Paper | Title | Other Keywords | Page |
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MOICNO01 | Generation of a Train of Short Pulses by Means of FEL Emission of a Combed Electron Beam | electron, FEL, undulator, laser | 2 |
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We present a direct and powerful method for generating train of radiation pulses based on the FEL radiation from a multi-peaked electron beam produced with a combed laser pulse accelerated and compressed in a linac by the velocity bunching technique. The electron beam, constituted by two bunches, can be extracted from the accelerating section when they are temporaly superimposed but separated in energy, so that each of them is characterized by a different value of the Lorentz factor. When driven in the FEL undulator, they emit two separate spectral lines, according to the FEL resonance condition, that interfere producing fringes in the time-domain. In this way a train of regular pulses can be obtained, without limitation in frequency, and with the perspective of reaching the attosecond domain in the X ray regime. | |||
Slides MOICNO01 [8.836 MB] | |||
MOOCNO04 | Using a Lienard-Wiechert Solver to Study Coherent Synchrotron Radiation Effects | simulation, undulator, electron, dipole | 17 |
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We report on coherent synchrotron radiation (CSR) modeling using a new first-principles Lienard-Wiechert solver (CSR3D) that simulates real-world number of particles (624 million to 6.24 billion for 100-pC to 1-nC bunch charges). Using this tool, we have verified the limits of applicability of the common 1-D CSR model, including effect due to transverse beam size and shape. We also have observed energy dependent, wavelength dependent, and transverse-size dependent effects on CSR enhancement from microbunching. Additionally, we describe statistics of CSR shot noise, including dependencies on beam energy and transverse position and resulting energy diffusion. We consider the full transverse equation of motion and also quantify the effect of emittance growth from the bunch’s transverse radiation force. | |||
Slides MOOCNO04 [6.258 MB] | |||
MOPSO04 | Theoretical Analysis of a Laser Undulator-Based High Gain FEL | laser, FEL, undulator, electron | 27 |
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The use of laser (or RF) undulators is nowadays considered attractive for FEL applications, particularly those that aim to utilize relatively low-energy electron beams. In the context of the standard theoretical analysis, the counter-propagating laser pulse is usually treated in the plane-wave approximation, neglecting amplitude and phase variation. In this paper, we develop a three-dimensional, analytical theory of a high-gain FEL based on a laser or RF undulator, taking into account the longitudinal variation of the undulator field amplitude, the laser Gouy phase and the effects of emittance and energy spread in the electron beam. Working in the framework of the Vlasov-Maxwell formalism, we derive a self-consistent equation for the radiation amplitude in the linear regime, which is then solved to good approximation by means of an orthogonal expansion technique [*]. Numerical results obtained from our analysis are used in the study of an example of a compact, laser undulator-based, X-ray FEL.
*P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013). |
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MOPSO06 | Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method | impedance, vacuum, simulation, synchrotron | 32 |
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Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico. We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study. * See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2. ** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012). |
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MOPSO07 | Channeling Radiation With Low-Energy Electron Beams: Experimental Plans and Status at Fermilab | electron, emittance, brilliance, laser | 38 |
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Funding: This work was supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 with Vanderbilt University and Northern Illinois University. Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams. In this contribution we describe the anticipated performance and preliminary results from a channeling radiation experiment to produce ~ 1.2-keV radiation from a ~ 4-MeV electron beam at Fermilab's high-brightness electron source lab(HBESL). We also discuss plans to produce X-ray radiation ([10,80]-keV photon energy) at Fermilab's advanced superconducting test accelerator (ASTA). |
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MOPSO08 | Unaveraged Modelling of a LWFA Driven FEL | FEL, simulation, electron, undulator | 43 |
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Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed.
[1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012) |
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MOPSO09 | Investigation of a 2-Colour Undulator FEL Using Puffin | undulator, FEL, electron, bunching | 47 |
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The unaveraged FEL code Puffin* is used to investigate a 2 color FEL. In the scheme under investigation, undulator modules are tuned alternately to generate 2 frequencies quasi-simultaneously, which should result in greater stability than generating them consecutively. The advantage of using Puffin is that it provides the capability of modelling a broad bandwidth spectrum. For example, radiation at 1nm and 2.4nm is difficult to model simultaneously in standard averaged FEL codes. An unaveraged code like Puffin is able to model 2 (or more) wavelengths with a much wider spacing.
