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| WEPD01 | Free Electron Lasers in 2012 | 369 |
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Funding: This work has been supported by the Office of Naval Research. Thirty-six 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. |
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| WEPD03 | The CSU Accelerator and FEL Facility | 373 |
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| The Department of Electrical and Computer Engineering recently received a donation of an L-band photocathode-gun and RF linear accelerator system from the University of Twente, the Netherlands. This system will be used for training and research and development of beam components. A description of the system configuration, estimated build-up schedule, and first experiments will be described. | ||
| WEPD04 | Status of the SOLEIL Femtosecond X-ray Source | 377 |
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| An electron bunch slicing setup is presently under construction on the SOLEIL storage ring. It is aimed to deliver 100 fs long photon pulses to two undulator-based beamlines operating with soft X-rays (TEMPO) and hard X-rays (CRISTAL). SOLEIL storage ring is equipped with a Ti:Sa laser which produces 30 fs pulses at 800 nm with a repetition rate of 2.5 kHz. The laser beam is splitted into two branches in order to provide 2 mJ to the modulator and 1 mJ as pump pulse for the CRISTAL and TEMPO end stations. Focusing optics and beam path, from the laser hutch to the inside of the storage ring tunnel are presently under finalization. The energy modulation will be done in a wiggler composed of 20 periods of 164 mm. It produces a magnetic field of 1.8 T at a minimum gap of 14.5 mm. The non-zero dispersion function present in all straight sections of the storage ring will enable to easily separate the sliced bunches from the core bunches at the beamlines' location. In this paper, we will report on the specificities of the SOLEIL setup, the status of its installation and the expected performances. | ||
| WEPD07 | Status of the FLASH II Project | 381 |
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| The extension of the FLASH facility at DESY (Hamburg, Germany) - FLASH II Project - is under way. The extension includes a second undulator line with variable gap undulators to allow a more flexible operation, and a new experimental hall for photon experiments. The present FLASH linac will drive the both undulator beamlines. Civil construction of the new buildings has been started in autumn 2011 continuing in several steps until early 2013. The design of the new beamline including the extraction from the FLASH linac and the undulator is mostly finished, and the manufacturing of the components is under way. The mounting of the beamline will start in autumn 2012, and the commissioning with beam is scheduled for second half of 2013. We report here the design of the different phases of the project including the time schedule up to the first user operation. | ||
| WEPD08 | Upgrades of the Photoinjector Laser System at FLASH | 385 |
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| The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate a 0.8 ms long train of thousands of electron bunches in a burst mode. This puts special demands on the design of the electron source, especially the laser system. The construction of a second undulator beamline FLASH2 has started. The pulse train will be divided into two parts to serve both beamlines simultaneously. Since experiments with the FLASH soft X-ray beam need flexibility, we plan to use two laser systems each serving one beamline. This makes it possible to deliver two trains with different properties in charge, number of bunches, and bunch spacing in the same RF pulse. This also required an upgrades of the laser beamline design. We report on improvements of the laser beamline and first tests operating two lasers simultaneously at FLASH. | ||
| WEPD09 | Scheme for Generating and Transporting THz Radiation to the X-ray Experimental Hall at the European XFEL | 389 |
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| We consider generation of THz radiation from the spent electron beam downstream of the SASE2 undulator in the electron beam dump area. The THz output must propagate at least for 250 meters through the photon beam tunnel to the experimental hall to reach the SASE2 X-ray hutches. We propose to use an open beam waveguide such as an iris guide as transmission line. In order to efficiently couple radiation into the iris transmission line, generation of the THz radiation pulse can be performed directly within the iris guide. The line transporting the THz radiation to the SASE2 X-ray hutches introduces a path delay of about 20 m. Since THz pump/X-ray probe experiments should be enabled, we propose to exploit the European XFEL baseline multi-bunch mode of operation, with 222 ns electron bunch separation, in order to cope with the delay between THz and X-ray pulses. We present start-to-end simulations for 1 nC bunch operation-parameters, optimized for THz pump/X-ray probe experiments. Detailed characterization of the THz and SASE X-ray radiation pulses is performed. Highly focused THz beams will approach the high field limit of 1 V/atomic size. | ||
| WEPD10 | Conceptual Design of an Undulator System for a Dedicated Bio-imaging Beamline at the European X-ray FEL | 393 |
