beam at a wire position is determined from emitted bremsstrahlung photons as measured by a BGO scintillator system. The wires are transported on a two-ended support structure moved by a ball-screw linear stage. The double-ended structure reduces vibrations in the wire holder, and the two-bellows design negates the effects of air pressure on the motion. The expected minimum beam size measurable by this system is on the order of 10 microns with 0.1-micron accuracy. To achieve this, new algorithms are presented that reduce the effect of the non-zero thickness of the wire on the wire scan output. In addition, novel calculations are presented for determining the elliptical geometric parameters (vertical and horizontal beam size and correlation, or alternatively, the axis lengths and rotation) of the beam from the wire scanner measurements.  
 
TUPSO42 Shimming Strategy for the Phase Shifters Used in the European XFEL 313
 
  • Y. Li, J. Pflüger, F. Wolff-Fabris
    XFEL. EU, Hamburg, Germany
  • H.H. Lu, Y.F. Yang
    IHEP, Beijing, People's Republic of China
  
  The undulator systems of the European XFEL need a total of 91 Phase Shifters. The 1st field integral of these devices must not exceed 0.004Tmm for working gaps > 16mm. For smaller gaps it is slightly released. In spite of the highly magnetically symmetric design and considerable effort such as the selection and sorting of the magnets small 1st field integral errors cannot be excluded. In this paper a strategy is studied to correct small gap dependent kicking errors as expected for the phase shifters of the XFEL. EU.by using shims of different geometries and sizes. It is found, that small gap dependent kicking errors can well be corrected for using this method. This is a systematic effort to provide effective fast tuning methods, which can be applied for the mass production. The meaning of shim signature will be explained in this paper. The method is demonstrated by simulations and measurements.  
 
TUPSO45 Initial Streak Camera Measurements of the S-band Linac Beam for the University of Hawaii FEL Oscillator 325
 
  • A.H. Lumpkin
    Fermilab, Batavia, USA
  • M.R. Hadmack, J.M.D. Kowalczyk, J. Madey, E.B. Szarmes
    University of Hawaii, Honolulu, HI, USA
  
  Funding: Work at Fermilab supported by Fermi Research Alliance, LLC under U.S.DOE Contract No.DE-AC02-07CH11359. Work at UH supported by U.S. Dept. of Homeland Security grant No. 20120-DN-077-AR1045-02.
The S-band linac driven Mark V free-electron laser oscillator (FELO) at the University of Hawai‘i operates in the mid-IR at electron beam energies of 40-45 MeV with a four microsecond macropulse length. Recently investigations of the electron beam micropulse bunch length and phase as a function of macropulse time became of interest for potentially optimizing the FELO performance. These studies involved the implementation of a Hamamatsu C5680 streak camera with dual sweep capabilities and the transport of optical transition radiation (OTR) generated at an upstream Cu mirror and of coherent spontaneous emission radiation (CSER) generated in the undulator to the streak camera location outside of the linac tunnel. Both a fast single-sweep vertical unit and a synchroscan unit tuned to 119.0 MHz were used. Initial results include measurements of the individual CSER (on the FEL7th harmonic at 652 nm) micropulse bunch lengths (3 to 5 ps FWHM), the CSER signal intensity variation along macropulse time, and a detected phase slew of 4 ps over the last 700 ns of the macropulse. Complementary OTR measurements are also being evaluated and will be presented as available. 		 
 
TUPSO47 First Results of a Longitudinal Phase Space Tomography at PITZ 334
 
  • D. Malyutin, M. Groß, I.I. Isaev, M. Khojoyan, G. Kourkafas, M. Krasilnikov, B. Marchetti, F. Stephan, G. Vashchenko
    DESY Zeuthen, Zeuthen, Germany
  
  The Photo Injector Test facility at DESY, Zeuthen Site (PITZ), was established as a test stand of the electron source for FLASH and the European X-ray Free Electron Laser (XFEL). One of the tasks at PITZ is the detailed characterization of longitudinal properties of the produced electron bunches. The measurements of the electron bunch longitudinal phase space can be done by tomographic methods using measurements of the momentum spectra by varying the electron bunch energy chirp. At PITZ the energy chirp of the electron bunch can be changed by varying the RF phase of the accelerating structure downstream the gun. The resulting momentum distribution can be measured in a dispersive section installed downstream the accelerating structure. The idea of the measurement and the tomographic reconstruction technique is described in this paper. The setup and first measurement results of the bunch longitudinal phase space measurements using the tomographic technique for several electron bunch charges, including 20 pC, 100 pC and 1 nC, are presented as well.  
 
