Keyword: radiation
Paper Title Other Keywords Page
MOB01 Pulse Control in a Free Electron Laser Amplifier FEL, electron, laser, undulator 9
 
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  
  Funding: Work supported by MIUR (DM1834 RIC.4-12-2002 and Grants No. FIRB- RBAP045JF2 and No. FIRB-RBAP06AWK3), and by the EU Commission in the Sixth Framework Program, Contract No. 011935- EUROFEL.
A significant progress has been made in controlling the properties of the radiation emitted by a FEL amplifier. Experiments have demonstrated the possibility both to increase the temporal coherence and to reduce the amplifier length to reach saturation, by seeding it with an external source. This may be a solid state, short pulse, laser (Ti:Sa,OPA..), doubled or tripled in a crystal, or a high order harmonic pulse generated in gas. The coherence improvement and the increased compactness of the source are only the first beneficial offspring of this marriage between the optical laser world and that of FELs. Non-linear effects in the seeded FEL dynamics may be exploited to shorten the pulse length beyond that allowed by the FEL natural gain bandwidth. Multiple seed pulses can be used to generate pulses whose temporal distance and properties are also controlled. Similarly, the FEL gain can be adapted to match the seed properties by tailoring the electrons phase space to generate ultra-short output pulses at unparalleled intensities. I had the honor (and luck) to participate in many relevant experiments at the SPARC and FERMI FELs and I will give my personal overview. 		 
slides icon Slides MOB01 [29.932 MB]  
 
MOB03 Phase Space Manipulations in Modern Accelerators laser, electron, FEL, cavity 16
 
  • D. Xiang
    Shanghai Jiao Tong University, Shanghai, People's Republic of China
  
  Funding: This work was supported by the National Natural Science Foundation of China under Grants No. 11327902.
Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities. 		 
slides icon Slides MOB03 [5.078 MB]  
 
MOP001 Particle Tracking Simulations for EXFEL Complex shape Collimators electron, simulation, lattice, photon 22
 
  • V.G. Khachatryan, V.H. Petrosyan, T.L. Vardanyan
    CANDLE SRI, Yerevan, Armenia
  
  The study sets the objective to investigate through numerical simulation the produced secondary radiation properties when the electron beam particles hit collimator walls. Using particle tracking simulation code FLUKA, the European XFEL electron beam as well as beam halo interaction with the collimator were simulated. The complex geometrical shape and material composition of the collimator have been taken into account. Absorbed dose spatial distribution in the material of the collimators and particle fluencies from the downstream surface of the collimator were simulated for the total secondary radiation and its main components.  
 
MOP003 Helical Undulator Radiation in Internally Coated Metallic Pipe vacuum, undulator, synchrotron-radiation, impedance 26
 
  • T.L. Vardanyan, A. Grigoryan, L.V. Hovakimyan, M. Ivanyan, A.V. Tsakanian, V.M. Tsakanov
    CANDLE SRI, Yerevan, Armenia
  
  The vacuum chambers of many advanced undulator sources are coated internally in order to reduce the impedance of the vacuum chamber or improve the vacuum performance. Although the impedances and radiation properties of the internally coated metallic pipes for straightforward moving charge are well studied, the peculiarities of the particles wiggling motion on the radiation characteristics in such structure are missed. In this paper we obtain exact expressions for the fields of a particle moving along a spiral path, as in the single-layer resistive as well as in the two-layer metallic waveguides, modelling NEG coating of the waveguide walls. Based on these results, it will be possible to obtain the necessary characteristics of the radiation of helical undulators, very close to reality. The solution is obtained as a superposition of a particular solution of inhomogeneous Maxwell's equations in a waveguide with perfectly conducting walls, and the solutions of the homogeneous Maxwell equations in the single-layer and double-layer resistive waveguides. Solution in the form of the multipole expansion for inhomogeneous Maxwell's equations for a waveguide with perfectly conducting walls, are also obtained in this study.  
 