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| We describe a future possible upgrade of the European XFEL consisting in the construction of an undulator beamline dedicated coherent diffraction imaging of complex molecules. Crucial parameters are photon energy range, peak power, and pulse duration. The peak power is maximized in the photon energy range between 3 keV and 12 keV by the use of a very efficient combination of self-seeding, fresh bunch and tapered undulator techniques. The unique combination of ultra-high peak power of 1 TW in the entire energy range, and ultrashort pulse duration tunable from 2 fs to 10 fs, would allow for single shot coherent imaging of protein molecules with size larger than 10 nm. Also, the new beamline would enable ima ing of large biological structures in the water window, between 0.3 and 0.4 keV. In order to make use of standardized components, at present we favor the use of SASE3-type undulator segments. The number segments, 40, is determined by the tapered length for the design output power of 1 TW. The present plan assumes the use of a nominal electron bunch with charge of 0.1 nC. Experiments would be performed without interference with the other three undulator beamlines. | ||
| WEPD11 | Dependence of FEL Intensity on the Available Number of Undulators for FERMI FEL-1 | 397 |
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| FERMI@Elettra is a free electron laser user facility based in Trieste Italy. The first FEL line (FEL-1), based on the high gain harmonic generation scheme, covers the spectral range from about 80nm down to 20nm with high quality FEL pulses and started producing FEL light for user operations in 2011. FERMI FEL-1 radiator is composed by six undulators 2.4meter long with the available space for additional two undulators. In this work we investigate the impact of additional undulators on the FEL performance in the case of FERMI FEL-1. We finally extend the work studying the dependence of the FEL power as a function of the length of the radiator for FELs based on the high gain harmonic generation scheme showing that for typical parameters there is a linear dependence. | ||
| WEPD12 | Status of the DELTA Short-Pulse Facility | 401 |
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Funding: Supported by DFG, BMBF, and the Federal State NRW Since 2011, a new Coherent Harmonic Generation (CHG) source* is under commissioning at the 1.5 GeV storage ring DELTA. Following first experiments using the fundamental wavelength of a Ti:sapphire laser for seeding a non-symmetrical optical klystron, 400 nm pulses from a second-harmonic conversion unit (SHG) are used since early 2012. With the radiator tuned to the second harmonic thereof, 200 nm CHG pulses are routinely observed. In order to detect higher harmonics and to proceed to a seed wavelength of 266 nm, an evacuated diagnostics beamline is under construction. Additionally, an existing VUV beamline is being upgraded to allow for the detection of the CHG pulses and their utilization in pump-probe experiments. Furthermore, a dedicated THz beamline provides valuable information about the laser-induced energy modulation of the electrons. In this paper, the status of the project and technical details will be presented. * Huck et.al., FEL 2011 |
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| WEPD13 | Beam Dynamics Design of the CLARA FEL Test Accelerator | 405 |
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| CLARA (Compact Linear Advanced Research Accelerator) is a proposed FEL test facility at Daresbury Laboratory in the UK. This is proposed to be a 250 MeV normal-conducting linac capable of producing short, high brightness electron bunches which can be synchronised with an external source. CLARA will build upon the EBTF photoinjector under construction at Daresbury, utilising the S-band RF electron gun. Bunch compression will be achieved via two methods: a variable magnetic chicane with fourth harmonic cavity, or velocity bunching in the low energy regime. CLARA will be capable of providing beams for various novel FEL schemes. | ||
| WEPD18 | Potential for Laser-induced Microbunching Studies with the 3-MHz-rate Electron Beams at ASTA | 409 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Investigations of the laser-induced microbunching as it is related to time-sliced electron-beam diagnostics and high-gain-harmonic generation (HGHG) free-electron lasers using bright electron beams are proposed for the Advanced Superconducting Test Accelerator (ASTA) facility at Fermilab. Initial tests at 40-50 MeV with an amplified 800-nm seed laser beam co-propagating with the electron beam through a short undulator (or modulator) tuned for the third-harmonic resonance condition followed by transport through a subsequent chicane will result in energy modulation and z-density modulation (microbunching), respectively. The latter microbunching will result in generation of coherent optical or UV transition radiation (COTR, CUVTR) at a metal converter screen which can reveal slice beam size, centroid, and energy spread. Additionally, direct assessment of the microbunching factors related to HGHG by measurement of the COTR intensity and harmonic content after the chicane as a function of seed laser power and beam parameters will be done. These experiments will be performed using the ASTA 1-MHz-rate micropulse train for up to 1ms which is unique to test facilities in the USA. |
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| WEPD19 | Design of a Proof-of-principle Experiment Toward the Generation of Coherent Optical Radiation using a 4-MeV Electron Beam | 413 |
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Transverse-to-longitudinal phase space exchange techniques have open new possibilities toward shaping the temporal distribution of electron bunches. Recently, the combination of such exchange methods with structured, e.g. field-emission, cathodes was suggested as the backbone of compact coherent short-wavelength sources [W. S. Graves, {\em et al.}, ArXiv:1202.0318 (2012)]. In this paper, we present the design and numerical investigation of a proof-of-principle experiment to produce coherent optical transition radiation using a ~4-MeV electron bunch. The optically-modulated bunch is produced from a structured cathode combined with a transverse-to-longitudinal phase space exchanger. The current status of the experiment are also summarized.