* LT Campbell and BWJ McNeil, Phys. Plasmas 19, 093119 (2012) |
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MOPSO27 | Study of CSR Effects in the Jefferson Laboratory FEL Driver | FEL, simulation, dipole, linac | 58 |
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Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work also received supported under U.S. DOE Contract No. DE-AC05-06OR23177. In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped. |
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MOPSO30 | Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation | undulator, electron, laser, FEL | 63 |
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Funding: Work supported by Hungarian Research Fund (OTKA), grant number 101846, and from SROP-4.2.1.B-10/2/KONV-2010-0002 and SROP-4.2.2/B-10/1-2010-0029 Robust methods for producing waveform-controlled half-cycle–few-cycle pulses in the mid-infrared (MIR)–extreme ultraviolet (EUV) spectral range are proposed. They are based on coherent Thomson scattering of THz pulses on relativistic ultrathin electron layers and coherent undulator radiation of relativistic ultrathin electron layers, respectively. The ultrathin electron layers are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers if a single-period modulator undulator with period length significantly shorter than the resonant one is used and the undulator parameter is only K=0.25. Thomson scattering of THz pulses on ultrathin electron layers with only 50 MeV energy can generate for example 170 as long single-cycle pulses at 80 nm wavelength with 0.1 nJ energy. Coherent undulator radiation of ultrathin electron layers with 450 MeV energy can generate single-cycle radiation in the 20 nm – 1000 nm wavelength range. The corresponding pulse energy and pulse duration vary in the 10 pJ – 2 nJ and 47 as – 2.1 fs ranges, respectively. |
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MOPSO31 | Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave | resonance, undulator, FEL, electron | 762 |
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Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY. We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds. * J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph] |
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MOPSO60 | Channeled Positrons as a Source of Gamma Radiation | positron, electron, photon, ion | 101 |
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Funding: ISTC A possibility of channeling of low-energy (5 / 20Mev) relativistic positrons with coaxial symmetry around separate crystal axes of negative ions in some types of crystals, is shown. The annihilation processes of positrons with medium electrons are investigated in details. The lifetime of a positron in the regime of channeling is estimated 〖10〗-6 sec which on a 〖10〗9/〖10〗8 times is bigger than at usual cases. |
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MOPSO61 | Modulated Medium for Generation of Transition Radiation | electron, dipole, lattice, polarization | 105 |
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Funding: ISTC It is shown on an example of amorphous quartz, under the influence of a standing microwave field, at its certain parameters, superlattice is created in the medium where difference in values of dielectric constants of neighboring layers can be up to third order. This superlattice exists during the nanosecond, however it is sufficient for using it as a radiator for generation of transition radiation by relativistic electrons. |
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MOPSO66 | Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons | electron, simulation, FEL, emittance | 112 |
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Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation. |
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MOPSO70 | Crystal Channeling Acceleration Research for High Energy Linear Collider at ASTA Facility | acceleration, electron, plasma, laser | 122 |
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The density of charge carriers in solids is significantly higher than what was considered above in plasma, and correspondingly, the longitudinal fields of up to 10 TV/m are possible. It was suggested that particles are accelerated along major crystallographic directions, which provide a channeling effect in combination with low emittance determined by an Angstrom-scale aperture of the atomic “tubes.” However, the major challenge of this channeling acceleration is that ultimate acceleration gradients might require relativistic intensities at hard x-ray regime (~ 40 keV), exceeding those conceivable for x-rays as of today, though x-ray lasers can efficiently excite solid plasma and accelerate particles inside a crystal channel. However, the acceleration will take place only in a short time before full dissociation of the lattice. Carbon nanotubes have great potential with a wide range of flexibility and superior physical strength, which can be applied to channeling acceleration and possibly fast cooling. This talk will present past and current efforts on crystal acceleration research and discuss feasible experiments with the ASTA and beyond. | |||
MOPSO74 | Reevaluation of Coherent Electron Cooling Gain Factor | FEL, electron, undulator, hadron | 132 |
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In Ref. [1] the authors put forward a concept of coherent electron cooling of hadrons. At the core of the concept lies the following idea: a density perturbation induced by an hadron in a co-propagating relativistic electron beam is amplified by several orders of magnitude in a free electron laser (FEL). After the FEL the electron beam is merged again with the hadron one and the amplified electric field in the electron beam acts back on each hadron resulting, after many repetitions, in cooling of the hadron beam. The efficiency of the process is critically determined by the amplification factor of the longitudinal electric field induced by the hadron in the electron beam. In this work we show that this factor is actually considerably smaller than the (conventionally defined) FEL gain with the smallness parameter to be the relative bandwidth of the FEL amplifier.