MOP010 The Photon Beam Loss Monitors as a Part of Equipment Protection System at European XFEL photon, detector, vacuum, beam-transport 37
 
  • N. Gerasimova, H. Sinn
    XFEL. EU, Hamburg, Germany
  • S. Dziarzhytski, R. Treusch
    DESY, Hamburg, Germany
  
  For the X-ray beam transport systems, the problem of potential damage to the equipment by mis-steered photon beam emerged with advent of powerful X-ray FELs. In particular high repetition rate machines as European XFEL, where not only focused beam can produce ablation, but even unfocused beam can melt the beamline components while machine operates in multibunch mode, demand for implementation of equipment protection. Here we report on development of photon beam loss monitors at European XFEL facility. The photon beam loss monitors will react on the mis-steered photon beam and interface the machine protection system. The prototype comprises the vacuum chamber with fluorescence crystals positioned outside the photon beampath. The fast sub-hundred ns fluorescence induced by mis-steered beam can be detected by photomultiplier tube allowing for intra-train reaction of machine protection system. First tests have been carried out at FLASH and shown the feasibility of detection based on PMT-detected fluorescence. In addition to efficient YAG:Ce crystal, the robust low-Z material as CVD microcrystalline diamonds has shown a potential to be used as fluorescence crystals.  
 
MOP017 Measurement of the Output Power in Millimeter Wave Free Electron Laser using the Electro Optic Sampling Method laser, FEL, detector, electron 50
 
  • A. Klein
    Israeli Free Electron Laser, Ariel, Israel
  • A. Abramovich
    Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
  • D. Borodin, A. Friedman
    Ariel University, Ariel, Israel
  • H. S. Marks
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  
  Funding: this work funded in part by Israel Minstry of Defence
In this experimental work an electro optic (EO) sampling method was demonstrated as a method to measure the output power of an Electrostatic Accelerator Free Electron Laser (EA-FEL). This 1.4 MeV EA-FEL was designed to operate at the millimeter wavelengths and it utilizes a corrugated waveguide and two Talbot effect quasi-optical reflectors with internal losses of ~30%. Millimeter wave radiation pulses of 10 μs at a frequency of about 100 GHz with peak power values of 1-2 kW were measured using conventional methods with an RF diode. Here we show the employment of an electro-optic sampling method using a ZnTe nonlinear crystal. A special quasi optical design directs the EA-FEL power towards the ZnTe nonlinear crystal, placed in the middle of a cross polarized configuration, coaxially with a polarized HeNe laser beam. The differences in the ZnTe optical axis due to the EA-FEL power affects the power levels of the HeNe laser transmission. This was measured using a polarizer and a balanced amplifier detector. We succeeded in obtaining a signal which corresponds to the theoretical calculation. 		 
 
MOP019 Double-grating Monochromator for Ultrafast Free-electron Laser Beamlines FEL, laser, operation, focusing 58
 
  • F. Frassetto, L. P. Poletto
    CNR-IFN, Padova, Italy
  • M. Kuhlmann, E. Plönjes
    DESY, Hamburg, Germany
  
  We present the design of an ultrafast monochromator explicitly designed for extreme-ultraviolet FEL sources, in particular the upcoming FLASH II at DESY. The design originates from the variable-line-spaced (VLS) grating monochromator by adding a second grating to compensate for the pulse-front tilt given by the first grating after the diffraction. The covered spectral range is 6-60 nm, the spectral resolution is in the range 1000–2000, while the residual temporal broadening is lower than 15 fs. The proposed design minimizes the number of optical elements, since just one grating is added with respect to a standard VLS monochromator and requires simple mechanical movements, since only rotations are needed to perform the spectral scan.  
 
MOP030 Performance Analysis of Variable-Period Helical Undulator with Permanent Magnet for a KAERI THz FEL undulator, permanent-magnet, FEL, simulation 84
 
  • J. Mun, K.H. Jang, Y.U. Jeong, K. Lee, S. H. Park, N. Vinokurov
    KAERI, Daejon, Republic of Korea
  • M.Y. Jeon
    Chungnam National University, Daejoen, Republic of Korea
  