This work was supported by DOE grants DE-AC02-07CH11359, DE-FG02-08ER41532, and DARPA grant N66001-11-1-4192. |
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| WEPD20 | Time-Sliced Emittance and Energy Spread Measurements at FERMI@Elettra | 417 |
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| FERMI@Elettra is a single pass seeded FEL based on the high gain harmonic generation scheme, producing intense photon pulses at short wavelengths. For that, a high-brightness electron beam is required, with a small uncorrelated energy spread. In this paper, we present a detailed campaign of measurements aimed at characterizing the electron-beam time-sliced emittance and energy spread, both after the first magnetic compressor and at the end of the linac. | ||
| WEPD26 | Collective and Individual Aspects of Fluctuations in Relativistic Electron Beams for Free-Electron Lasers | 421 |
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Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 Fluctuations in relativistic electron beams for free-electron lasers (FELs) exhibit both collective and individual particle aspects, similar to that seen in non-relativistic plasmas. We show that the density fluctuations are described by a linear combination of the collective plasma oscillation and the random individual motion of Debye-screened dressed particles. The relative importance of the individual to the collective motion is determined by comparing the fluctuation length scale divided by two pi with the relativistic beam Debye length. Taking into account the fact that the velocity spread is caused by both the energy spread and the angular divergence, we derive a simple formula for the minimum value of the Debye length using a solvable 1-D model. For electron beams used for x-ray self-amplified spontaneous emission (SASE) we find that the Debye length is comparable to the radiation wavelength, and that therefore the collective motion is not relevant. |
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| WEPD28 | Electron Optics and Magnetic Chicane for Matching an XFEL-Oscillator Cavity into a Beamline at the European XFEL Laboratory | 425 |
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| At DESY the European XFEL (X-Ray Free-Electron Laser) laboratory is currently under construction. Due to the time structure of its electron bunch trains it is in principle possible to run a FELO (Free-Electron Laser Oscillator) at the European XFEL. The major elements of a FELO are the cavity and the undulator. To couple the electron beam with the required beta functions into the cavity, a magnetic chicane and an appropriate focusing structure are considered. In this paper we discuss the lattice design of the magnetic chicane and the focusing section. We also present the results of the beam dynamics simulations performed. | ||
| WEPD29 | Numerical Simulations of an XFELO for the European XFEL driven by a Spent Beam | 429 |
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| The European XFEL will be an X-ray free electron laser laboratory at DESY in Hamburg Germany. In the baseline design the light pulses will be generated in long undulators via the SASE process. The wavelengths of the light pulses will be between 5 nm and 0.05 nm. Since SASE pulses have a poor longitudinal coherence a lot of research is ongoing to overcome the statistical fluctuations of the SASE pulses. Some years ago Kim et al. proposed an FEL oscillator for light sources based on energy-recovery linacs (ERL), using Diamond Bragg crystals to perform a high reflective cavity in the X-ray regime (XFELO). Since the European XFEL will be based on superconducting accelerator structures it will deliver a long train of electron bunches which might be suitable to support an XFELO arrangement as well. In particular, the spent beam at the exit of a SASE FEL might be still qualified to drive an XFELO. Theoretical simulations of an oscillator based on Diamond crystals for the European XFEL will be presented using electron bunches of a spent beam. | ||
| WEPD30 | Simulations of XFELO for the KEK ERL | 433 |
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| Following the recent development of high-brightness electron guns and high-reflectivity X-ray crystal optics, an FEL oscillator operated in a hard X-ray wavelength region (XFELO) has been considered as a possible extension of the 3-GeV ERL light source proposed at KEK. In order to deliver a 6-GeV electron beam to the XFELO, the ERL is operated at the energy-doubling mode with a low average current. In this paper, we present results of electron beam simulations and FEL simulations. | ||