[1] V. N. Litvinenko and Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009). |
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TUOBNO01 | Beam Diagnostics for Coherent Optical Radiation Induced by the Microbunching Instability | gun, linac, laser, diagnostics | 169 |
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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). |
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Slides TUOBNO01 [1.805 MB] | |||
TUPSO27 | Design for a Fast, XFEL-Quality Wire Scanner | photon, vacuum, electron, instrumentation | 276 |
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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. | |||
TUPSO41 | The Ultrashort Beam Linac System and Proposed Coherent THz Radiation Sources at NSRRC | electron, linac, gun, undulator | 309 |
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The NSRRC ultrashort beam facility is a low energy linac system which is being built to produce femtosecond electron beam for novel light source development. Experiments on prebunched THz FEL and inverse Compton scattering x-ray source are under study. The electron source is a 2998 MHz, 1.5-cell thermionic rf gun with uneven full-cell to half-cell field ratio that is optimized to produce a energy-chirped electron beam. With movable slits in its vacuum vessel, the alpha magnet system is served also as a beam selector. Further bunch compression is done by velocity bunching in the rf linac. Recent progress of the construction of this facility as well as the design study of a prebunched THz FEL with this ultrashort electron beam will be reported. | |||
TUPSO45 | Initial Streak Camera Measurements of the S-band Linac Beam for the University of Hawaii FEL Oscillator | FEL, electron, linac, undulator | 325 |
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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. |
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TUPSO52 | R&D Towards a Delta-type Undulator for the LCLS | undulator, vacuum, polarization, FEL | 348 |
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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. | |||
TUPSO62 | Status of the Planar Undulator Applied in HUST THz-FEL Oscillator | undulator, FEL, electron, focusing | 372 |
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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. | |||
TUPSO64 | Short SASE-FEL Pulses at FLASH | laser, FEL, electron, free-electron-laser | 379 |
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Funding: This project has been supported by BMBF under contract 05K10GU2 & FS FLASH 301 FLASH is a high-gain free-electron laser (FEL) in the soft x-ray range. This paper discusses the production of very short FEL pulses in the SASE-mode without an external seeding signal at FLASH in the optimal case the single-spike operation. A new photo-injector laser has been commissioned, which allows the generation of shorter bunches with low bunch charge directly at the photo-cathode. This shorter injector laser reduces the required bunch compression for short pulses and thus allows a stable SASE performance with shorter pulses. First SASE performance using the new injector laser has been demonstrated and electron bunch and FEL radiation properties have been measured. Beam dynamics as well as the optimization of bunch diagnostics for low charge and short bunches are discussed. |
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TUPSO66 | Transport of Terahertz-Wave Coherent Synchrotron Radiation With a Free-electron Laser Beamline at LEBRA | FEL, electron, undulator, linac | 383 |
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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 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. |
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TUPSO77 | Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field | undulator, electron, focusing, simulation | 406 |
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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 | FEL, photon, diagnostics, electron | 417 |
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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 | laser, controls, photon, FEL | 438 |
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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. | |||
WEIANO01 | Towards Zeptosecond-scale Pulses From X-ray Free Electron Lasers | electron, FEL, undulator, laser | 458 |
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The short wavelength and high peak power of the present generation of Free-Electron Lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (~10-100 attosecond) capabilities of other light sources – but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (<~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a proposed method [1] to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications.