  Funding: This work was supported by the World Class Institute Program of the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT and Future Planning.(NRF Grant Number:WCI2011-001)
We realized a variable-period permanent-magnet helical undulator with high (~1 T) field amplitude, which is almost constant over undulator periods of 23–26 mm. Each undulator period has 4 modular sections of iron poles and permanent magnets embedded in non-magnetic disks with holes along the undulator axis. Modular plates undergo a longitudinal repulsive force from the magnetic field pressure and the spring coils between modular plates. The undulator period can thus be controlled by mechanically changing of the end plate longitudinal position. This compact design is suitable for a table-top terahertz free electron lasers. The measured on-axis field is about 0.97 T with the deviation less than 1% through the whole range of the undulator period variation. The measured spread of the longitudinal coordinates of the undulator field component maxima is less than 1%, and the measured field distribution meets the requirement for our terahertz FEL. The field reproducibility was checked by six measurements of the undulator field after the period variation for the 26 mm period. The r. m. s. phase errors is 3.7 degrees. 		 
 
MOP036 Estimating Effect of Undulator Field Errors using the Radiation Hodograph Method undulator, electron, synchrotron-radiation, free-electron-laser 93
 
  • N.A. Sokolov
    Budker INP & NSU, Novosibirsk, Russia
  • N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  
  Spatially-periodic magnetic structures are widely used for generation of high-brilliance radiation in storage rings, sources of synchrotron radiation and free electron lasers. In 1947, V.L. Ginzburg suggested the first undulator scheme. An alternating magnetic field created by a planar undulator makes electrons oscillate in the transverse direction, with interference of radiation emitted from separate parts of the trajectory. The spectrum of the forward emitted radiation is enchanced due to constructive interference. The ondulator is made of the magnetized bars that are not perfect and their magnetization differs. Therefore, the electron trajectory is not purely sinusoidal and, as a result, the spectral intensity fades. The task was to find out if the precision of magnet manufacturing is sufficient. This paper presents modelling of electron motion in the measured magnetic field of the new (third) free electron laser at the Siberian Synchrotron Radiation Centre. We have managed to estimate the effect of the field errors through comparison of the resulting emitted field amplitude with the amplitude from ideal magnet bars using the hodograph method.  
 
MOP038 Characterization of the Undulator Magnetic Field Quality by the Angle Averaged Radiation Spectrum undulator, electron, photon 100
 
  • O.A. Shevchenko, N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • N. Vinokurov
    KAERI, Daejon, Republic of Korea
  
  The real undulator magnetic field always contains errors which influence undulator performance. The effect of these errors is usually characterized by broadening of the spontaneous emission spectrum at zero angle and corresponding reduction of the spectral intensity. This approach works very well for the phase errors while it does not take into account transversal trajectory displacements. The integrated over the angles radiation spectrum contains more complete information about the undulator field quality but its calculation requires more effort. Therefore the spectral density of emitted radiation (the total number of emitted photons with given energy) can be considered as a figure of merit for an undulator. In this paper we derive analytical formula for this spectrum suitable for doing efficient numerical calculations and demonstrate its application to the case of some typical undulator field errors.  
 
MOP046 Undulator Radiation Damage Experience at LCLS undulator, electron, operation, experiment 127
 
  • H.-D. Nuhn, R.C. Field, Yu.I. Levashov, X.S. Mao, M. Santana-Leitner, J.J. Welch, Z.R. Wolf
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 μm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate. 		 
 
MOP052 Update on FEL Performance for SwissFEL FEL, undulator, simulation, emittance 140
 
  • E. Prat, S. Reiche
    PSI, Villigen PSI, Switzerland
  
  The SwissFEL project under construction at the Paul Scherrer Institute foresees for 2017 the realization of an X-ray FEL with a photon wavelength down to 1 Å. In this paper we present the expected SASE performance for SwissFEL based on input distributions obtained from detailed start-to-end simulation results. The effects of the longitudinal wakefields due to resistive wall and surface roughness in the undulator beamline have been taken into account. We have studied and optimized the impact on the FEL performance of different factors like the electron focusing or the undulator tapering. Results for the standard cases with 200 pC and 10 pC electron bunch charge are shown.  
 