| WEPD31 | Sub-Ångström Stabilization of an X-ray Free Electron Laser Oscillator and Nuclear Resonance Metrology | 437 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A scheme is described to length-stabilize the cavity of an x-ray free-electron-laser oscillator (XFELO)* by keeping one of its longitudinal modes in nuclear resonance at 14.4 keV with a sample of 57Fe. The mode spacing corresponding a 100 m XFELO cavity is about 12 neV, which can be resolved with the 5 neV linewidth of 57Fe, even with some inhomogeneous line broadening. With a cavity thus stabilized, a standing-wave pattern can be maintained over hours, to be probed by another sample of 57Fe in a meter-long scan to compare the nuclear-resonant wavelength with a known optical standard. This should improve the relative accuracy of this wavelength from 10-7** to 10-11. Ensemble, or long-time averaging, as used in atomic clocks, can further increase the accuracy. Refining the scheme to other nuclear-resonant species with narrower resonances, such as 181Ta (6.2 keV, 75 peV), will open up precision x-ray metrology for technological and fundamental applications. * K.-J. Kim, Yu. Shvyd'ko, S. Reiche, Phys. Rev. Lett. 100, 244802 (2008);K.-J. Kim, Yu. Shvyd'ko, Phys. Rev. ST-AB, 030703 (2009) ** M. Lucht, dissertation, Hamburg (2005) |
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| WEPD32 | Injector System for Linac-based Infrared Free-electron Laser in Thailand | 441 |
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Funding: This work has been supported by the Department of Physics and Materials Science at Chiang Mai University, the Thailand Center of Excellence in Physics, and the Thailand Research Fund. A possibility to develop a compact linac-based Infrared Free-electron Laser (IR-FEL) facility has been studied at Chiang Mai University (CMU) in Thailand. Characteristics of the emitted FEL light and reliability in operation of the facility are determined by the properties of an electron injection system, an undulator, and an optical cavity. The proposed injector system for the future IR-FEL is based on the RF linear accelerator system at the Plasma and Beam Physics Research facility (PBP-linac) at CMU. However, the required electron beam properties for the IR-FEL are different from the current available electron beams from the PBP-linac. Numerical and experimental studies to modify the existing system to be able to drive the IR-FEL have been performed. The results of the studies and the proposed injector system parameters will be presented in this contribution. |
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| WEPD34 | Beam Dynamics Simulation and Optimization of Electron Beam Properties for IR-FELs at Chiang Mai University | 445 |
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Funding: This work has been supported by the Department of Physics and Materials Science at Chiang Mai University, the Thailand Center of Excellence in Physics, and the Thailand Research Fund. The linear accelerator system at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand, has been under a plan to extend its function to be an injector system for the Infrared Free-electron Lasers (IR-FELs). The current system consists of an S-band thermionic cathode RF-gun, a bunch compressor in a form of alpha-magnet and a 3-m SLAC-type linear accelerator. The current system will be modified to generate the electron beam with the properties suitable for the IR-FELs. Numerical simulations have been performed to investigate and optimize the electron beam parameters. The planned modification of the system and optimization of the electron beam parameters will be presented in this contribution. |
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| WEPD38 | Improvement of KU-FEL Performance by Replacing Undulator and Optical Cavity | 449 |
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A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences*. The FEL achieved first lasing and saturation in 2008**,***. However, the tunable range was limited from 10 to 13 micro-m because of insufficient macro-pulse duration of e-beam and FEL gain. The undulator of KU-FEL has been replaced with the undulator which was previously used for ERL-FEL in JAEA. The optical cavity has been replaced with optimized one. In addition the diameter of the coupling hole on the upstream cavity mirror has been reduced from 2 to 1 mm for reducing cavity loss. After installation, the tunable range of KU-FEL has been improved to 5-15 micro-m. Estimated FEL gain is greater than 30%, which was 1.5 times larger than original configuration.