TUPSO52 R&D Towards a Delta-type Undulator for the LCLS 348
 
  • H.-D. Nuhn, S.D. Anderson, G.B. Bowden, Y. Ding, G.L. Gassner, Z. Huang, E.M. Kraft, Yu.I. Levashov, F. Peters, F.E. Reese, J.J. Welch, Z.R. Wolf, J. Wu
    SLAC, Menlo Park, California, USA
  • A.B. Temnykh
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  The LCLS generates linearly polarized, intense, high brightness x-ray pulses from planar fixed-gap undulators. While the fixed-gap design supports a very successful and tightly controlled alignment concept, it provides only limited taper capability (up to 1% through canted pole and horizontal position adjustability) and lacks polarization control. The latter is of great importance for soft x-ray experiments. A new compact undulator design (Delta) has been developed and tested with a 30-cm-long in-vacuum prototype at Cornell University, which adds those missing properties to the LCLS undulator design and is readily adapted to the LCLS alignment concept. Tuning Delta undulators within tight, FEL type tolerances is a challenge due to the fact that the magnetic axis and the magnet blocks are not easily accessible for measurements and tuning in the fully assembled state. An R&D project is underway to install a 3.2-m long out-of-vacuum device in place of the last LCLS undulator, to provide controllable levels of polarized radiation and to develop measurement and tuning techniques to achieve x-ray FEL type tolerances. Presently, the installation of the device is scheduled for August 2013.  
 
TUPSO54 Undulators for Free Electron Lasers 351
 
  • C.W. Ostenfeld, M. Pedersen
    Danfysik A/S, Taastrup, Denmark
  
  Danfysik has produced insertion devices for the FEL community for almost 10 years. In this poster, we describe two recent undulator deliveries: a 2.8 m long undulator for the FELIX free electron laser, and a 4.5 m device for the FLARE project, both at Radboud University in Nijmegen, in the Netherlands. The device for FELIX is a 2.8 m PPM device, with a peak field of 0.483 T, and a minimum gap of 22 mm. The device for FLARE, is a 4.5 m hybrid device, with special poles, which allow for double focusing. For both devices, we describe the magnetic modelling, and the magnetic performance.  
 
TUPSO55 300 mm Electromagnetic Wiggler for ELBE 353
 
  • C.W. Ostenfeld, M. Pedersen
    Danfysik A/S, Taastrup, Denmark
  
  Danfysik has designed and built a 300 mm fixed-gap electromagnetic wiggler for the ELBE radiation source at Helmholz Zentrum Dresden Rossendorff. This wiggler will serve as a source of narrow-band THz radiation in the 100 μm to 10 mm range. Due to careful magnetic modelling, and an effective shimming process, we were able to deliver magnetic performance at a high level. We present the details of the modelling, as well as magnetic results.  
 
TUPSO60 Status of the Undulator Systems for the European X-ray Free Electron Laser 367
 
  • J. Pflüger, M. Bagha-Shanjani, A. Beckmann, K.H. Berndgen, P. Biermordt, G. Deron, U. Englisch, S. Karabekyan, B. Ketenoğlu, M. Knoll, Y. Li, F. Wolff-Fabris, M. Yakopov
    XFEL. EU, Hamburg, Germany
  
  The three undulator systems for the European XFEL consist of a total of 91 Undulator Cells. Each cell consists of an Undulator Segment and an intersection. They will be operational by end of 2015. The serial production of the 91 Undulator Segments is a great challenge and without precedence. It is now in full swing. This contribution gives an overview over the most important design aspects as well as the experience and strategy with the serial production. Representative results of magnetic performance are given. The status of the other system components is briefly described.  
 
TUPSO62 Status of the Planar Undulator Applied in HUST THz-FEL Oscillator 372
 
  • B. Qin, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang
    HUST, Wuhan, People's Republic of China
  • Y.B. Wang
    Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
  
  To fulfill the physical requirement of a 50-100 um Free Electron Laser (FEL) oscillator, design considerations of a planar undulator are described. Some technical issues, including the tolerances study, the beam match, the field measurement setup and the influence on the magnetic field by the waveguide are discussed as well.  
 
TUPSO66 Transport of Terahertz-Wave Coherent Synchrotron Radiation With a Free-electron Laser Beamline at LEBRA 383
 
  • N. Sei, H. Ogawa
    AIST, Tsukuba, Ibaraki, Japan
  • K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
    LEBRA, Funabashi, Japan
  
  Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696.
Nihon University and AIST have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator, and confirmed it to be CSR*. To avoid a damage caused by ionizing radiation, we worked on transporting the CSR to an experimental room which was next to the accelerator room. By using a beamline of an infrared free-electron laser, the CSR more than 1 mW was successfully transported to the experimental room. The transport of the CSR and imaging experiments with the CSR at LEBARA will be reported.
*: N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104. 		 
 