MOP054 Harmonic Lasing Options for LCLS-II undulator, electron, photon, FEL 148
 
  • G. Marcus, Y. Ding, Z. Huang, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • G. Penn
    LBNL, Berkeley, California, USA
  
  Harmonic lasing can be a cheap and relatively efficient way to extend the photon energy range of a particular FEL beamline. Furthermore, in comparison to nonlinear harmonics, harmonic lasing can provide a beam that is more intense, stable, and narrow-band. This paper explores the application of the harmonic lasing concept at LCLS-II using various combinations of phase shifters and attenuators. In addition, a scheme by which individual undulator modules are tuned to amplify either the third or fifth harmonic in different configurations is presented in detail.  
 
MOP055 Start-to-End Simulations for IR/THz Undulator Radiation at PITZ electron, undulator, FEL, simulation 153
 
  • P. Boonpornprasert, M. Khojoyan, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • B. Marchetti, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  • S. Rimjaem
    Chiang Mai University, Chiang Mai, Thailand
  
  High brightness electron sources for modern linac-based Free-Electron Lasers (FELs) have been characterized and optimized at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Since the time structure of the electron bunches at PITZ is identical to those at the European XFEL, the PITZ accelerator is being considered as a proper machine for the development of an IR/THz source prototype for pump and probe experiments planned at the European XFEL. Tunable IR/THz radiation sources using synchrotron radiation from a dipole magnet, transition radiation, high gain FELs and coherent radiation of tailored or premodulated beams are currently under consideration. This work describes start-to-end simulations for generating the FEL radiation using an APPLE-II undulator with electron beams produced by the PITZ accelerator. Analysis of the physical parameter space has been performed with tools of the FAST program code package. Electron Beam dynamics simulations were performed by using the ASTRA code, while the GENESIS 1.3 code was used to study the SASE process. The results of these studies are presented and discussed in this paper.  
 
MOP056 SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime photon, electron, undulator, FEL 159
 
  • I.V. Agapov, G. Geloni
    XFEL. EU, Hamburg, Germany
  • G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
    DESY, Hamburg, Germany
  
  The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime.  
 
MOP058 Purified SASE Undulator Configuration to Enhance the Performance of the Soft X-ray Beamline at the European XFEL undulator, FEL, electron, laser 169
 
  • V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
    DESY, Hamburg, Germany
  • I.V. Agapov, G. Geloni
    XFEL. EU, Hamburg, Germany
  
  The purified SASE (pSASE) undulator configuration recently proposed at SLAC promises an increase in the output spectral density of XFELs. In this article we study a straightforward implementation of this configuration for the soft x-ray beamline at the European XFEL. A few undulator cells, resonant at a subharmonic of the FEL radiation, are used in the middle of the exponential regime to amplify the radiation, while simultaneously reducing the FEL bandwidth. Based on start-to-end simulations, we show that with the proposed configuration the spectral density in the photon energy range between 1.3 keV and 3 keV can be enhanced of an order of magnitude compared to the baseline mode of operation. This option can be implemented into the tunable-gap SASE3 baseline undulator without additional hardware, and it is complementary to the self-seeding option with grating monochromator proposed for the same undulator line, which can cover the photon energy range between about 0.26 keV and 1 keV.  
 
MOP059 Beam Dynamic Simulations for Single Spike Radiation with Short-Pulse Injector Laser at FLASH laser, simulation, operation, electron 173
 
  • M. Rehders
    University of Hamburg, Hamburg, Germany
  • J. Rönsch-Schulenburg
    CFEL, Hamburg, Germany
  • J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • S. Schreiber
    DESY, Hamburg, Germany
  
  Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper discusses the generation of single spike SASE pulses at soft x-ray wavelength at the free-electron laser FLASH by using very short electron bunches of only a few micrometer bunch length. In order to achieve these extremely short bunch lengths, very low bunch charges (in the order of 20 pC) and short electron bunches exiting the photo-injector are required. For this, a new short-pulse injector laser with adjustable rms pulse duration in the range of 0.7 ps to 1.6 ps and bunch charges up to 200 pC was installed, extending the electron beam parameter range before bunch compression in magnetic chicanes. Beam dynamic studies have been performed to optimize the injection and compression of low-charge electron bunches by controlling the effect of coherent synchrotron radiation and space-charge induced bunch lengthening and emittance growth. Optimization includes the pulse parameters of the injector laser. The simulation codes ASTRA, CSRtrack and Genesis 1.3 were employed. 		 
 