[1] D.J. Dunning, B.W.J. McNeil, N.R. Thompson, Phys. Rev. Lett. 110, 104801 (2013). |
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Slides WEIANO01 [3.492 MB] | |||
WEOANO03 | Longitudinal Coherence in an FEL With a Reduced Level of Shot Noise | FEL, electron, laser, undulator | 469 |
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For a planar free electron laser (FEL) configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches [1]. We calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses and the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. We also propose a scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.
V.A. Goryashko and V. Ziemann, Phys. Rev. ST Accel. Beams 16, 030702 (2013). |
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Slides WEOANO03 [1.999 MB] | |||
WEOBNO03 | Intense Emission of Smith-Purcell Radiation at the Fundamental Frequency from a Grating Equipped with Sidewalls | simulation, electron, bunching, solenoid | 477 |
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The two-dimensional theory of the Smith-Purcell free-electron laser predicts that coherent Smith-Purcell radiation can occur only at harmonics of the frequency of the evanescent wave that is resonant with the beam. Particle-in-cell simulations have shown that in a three-dimensional context, where the lamellar grating has sidewalls, coherent Smith-Purcell radiation can be copiously emitted at the fundamental frequency, for a well-defined range of beam energy. An experiment at microwave frequencies has confirmed this prediction . The power output is considerably greater than for the previously observed emission at the second harmonic, in agreement with three-dimensional simulations . The dependence of frequency on beam energy and emission angle is in good agreement with three-dimensional theory and simulations. Provided that a reduction in scale can be achieved, a path is open to coherent Smith-Purcell radiation at Terahertz frequencies.
(1) J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012). (2) J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011). |
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Slides WEOBNO03 [11.891 MB] | |||
WEOCNO03 | 3-D Theory of a High Gain Free-Electron Laser Based on a Transverse Gradient Undulator | FEL, electron, undulator, emittance | 481 |
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The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a great reduction of the FEL gain, an effect which is relevant when one considers FELs driven by plasma accelerators or storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU) [*,**]. In this concept, the energy spread problem is mitigated by properly dispersing the e-beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based high gain FEL, taking into account three-dimensional (3-D) effects and beam size variations along the undulator [***]. The results of our theory compare favorably with simulation and are used in fast optimization studies of various X-ray FEL configurations.
*T. Smith et al., J. Appl. Phys. 50, 4580 (1979). **Z. Huang, Y. Ding, C. Schroeder, Phys. Rev. Lett. 109, 204801 (2012). ***P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013). |
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Slides WEOCNO03 [3.217 MB] | |||
WEPSO02 | Results and Perspectives on the FEL Seeding Activities at FLASH | laser, undulator, electron, FEL | 491 |
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In recent years, several methods of free-electron laser (FEL) seeding, such as high-gain harmonic generation (HGHG), self-seeding, or direct FEL amplification of external seed pulses, have proven to generate intense, highly coherent radiation pulses in the extreme ultraviolet (XUV), soft- (SXR) and hard (HXR) X-ray spectral range. At DESY in Hamburg, the FEL facility FLASH is currently being upgraded by a second undulator beamline (FLASH2) which allows for the implementation of various seeding schemes. The development of high repetition-rate, high-power laser systems allows for the production of seed sources which match the bunch-train pattern of FLASH. Furthermore, the FLASH1 beamline arrangement is well suited for testing various seeding schemes including HGHG, EEHG, HHG-seeding, and hybrid schemes. In this contribution, we* give an overview of latest results and planned FEL seeding activities at FLASH.