TUPSO74 A Coaxially Coupled Deflecting-accelerating Mode Cavity System for Phase-space Exchange (PSEX) 395
 
  • Y.-M. Shin, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.D. Church
    Fermilab, Batavia, USA
  • J.H. Park, A.M.M. Todd
    AES, Princeton, New Jersey, USA
  
  A feasible method to readily remove energy spread (R56 term) due to thick lens effect of a deflecting mode RF-cavity has been widely investigated for emittance exchange in 6D phase-space*,**. By means of theoretical calculation and numerical analysis, it was found that an accelerating cavity effectively cancel the longitudinal phase space chirp. We have extensively investigated the combined deflecting-accelerating mode phase-space exchanger with the simple RF distribution system of the beam-pipe coaxial coupler. EM simulations proved the coupling scheme with eigenmode and S-parameter analyses. Currently we are looking into 3D beam dynamics in the system with tracking/particle-in-cell (PIC) simulations and wakefield analysis. Proof-of-concept (POC) experiment is planned with a high-Q normal conducting cavity built in a cryogenic cooling system (liquid nitrogen) in Fermilab.
* P. Emma, et. al., Phys. Rev. ST Accel. Beams 9, 100702 (2006)
** Zholents and M. Zolotorev, LBNL CBP Seminar (2010) and No. ANL/APS/LS-327(2011)
 		 
 
TUPSO77 Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field 406
 
  • N.V. Smolyakov, S.I. Tomin
    NRC, Moscow, Russia
  • G. Geloni
    XFEL. EU, Hamburg, Germany
  
  In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.  
 
TUPSO81 Challenges for Detection of Highly Intense FEL Radiation: Photon Beam Diagnostics at FLASH1 and FLASH2 417
 
  • K.I. Tiedtke, M. Braune, G. Brenner, S. Dziarzhytski, B. Faatz, J. Feldhaus, B. Keitel, M. Kuhlmann, H. Kühn, E. Plönjes, A.A. Sorokin, R. Treusch
    DESY, Hamburg, Germany
  
  In spite of the evident progress in the development of FEL facilities, the characterization of important FEL photon beam parameters during FEL-commissioning and user experiments is still a great challenge. In particular pulse-resolved photon beam characterization is essential for most user experiments, but the unique properties of FEL radiation properties such as extremely high peak powers and short pulse lengths makes the shot-to-shot monitoring of important parameters very difficult. Therefore, sophisticated concepts have been developed and used at FLASH in order to measure radiation pulse intensity, beam position and spectral as well as temporal distribution – always coping with the highly demanding requirements of user experiments as well as machine operation. Here, an overview on the photon diagnostic devices operating at FLASH and FLASH II will be presented, with emphasizes on the pulse resolving intensity and energy detectors based on photoionization of rare gases.  
 
TUPSO87 High-Field Laser-Based Terahertz Source for SwissFEL 438
 
  • C. Vicario, C.P. Hauri, B. Monoszlai, C. Ruchert
    PSI, Villigen PSI, Switzerland
  • C.P. Hauri
    EPFL, Lausanne, Switzerland
  
  We present efficient laser-driven THz generation by optical rectification in various organic materials yielding transient fields up to 150 MV/m and 0.5 Tesla. The generated spectra extend over the entire THz gap (0.1-10 THz). Manipulation of the absolute phase by dispersion control is demonstrated for 5-octave spanning, single-cycle pulses. The presented source will be applied to the future SwissFEL as Xray photon temporal diagnostics and for pump-and-probe experiments.  
 
TUPSO89 A Femtosecond Resolution Electro-optic Diagnostic Using a Nanosecond-pulse Laser 447
 
  • D.A. Walsh, W.A. Gillespie
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • S.P. Jamison
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S.P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Funding: This project has been funded by CERN as part of the CLIC-UK programme Contract Number KE1865/DG/CLIC
Electro-optic diagnostics with a target time resolution of 20fs RMS, and with intrinsically improved stability and reliability, are being developed. The new system is based on explicit temporal measurement of an electro-optically upconverted pulse, following interaction of the bunch with a quasi-CW probe pulse. The electro-optic effect generates an “optical-replica” of the longitudinal charge distribution from the narrow-bandwidth probe, simultaneously up-converting the bunch spectrum to optical frequencies. By using Frequency Resolved Optical Gating (FROG), an extension of autocorrelation, the optical replica can then be characterised on a femtosecond time scale. This scheme therefore bypasses the requirement for unreliable femtosecond laser systems. The high pulse energy required for single-shot pulse measurement via FROG will be produced through optical parametric amplification of the optical-replica pulses. The complete system will be based on a single nanosecond-pulse laser – resulting in a reliable system with greatly relaxed timing requirements. 		 
 
TUPSO91 FEL R&D Within LA3NET 452
 
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: Work supported by the EU under Grant Agreement 289191.
The detailed diagnostics of the shortest beam pulses in free-electron lasers still pose significant challenges to beam instrumentation. Electro-optical methods are a promising approach for the non-intercepting measurement of electron bunches with a time resolution of better than 50 fs, but suitable optical materials need to be better understood and carefully studied. In addition, adequate timing systems with stability in the fs regime based on mode-locked fibre laser optical clocks, and actively length-stabilised optical fibre distribution require further investigation. Within the EU-funded LA³NET project these important problems are being addressed by an international consortium of research centres, universities, and industry partners. This contribution gives an overview of the LA3NET project and results from initial studies in both areas. It also describes the events, such as schools, topical workshops and conferences that LA3NET will organize.