MOP061 Electron Beam Delays for Improved Temporal Coherence and Short Pulse Generation at SwissFEL undulator, FEL, electron, simulation 181
 
  • N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  Proposals have been made for the introduction of magnetic electron beam delays in between the undulator modules of a long sectional FEL undulator - these can be used for the generation of trains of FEL pulses which can individually be shorter than the FEL cooperation time [*] or to greatly improve the temporal coherence of the FEL output compared to the nominal SASE configuration [**,***,***]. This paper comprises a feasibility study of the application of these techniques to the SwissFEL hard X-Ray beamline. Three-dimensional simulations are used to investigate the potential photon output.
[*] N.R. Thompson and B.W.J. McNeil, PRL 100:203901, 2008.
[**] N.R. Thompson et al. In Proc IPAC2010, pages 2257–2259, 2010
[***] J. Wu, A. Marinelli, and C. Pellegrini. Proc FEL2012, 2012. 		 
 
MOP063 A Novel Modeling Approach for Electron Beams in SASE FELs FEL, target, electron, operation 190
 
  • P. Niknejadi, J. Madey
    University of Hawaii, Honolulu,, USA
  
  We have recently shown that the Wheeler-Feynman analysis of the interaction of a moving charge with distant absorbers [*] provides a perfect match to the energy radiated by two coherently oscillating charged particles (a heretofore unsolved problem in classical electrodynamics) [**]. Here we explain the need to include the Wheeler-Feynman coherent radiation reaction force as an integral part of the solution of the boundary value problem of free electron lasers (FELs) that radiate into “free space”. We will also discuss how the advanced field of the absorber can interact with the radiating particles at the time of emission. Finally we will introduce and explore the possibility of improving the temporal coherence in the self amplified spontaneous emission (SASE) FELs as well as the possibility of optimizing the spectrum of the emitted coherent radiation by SASE FELs via altering the structure of their targets by including the Wheeler-Feynman coherent radiation reaction force in the analysis of FEL operations.
* Wheeler, J. A.; Feynman, R. P, Rev. Mod. Phys. 17, 157, 1945.
** P. Niknejadi et al. "Energy Conservation of Coherently Oscillating Charged Particles in Classical Electrodynamics" submitted. 		 
 
MOP064 Statistical Properties of the Radiation from SASE FEL Operating in a Post-saturation Regime with and without Undulator Tapering FEL, undulator, free-electron-laser, laser 194
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  We describe statistical and coherence properties of the radiation from x-ray free electron lasers (XFEL) operating in the post-saturation regime. We consider practical case of the SASE3 FEL at European XFEL. We perform comparison of the main characteristics of X-ray FEL operating in the post-saturation regime with and without undulator tapering: efficiency, coherence time and degree of transverse coherence.  
 
MOP065 Optimization of a High Efficiency FEL Amplifier electron, undulator, FEL, laser 199
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  The problem of an efficiency increase of an FEL amplifier is now of great practical importance. Technique of undulator tapering in the post-saturation regime is used at the existing x-ray FELs LCLS and SACLA, and is planned for use at the European XFEL, Swiss FEL, and PAL XFEL. There are also discussions on the future of high peak and average power FELs for scientific and industrial applications. In this paper we perform detailed analysis of the tapering strategies for high power seeded FEL amplifiers. Application of similarity techniques allows us to derive universal law of the undulator tapering.  
 
MOP066 An Overview of the Radiation Properties of the European XFEL electron, operation, undulator, hardware 204
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  We present an overview of the radiation properties of the European XFEL based on recently accepted strategy of operation at the fixed set of electron energies (8.5 GeV, 12 GeV, 14 GeV, and 17.5 GeV), baseline parameters if the electron beam, and new set undulator parameters. We also discuss potential extension of the parameter space which does not require new hardware and can be realized at a very early stage of the European XFEL operation.  
 