*H. Zen, et al., Infrared Physics and Technology, Vol. 51, Issue 5, p.382 (2008) **H. Ohgaki, et al., Proc. of FEL08, p.4 (2008) ***H. Ohgaki, et al., Proc. of FEL09, p.572 (2009) |
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| WEPD39 | Status of IR-FEL at Tokyo University of Science | 453 |
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| IR-FEL research center of Tokyo University of Science (FEL-TUS) is a facility for aiming at development of the high performance FEL device and promotion of photo-sciences using it. The main part of FEL-TUS involves a mid-infrared FEL (MIR-FEL) which provides continuously tunable radiation in the range of 5 -14 um and a variety of experiments are by the use of this photon energy corresponding to the various vibrational modes of molecules are now underway. We also are making effort to develop a far-infrared FEL (FIR-FEL) in order to realize FEL lasing in the THz region. The status of research activities at FEL-TUS will be presented. | ||
| WEPD40 | Hole-coupling in IR FELs: An Experimental Study | 456 |
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Even though hole-coupling has been used for many years at several IR FEL facilities, its usefulness as outcoupling scheme has recently been questioned.[1] Also, it has been suggested that the output beam profile will inevitably show strong asymmetries at the short wavelength end of the tuning curve.[2] In this contribution, experimental results for the performance of hole coupling in terms of wavelength and bandwidth tunability, efficiency and beam profile as obtained at the FELIX facility will be presented.
[1] Modeling and operation of an edge-coupled free electron laser, M.D. Shin, TUOC3, FEL2010, Malmø [2] R. Prazeres et al, Phys. Rev. S.T. A/B, 13 (2010) 090702 |
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| WEPD41 | Construction and Commissioning of Coherent Light Source Experiment Station at UVSOR | 460 |
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| At UVSOR, Coherent light source technologies, such as resonator free electron laser, coherent harmonic generation and coherent synchrotron radiation via laser modulation, have been developed parasitically by using an undulator and a beam-line normally used for photo-electron spectroscopy. Under Quantum Beam Technology Program of MEXT in Japan, we started constructing a new experiment station dedicated for the coherent light source developments. We created a new straight section by moving the injection line. Two identical undulators 1m long were constructed and installed there. A buncher magnet was constructed and installed between the undulators to form an optical klystron. Two beam-lines, BL1U and BL1B, were constructed, the former of which is for free electron laser and coherent harmonic generation and the later for the coherent synchrotron radiation in the terahertz range. The laser system was reinforced and new laser transport line was constructed. The generation of coherent synchrotron radiation by laser modulation was already tested. The construction of the optical cavity for the free electron laser will start in this year. | ||
| WEPD42 | Electron Beam Dynamics in the ALICE IR-FEL Facility | 464 |
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| The ALICE facility at Daresbury Laboratory is an energy recovery test accelerator which includes an infra-red oscillator-type free electron laser (IR-FEL). The longitudinal phase space of the electron bunches and the longitudinal transport functions in the ALICE accelerator are studied in this paper. | ||
| WEPD44 | FEL Research and Development at STFC Daresbury Laboratory | 468 |
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| In this paper we present an overview of current and proposed FEL developments at STFC Daresbury Laboratory in the UK. We discuss progress on the ALICE IR-FEL since first lasing in October 2010, covering the optimisation of the FEL performance, progress on the demonstration of a single shot cross correlation experiment and the results obtained so far with a Scanning Near-Field Optical Microscopy beamline. We discuss a proposal for a 250 MeV single pass FEL test facility named CLARA to be built at Daresbury and dedicated to research for future light source applications. Finally we present a brief overview of other recent research highlights. | ||
| WEPD46 | Pulse Structure Measurement of Near-Infrared FEL in Burst-Mode Operation of LEBRA Linac | 472 |
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| The near-infrared free electron laser (FEL) at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been provided for scientific studies in various fields since 2003. Improvement in the electron beam injector system for the LEBRA 125MeV electron linac made possible to accelerate the electron beam in three different modes, full-bunch mode, superimpose mode and burst mode. FEL lasing in the second and the third modes was achieved in 2011. The FEL pulse lengths in the full-bunch mode and the burst mode, measured at an FEL wavelength of 1600 nm with autocorrelation method using a Michelson interferometer, were approximately 100 fs and 180 fs, respectively. The FEL gain in the burst mode was apparently much higher than that in the full-bunch mode. Although the autocorrelation method provides only a rough estimate, the burst-mode FEL pulse structure was suggested to be different from the full bunch mode. | ||