*Joern Boedewadt on behalf of the FLASH seeding collaboration (DESY, U Hamburg, TU Dortmund, U Uppsala, U Stockholm) |
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WEPSO06 | The Test-FEL at MAX-lab: Implementation of the HHG Source and First Results | laser, electron, FEL, undulator | 507 |
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The test-FEL at MAX-lab is a development set-up for seeding techniques. After the successful demonstration of coherent harmonic generation from a conventional laser, the new layout now presents a gas target for generation of harmonics. The drive laser will be up-converted and the low harmonics (around 100 nm) will seed the electron beam. The energy modulated electrons will then be bunched in the dispersive section and will radiate in the second undulator. We will detect the second harmonic of the HHG radiation around 50 nm. This experiment has several challenges never tried before: co-propagation of the electron beam and the drive laser, interaction of the electron beam with the gas in the target, no-focusing of the harmonics and no drive laser removal. The commissioning will show if this kind of in-line chamber has advantages with respect to more traditional approaches with optical beam transport. The results are relevant for many facilities that are planning to implement HHG seeding in the near future. | |||
WEPSO07 | Simulation Studies for an X-ray FEL Based on an Extension of the MAX IV Linac | FEL, linac, undulator, electron | 510 |
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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. | |||
WEPSO11 | Coherent X-Ray Seeding Source for Driving FELs | cavity, undulator, FEL, electron | 522 |
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Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options. |
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WEPSO14 | Towards High Frequency Operation with a Multi-Grating Smith-Purcell FEL | simulation, electron, FEL, bunching | 525 |
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Three-dimensional simulations and experiments have shown that, for a grating equipped with sidewalls, copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave is possible 1, 2. Since the underlying theory is scale invariant, the wavelength emitted is reduced in proportion to a uniform rescaling of the grating. In order to increase our 5 GHz to 100 GHz , the grating surface would be reduced by a factor of 400, which would lead to greatly reduced power. In addition, the required beam might be hard to generate. To avoid this, we propose to use several gratings in parallel with no overall reduction in the total width and the same beam as in our microwave experiment. For this scheme to succeed, it is essential that the bunching in the different gratings be coherent. . Simulations suggest that this occurs for as much as a ten-fold scale reduction. To test this idea, an experiment is using several gratings is being performed.
1. J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011). 2. J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012),. |
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WEPSO26 | Status of the Flash Facility | photon, FEL, electron, undulator | 550 |
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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. | |||
WEPSO34 | Proposal for a Scheme to Generate a 10 tw Power Level, Femtosecond X-ray Pulses for Bio-imaging of Single Protein Molecules at the European XFEL | undulator, photon, FEL, electron | 574 |
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Crucial parameters for bio-imaging experiments are photon energy range, peak power and pulse duration. For a fixed resolution, the largest diffraction signals are achieved at the longest wavelength supporting that resolution. In order to perform these experiments at the European XFEL, we propose to use a novel configuration combining self-seeding and undulator tapering techniques with the emittance-spoiler method. Experiments at the LCLS confirmed the feasibility of these three techniques. Their combination allows obtaining a dramatic increase the XFEL output peak power and a shortening of the photon pulse duration to levels sufficient for performing bio-imaging of single protein molecules at the optimal photon-energy range between 3 keV and 5 keV. We show here that it is possible to achieve up to a 100-fold increase in peak-power of the X-ray pulses at the European XFEL: the X-ray beam would be delivered in 10 fs-long pulses with 50 mJ energy each at a photon energy around 4 keV. We confirm by simulations that one can achieve diffraction before destruction with a resolution of 0.25 nm resolution. | |||
WEPSO41 | Feasibility Studies for Echo-enabled Harmonic Generation on CLARA | laser, bunching, electron, FEL | 588 |