MOP075 Laser Seeding Schemes for Soft X-rays at LCLS-II undulator, laser, electron, bunching 223
 
  • G. Penn
    LBNL, Berkeley, California, USA
  • P. Emma, E. Hemsing, G. Marcus, T.O. Raubenheimer, L. Wang
    SLAC, Menlo Park, California, USA
  
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515.
The initial design for LCLS-II incorporates both SASE and self-seeded configurations. Increased stability and/or coherence than is possible with either configuration may be provided by seeding with external lasers followed by one or more stages of harmonic generation, especially in the soft x-ray regime. External seeding also allows for increased flexibility, for example the ability to quickly vary the pulse duration. Studies of schemes based on high-gain harmonic generation and echo-enabled harmonic generation are presented, including realistic electron distributions based on tracking through the injector and linac. 		 
 
MOP078 Measurements of FEL Polarization at FERMI polarization, FEL, experiment, electron 231
 
  • E. Allaria
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  We report detailed quantitative characterization of different polarization states of a single-pass, externally-seeded FEL operating with variable polarization undulators in the VUV spectral range. The experiment has been performed at FERMI FEL-1 operated in the 52–26 nm wavelength range. Three different, independent polarimeter setups, installed at the end of ex- perimental beamlines, have been used to characterize the four “pure” polarization states: horizontal, vertical, right-circular and left-circular. The impact of downstream transport optics upon the radia- tion polarization has been assessed; at longer wavelengths, dichroism effects lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other and allow a cross-calibration of the instruments.
On behalf of the team organized for polarization measurements at FERMI. 		 
 
MOP079 Generation of Multiple Coherent Pulses in a Superradiant Free-Electron Laser electron, FEL, undulator, simulation 233
 
  • X. Yang, S. Seletskiy
    BNL, Upton, Long Island, New York, USA
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  
  We analyze the structure of the tail of a superradiant pulse, which is constituted by a train of sub-pulses with decaying amplitudes. We show how a trailing pulse, with pi phase advance from the leading pulse, is generated at the falling edge of the leading superradiant pulse, where the corresponding phase space is deeply saturated and the electrons become de-trapped by the reduced ponderomotive potential. Once the trailing pulse gains enough energy, it generates a second trailing pulse, and the process takes place again. By performing detailed simulations of the resulting electron phase space distribution and the FEL pulse spectral and temporal structure with PERSEO, we confirm that the deformation and re-bunching of the longitudinal phase space create a sequence of pulses. These results are compared to 3D simulations using the FEL code GENESIS 1.3 showing a good agreement.  
 
MOP083 Start-to-End Simulation for FLASH2 HGHG Option simulation, undulator, electron, FEL 244
 
  • G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov
    DESY, Hamburg, Germany
  • K.E. Hacker
    DELTA, Dortmund, Germany
  • T. Plath
    Uni HH, Hamburg, Germany
  
  The Free-electron laser in Hamburg (FLASH) is the first FEL user facility to have produced extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade of FLASH named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections, a seeding undulator section and a SASE undulator section. In this paper, results from a start-to-end simulation for a FLASH2 High-Gain Harmonic Generation (HGHG) option are presented. For the beam dynamics simulation, space charge, coherent synchrotron radiation (CSR) and longitudinal cavity wake field effects are taken into account. In order to get electron beam bunches with small correlated and uncorrelated energy spread, RF parameters of the accelerating modules have been optimized as well as the parameters of the bunch compressors. Radiation simulations for the modulator and the radiator have been done with code Genesis 1.3 by using the particle distribution generated from the beam dynamics simulation. The results show that for a single stage HGHG, 33.6 nm wavelength FEL radiation can be seeded at FLASH2 with a 235 nm seeding laser.  
 
MOP084 Enhancing Coherent Harmonic Generation using Tilted Laser Wavefronts laser, electron, synchrotron, synchrotron-radiation 248
 
  • S. Khan
    DELTA, Dortmund, Germany
  
  Funding: Work supported by BMBF (contract 05K13PE3)
Coherent Harmonic Generation (CHG) to produce ultrashort pulses of synchrotron radiation is based on the interaction of relativistic electrons in a storage ring with femtosecond laser pulses in an undulator. The resulting periodic energy modulation can be converted to a density modulation by a dispersive chicane, giving rise to coherent emission at harmonics of the laser wavelength in a second undulator. If the first undulator is in a section with non-zero dispersion, the density modulation can be enhanced using tilted laser wavefronts, thus delaying the phase-space distributions of electrons with different energy with respect to each other. The most simple way to realize the wavefront tilt would be to introduce a small crossing angle between the electron and laser beam. Details are discussed for the case of the CHG short-pulse facility at DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, but HGHG and EEHG seeding of free-electron lasers could also be performed this way. 		 
 