| WEPD47 | Development of Free-electron Lasers using Two "Higher Orders" with the Storage Ring NIJI-IV | 476 |
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Funding: This work was supported by the Budget for Nuclear Research of the Ministry of Education, Culture, Sports, Science and Technology of Japan. In National Institute of Advanced Industrial Science and Technology (AIST), higher harmonic oscillations of free-electron lasers (FELs) have been developed with the storage ring NIJI-IV*. We have already achieved the seventh harmonic FEL at a wavelength of around 890 nm, which is the highest order in the harmonic FELs**. Using another "higher order", that is, higher diffraction orders of a target wavelength of dielectric multilayer mirrors, we realized the following results: + shortening a wavelength of the FEL oscillation in the NIJI-IV IR-FEL system, + lasing on the highest order in the harmonic FEL, + discovering differences between the fundamental harmonic FEL and higher harmonic FEL, + controlling the harmonic order in the same condition of the electron beam and insertion device. In the presentation, we will report the characteristics of the FEL oscillations using the two higher orders in the NIJI-IV IR-FEL system. E-mail address: sei.n@aist.go.jp * N. Sei et al., J. Phys. Soc. Jpn., 79 (2010) 093501. ** N. Sei et al., Opt. Express, 20 (2012) 308. |
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| WEPD48 | Development of Intense Terahertz-wave Coherent Synchrotron Radiations at LEBRA | 480 |
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Funding: This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research 2365696. Nihon University and AIST have jointly developed intense terahertz-wave coherent synchrotron radiations at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. Because a bunch length is short and a charge is large in an electron beam of a linac to saturate free-electron laser (FEL) power, the electron beam of the linac in an FEL facility is suitable for generating intense coherent radiations generally. Therefore, we launched a development of a THz-wave source with using an upstream bending magnet located in the FEL beam line. Recently, Nihon University developed 'burst mode operation', in which two or three electron bunches were included at an interval of 22.4 or 44.8 ns [1]. The electric charge in the micropulse was high (several hundreds pC) in the burst mode, so generation and observation of the coherent synchrotron radiation became easy. We have already measured the intense THz-wave from LEBRA and confirmed it to be the coherent synchrotron radiation (CSR). It was also found that CSR might have serious influence on a high-energy electron beam. In the presentation, we will report the characteristics of the CSR at LEBRA. E-mail address: sei.n@aist.go.jp 1. K. Nakao et al., Lasing of near infrared FEL with the burst-mode beam at LEBRA, Proceedings of FEL11, Shanghai, China, (2011). |
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| WEPD49 | The Terahertz FEL Facility Project at CAEP | 484 |
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| To meet the requirement of material and biomedicine study, a terahertz FEL user facility project was proposed by China Academy of Engineering Physics(CAEP), at present the project has been approved and the facility will be constructed within 5 years. The facility will operate in the quasi CW mode and the average power is about 10W. The wavelength of the light can be regulated between 100μm/3THz to 300μm/1THz according to the user necessary by changing the electron energy and the magnetic field of the wiggler. In order to achieve the high brightness beam, the photocathode DC gun will be used as the electron source. The electron energy after a superconducting accelerator is about 8MeV, which is suitable to obtain the terahertz light. The facility will be a useful tool to the science. | ||
| WEPD51 | The parameter study of terahertz Free-Electron Laser Oscillator based on Electrostatic Accelerator | 488 |
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| Free-Electron Laser Oscillator based on Electrostatic Accelerator (EA-FELO) is one of the best methods to realize the powerful terahertz source, which can not only produce high power, but also obtain coherent and tunable wavelength. In this paper, we investigate the effects of the main parameters in this scheme, including the initial electron-beam energy spread, emittance and beam current. Besides, the influence of the radius of the mirrors and the position of the undulator on FEL performance is also studied. The numerical results from 1D FEL Oscillator simulation code FELO are presented, and show that this compact device could achieve the terahertz light with the peak output power is about 5.3kW. | ||