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The Compact Linear Accelerator for Research and Applications (CLARA) is a proposed single-pass FEL test facility, designed to facilitate experimental studies of advanced FEL techniques applicable to the next generation of light source facilities. One such scheme under consideration is Echo-Enabled Harmonic Generation (EEHG). In this paper we explore the suitability of CLARA for carrying out studies of this scheme, combining analytical and numerical calculations to determine likely hardware operating ranges, parameters tolerances and estimated FEL performance. A possible adaptation to convert EEHG into a short-pulse scheme is also considered. | |||
WEPSO43 | EEHG and Femtoslicing at DELTA | electron, undulator, laser, synchrotron | 594 |
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The ultrashort-pulse facility at DELTA (a 1.5-GeV synchrotron light source operated by the TU Dortmund University) based on the coherent harmonic generation (CHG) technique will be upgraded using echo-enabled harmonic generation (EEHG) in order to reach shorter wavelengths. A laser-induced energy modulation is employed in the CHG and EEHG schemes to create a periodic electron density modulation, but can also be used to generate ultrashort pulses of incoherent radiation at arbitrary wavelengths by transversely displacing the off-energy electrons(femtoslicing). A new storage-ring lattice for DELTA will be presented that not only offers enough free straight sections for an EEHG and femtoslicing setup, but also allows to operate both radiation sources simultaneously. | |||
WEPSO44 | Design Studies for FLUTE, A Linac-based Source of Terahertz Radiation | laser, gun, simulation, linac | 598 |
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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. | |||
WEPSO47 | Simulation Results of Self-seeding Scheme in PAL-XFEL | undulator, electron, simulation, emittance | 606 |
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There are two major undulator lines in Pohang Accelerator Laboratory XFEL (PAL XFEL), soft X-ray and hard X-ray. For the hard X-ray undulator line, self-seeding is the most promising approach to supply narrow bandwidth radiation to the users. The electron energy at hard X-ray undulator is 10 GeV and the central wavelength is 0.1 nm. We plan to provide the self-seeding option in the Phase I operation of PAL-XFEL. In this talk, the simulation results for the self-seeding scheme of hard X-ray undulator line in PAL XFEL will be presented. | |||
WEPSO51 | Self-seeding Design for SwissFEL | FEL, undulator, simulation, electron | 618 |
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The SwissFEL facility, planned at the Paul Scherrer Institute, will provide SASE and self-seeded FEL radiation at a hard (1-7 Å) and soft (7-70 Å) X-ray FEL beamlines. This paper presents the current status of the self-seeding design for SwissFEL. The layout and full 6D start-to-end simulation results are presented for the hard X-ray beamline. Studies for different charges and optimization of the first and second undulator stages are shown. | |||
WEPSO53 | Harmonic Lasing at the LCLS | electron, FEL, undulator, simulation | 623 |
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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) |
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WEPSO57 | Optimization of a Dedicated Bio-imaging Beamline at the European X-ray Fel | undulator, electron, photon, FEL | 632 |
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We recently proposed a basic concept for design and layout of a dedicated undulator source for bio-imaging experiments at the European XFEL. Here we present an optimization of that concept. The core of the scheme is composed by soft and hard X-ray self-seeding setups. Using an improved design for both monochromators it is possible to increase the design electron energy up to 17.5 GeV in photon energy range between 2 keV and 13 keV, which is the most preferable for life science experiments. Operating at such high electron energy one increases the X-ray output peak power. Moreover, 17.5 GeV is the preferred operation energy for SASE1 and SASE2 users. This choice will reduce the interference with other undulator lines. We include a study of the performance of the self-seeding scheme accounting for spatiotemporal coupling caused by the use of a single crystal monochromator. This distortion can be easily suppressed by the right choice of diamond crystal planes. The proposed undulator source yields about the same performance as in the case for a X-ray seed pulse with no coupling. Simulations show that the FEL power reaches 2 TW in the 3 keV - 5 keV photon energy range. | |||
WEPSO58 | Status Report of the Short-pulse Facility at the Delta Storage Ring | laser, electron, synchrotron, klystron | 642 |
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Funding: * Work supported by DFG, BMBF and by the Federal State NRW. At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund university, a short-pulse facility employing the CHG (Coherent Harmonic Generation) principle is in operation. Here, the interaction of an intense, ultrashort laser pulse and electrons in an undulator leads to microbunching of a small fraction of the electrons in the bunch. As a consequence, ultrashort, coherent synchrotron-radiation pulses in the VUV regime are emitted at harmonics of the incident laser wavelength. In addition, coherent THz pulses on the sub-ps timescale are generated. In this paper, the latest improvements of the facility and recent measurements are presented, including investigation of the transverse coherence and detection of the CHG radiation using photoemission spectroscopy in a VUV beamline. |