| WEPD52 | THz Radiation Sources based on RF-linac at Chiang Mai University | 492 |
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| A THz radiation source in a form of coherent radiation from short electron bunches has been constructed at the Plasma and Beam Physics (PBP) research facility, Chiang Mai University. The accelerator system consists of an RF-gun with a thermionic cathode, an alpha-magnet as a magnetic bunch compressor, and a SLAC-type linear accelerator. Coherent transition radiation emitted from short electron bunches passing through an Al-vacuum interface was used as the THz radiation source. This THz radiation can be used as a source of the THz imaging system and THz spectroscopy. Details of the accelerator system and THz radiation production will be presented. A plan for extension to accommodate Free Electron Lasers (FEL) optimized for mid-infrared and far-infrared/THz radiation will also be discussed. | ||
| WEPD53 | Linac-based THz Imaging at Chiang Mai University | 496 |
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Funding: the Thailand Center of Excellence in Physics (ThEP), the National Research Council of Thailand (NRCT) and the Thailand Research Fund (TRF) At the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University, intense THz radiation is generated in a form of coherent transition radiation from femtosecond electron bunches. The THz radiation is used as a source of THz imaging system which was successfully setup and tested. The radiation is focused onto a sample which will be scanned using an xy-translation stage. The transmission or reflection at different points of the sample are recorded to construct a THz image. Details of the setup and the experimental results from the system will be presented. The THz imaging to accommodate a future IR-THz Free Electron Laser (FEL) will also be discussed. |
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| WEPD54 | Characterization of Single-cycle THz Pulses at the CTR Source at FLASH | 500 |
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| At the coherent transition radiation source at the free-electron laser in Hamburg (FLASH) at DESY, single-cycle THz pulses with electric field strengths exceeding one MV/cm are generated. We present the temporal and spatial characterization of this source with the technique of electro-optic sampling using a laser system synchronized with the accelerator to better than 100 fs. This method offers a quantitative detection of the electric field of the THz pulses in the time domain. Compared to other electron-accelerator driven sources like undulator radiation, the transition radiation source provides pulses with a high bandwidth and durations shorter than one picosecond. This enables time-resolving and non-destructive experiments with radiation in the THz regime including THz pump / THz probe experiments. Broadband and intense THz pulses are expected to be valuable tools for the study of dynamics of excitation of complex materials in transient electric and magnetic fields. | ||
| WEPD55 | Tunable IR/THz Source for Pump Probe Experiments at the European XFEL | 503 |
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| We present a concept of an accelerator based source of powerful, coherent THz radiation for pump-probe experiments at the European XFEL. The electron accelerator is similar to that operating at the PITZ facility. It consists of rf gun and warm accelerating section (energy up to 30 MeV). The radiation is generated in a 5 meter long APPLE-type undulator with a period length of 4 cm, thus providing polarization control. Radiation with wavelength below 200 micrometers is generated using the mechanism of SASE FEL. Powerful coherent radiation with wavelength above 200 micrometers is generated in the undulator by a tailored (compressed) electron beam. Properties of the radiation are: wavelength range is 10 to 1000 micrometers (30 THz - 0.3 THz), radiation pulse energy is up to a few hundreds microjoles, peak power is 10 to 100 MW, spectrum bandwidth is 2 - 3%. It is important to note that the time structure of the THZ source ideally matches with the time structure of the x-ray pulses since the THZ source is based on the same technology as the injector of the European XFEL. A similar scheme can be also realized at LCLS, SACLA, or SWISS FEL with S-band rf accelerator technology. | ||
| WEPD58 | Emission of Coherent T-rays from Trains of Ultrashort Electron Pulses in a Pulsed Helical Undulator | 507 |
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| Sub-100 fsec electron pulses are produced from the 30 MeV NSRRC thermionic rf gun injector by beam selection in the alpha magnet as well as velocity bunching in the rf linac. The coherent infrared radiation from a pulsed helical undulator driven by such high rep.-rate electron beam being investigated theoretically. Recent progress of the installation of the injector will also be presented. | ||
| WEPD59 | FLUTE, a Compact Accelerator-based Source for Coherent THz Radiation | 511 |