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WEPSO59 | A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm | undulator, FEL, electron, simulation | 646 |
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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 | undulator, FEL, bunching, polarization | 651 |
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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. | |||
WEPSO63 | Extension of SASE Bandwidth up to 2 % as a Way to Increase Number of Indexed Images for Protein Structure Determination by Femtosecond X-Ray Nanocrystallography at the European XFEL | electron, undulator, simulation, photon | 661 |
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Experiments at the LCLS confirmed the feasibility of femtosecond nanocrystallography for protein structure determination at near-atomic resolution. These experiments rely on X-ray SASE pulses with a few microradians angular spread, and about 0.2 % bandwidth. By indexing individual patterns and then summing all counts in all partial reflections for each index it is possible to extract the square modulus of the structure factor. The number of indexed images and the SASE bandwidth are linked, as an increasing number of Bragg spots per individual image requires an increasing spectral bandwidth. This calls for a few percent SASE bandwidth. Based on start-to-end simulations of the European XFEL baseline, we demonstrate that it is possible to achieve up to a 10-fold increase of the electron energy chirp by strongly compressing a 0.25 nC electron bunch. This allows for data collection with a 2 % SASE bandwidth, a few mJ radiation pulse energy and a few fs-pulse duration, which would increase the efficiency of protein determination at the European XFEL. We prove this concept with simulations of photosystem-I nanocrystals, with a size of about 300 nm. | |||
WEPSO65 | LEBRA Free Electron Laser as a Radiation Source for Photochemical Reactions in Living Organisms | FEL, electron, controls, laser | 675 |
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The radiation sources commonly used in plant applications are commercially available lamps developed for human lighting applications (fluorescent, metal halide, high-pressure sodium, incandescent, light-emitting diode, and laser diode). In contrast, free-electron lasers (FELs) such as LEBRA-FEL produce high-energy, tunable pulse radiation and thus are promising radiation sources for photochemical research. An advantage of LEBRA-FEL is that the peak intensity ranges from 0.35 to 6.5 microns which are wavelengths coinciding with the absorption peaks of living organisms. Previously, we established a microscopic irradiation technique for delivering visible FEL light to single cells through a tapered glass rod (< 10 microns). However, it is still unclear whether LEBRA-FEL can produce sufficient radiant energy at wavelengths effective for triggering photochemical reactions in living organisms. The aim of this study was to evaluate the effectiveness of LEBRA-FEL in lettuce-seed germination tests. Results show promotion by red light and inhibition by far-red light, indicating that LEBRA-FEL can be used to control lettuce-seed germination. | |||
WEPSO69 | Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide | coupling, FEL, cavity, undulator | 689 |
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Funding: the Fundamental Research Funds for the Central Universities,HUST:2012QN080 The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized. |
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WEPSO80 | Coherence Properties of the Radiation From FLASH | emittance, FEL, undulator, electron | 704 |
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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. | |||
WEPSO89 | Design of a Resonator for the CSU THz FEL | FEL, higher-order-mode, coupling, undulator | 719 |
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Funding: This research is support by Office of Naval Research Global, grant number N62909-10-1-7151 A 6-MeV L-band linac will be used to drive a planar, fixed gap, 2.5-cm period, hybrid undulator with parabolic pole faces. Consequently, this system is capable of generating wavelengths from 160 to 600 μm. In this paper we discuss the design of an optical resonator for this system. The resonator uses hole-coupled mirrors to allow for a straight electron beam line. The Rayleigh length, the position of the waist of the cold-cavity mode and the hole radii will be investigated to optimize the performance of the FEL. |
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THOBNO01 | Three Unique FEL Designs for the Next Generation Light Source | FEL, undulator, photon, laser | 734 |
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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 THOBNO01 [1.331 MB] | |||