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| FLUTE is a test facility for a compact accelerator-based THz source in the final design phase at the Karlsruhe Institute of Technology (KIT) in cooperation with Paul Scherrer Institute (PSI), Switzerland. The design is based on a 7 MeV photo injector, an S-band linac with a maximum energy of 50 MeV and a bunch compressor. The machine will be operated in a wide range of bunch charges, from 10 pC up to 3 nC. The final bunch length after the compressor is dominated by space charge effect in the photo injector and the coherent synchrotron radiation (CSR) in the compressor. This paper gives an overview over the status of the project and presents results of simulations for the different operating regimes. In addition, THz spectra generated by different processes (CSR, coherent transition radiation and coherent edge radiation) for different, charge dependent, bunch shapes will be discussed. | ||
| WEPD64 | FEL Gain Measurement with a Novel Method | 515 |
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| The FEL gain is an important factor characterizing performance of the FEL. We used to derive the gain of the THz-FEL at Osaka University from the macropulse shape measured using a Ge:Ga detector with the time resolution of ~10 ns. The method was recently found faulty because the response of the detector shows strong non-linearity in amplitude at a high intensity level. We, therefore, have developed a new method for the gain measurement using a silicon bolometer, which has a very high linearity over the wide intensity range. The detector has the time resolution of ~1 ms, which is much longer than the FEL macropulse of a few microseconds, so that it measures energy in the macropluse. In order to derive the temporal revolution of FEL power, the number of amplifications is varied by changing the macropulse length of the electron beam. The sensitivity of the detector is also high, so that we could measure the energy development of the FEL over 6~7 orders of magnitude at a wavelength ~100 micrometers in combination with appropriate absorbers. We will report results of the measurement and analysis of the FEL gain. | ||
| WEPD65 | Design and Numerical Simulation of THz-FEL Amplifier in Kyoto University | 519 |
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| Design of a compact and economic THz free-electron laser (FEL) amplifier, which consists of a BNL-type 1.6 cells photocathode radio frequency gun, Solenoid, transport line and short undulator, has been studied at Kyoto University. The electron beam energy to obtain FEL with a wavelength of the range 150~400 μm was calculated to be 4.1~7.0 MeV for a bunch charge of 1.0 nC/bunch. The numerical calculations of the electron beam from the RF gun up to the undulator entrance are carried out using Parmela code and the FEL properties from the undulator will be simulated using GENESIS 1.3. The expected FEL spectral was estimated using 4~5 undulator periods with ~30 cm length and 0.3 T magnetic field. Details of the design concept, numerical calculations and results will be presented in the conference. | ||
| WEPD66 | Phase Space Manipulation with Laser-generated Terahertz Pulses | 523 |
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| Ultrafast lasers are able to generate THz pulses with >1MV/m field strengths, and with controllable electric field temporal profiles. We report on an experiment to demonstrate the use of laser generated THz pulses to manipulate the γ-z correlation of a ∼ 20MeV electron bunch on a sub picosecond time scale. The manipulation is achieved in free space, without external magnetic fields or undulators, by the interaction of the bunch with the longitudinal electric field of a co-propagating THz pulse in a TEM10*-like mode. We discuss the potential for arbitrary phase space control, including the possibility of correcting temporal jitter and driving electron beams into synchronisation with the laser. | ||
| WEPD68 | UCLA Seeded THz FEL Undulator Buncher Design | 527 |
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UCLA is planning to build a THz user facility. One is a seeded THz FEL tunable in the range of 0.5 - 3 THz or even 3-9 THz in an optical klystron configuration. Another* relies on microbunching at 340 micron using a 3.3 cm undulator or even driving the FEL with an electron beam from a laser-plasma accelerator. These FEL's make use of a 2.1m long pre-buncher, chicane and shorter, 110cm long radiator. Chicane requirements are modest. A round copper waveguide with 4.8mm ID will be used. We will describe the magnetic design and measured performance of the gap tunable undulators, mechanical design of the entire system, vacuum boxes, waveguides and expected operational approaches. Both undulators have 33mm periods and curved poles for two-plane focusing. Discussions will be included on issues associated with fabricating, sorting and shimming curved pole undulators. A new optimization method will be described that was used to meet magnetic requirements with a minimum volume of magnetic material.
*S. Tochitsky et al, "Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory", Advanced Accelerator Conference 2010 |
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