MOP086 Broadly Tunable THz FEL Amplifier FEL, laser, undulator, electron 252
 
  • C.H. Chen, F.H. Chao, Y.C. Chiu, Y.K. Gan, K.Y. Huang, Y.-C. Huang, Y.C. Wang
    NTHU, Hsinchu, Taiwan
  
  Funding: MOST 102-2112-M-007 -002 -MY3, Taiwan
In this paper we present a broadly tunable sub-MW THz FEL amplifier driven by a photoinjector with a sub-kW seed THz source tunable between 0.7-2.0 THz. Specifically an S-band photoinjector at 2.856 GHz generate a 3.3-5.5 MeV electron bunch with 0.5 nC charge in a 4.25 ps rms bunch length, which is injected into a 2-m long undulator with a period of 18 mm and an rms undulator parameter of 0.98. The driver laser of the photoinjector is a frequency quadrupled amplified, mode-locked Nd:YVO4 laser at 1064 nm. We recycle the unconverted infrared laser at 1064 nm to pump a THz parametric amplifier using a lithium niobate crystal as its gain crystal. This THz parametric amplifier generates a transform-limited THz pulse with sub-kW power between 0.7 and 2.0 THz, which is seeded into the undulator to produce broadly tunable, transform-limited, sub-MW THz radiation through FEL amplification with a gain of about 3000. Since the pump laser of the THz OPA is derived from the driver laser of the photoinjector, the seed THz pulse is fully synchronized and overlapped with the electron bunch. Experimental progress of this work will be presented in the conference.
*Work supported by MoST under NSC 102-2112-M-007-002-MY3
 		 
poster icon Poster MOP086 [1.269 MB]  
 
MOP087 Upgrade Plans for the Short-pulse Facility at DELTA laser, electron, undulator, dipole 255
 
  • S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, P. Ungelenk
    DELTA, Dortmund, Germany
  
  Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
DELTA is a 1.5-GeV synchrotron light source operated by the TU Dortmund University with a short-pulse facility based on Coherent Harmonic Generation (CHG) * to produce radiation with wavelengths in the VUV regime. Even shorter wavelengths can be generated by an upgrade based on the Echo-Enabled Harmonic Generation (EEHG) technique ** which requires additional magnetic chicanes and undulators. A new storage ring lattice provides enough free space for an EEHG setup and additionally for a femtoslicing undulator. Besides the new optics, first simulation results of EEHG will be presented.
* S. Khan et al., Sync. Rad. News 26, 3 (2013).
** G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009). 		 
 
MOP088 High Repetition Rate Energy Modulator System Utilizing a Laser Enhancement Cavity laser, cavity, electron, resonance 260
 
  • Y. Honda
    KEK, Ibaraki, Japan
  
  A high intensity laser field can be realized at a high repetition rate using an enhancement optical cavity scheme. We propose to apply the 100GW-level laser field inside the cavity for producing a micro-bunch structure in an electron bunch. Combining this system with an ERL scheme of accelerator, it can be used for a seeded FEL at a high repetition rate of ~100MHz continuous beam. The longitudinal electric field at the center area of a higher-order transverse mode of laser can be used to modulate beam energy at a period of the laser wavelength. A 250 MeV class two-loop ERL accelerator has been proposed in KEK as a future upgrade plan of existing 35 MeV ERL test accelerator. It will be able to provide a low emittance, small energy spread, short bunch electron beam at a high repetition rate of continuous operation. We propose to apply this beam to produce a seeded VUV coherent radiation. We will discuss the feasibility of the scheme and status of the laser modulator development.  
 
MOP090 Soft X-ray Self-seeding Simulation Methods and their Application for LCLS undulator, simulation, FEL, optics 264
 
  • S. Serkez
    DESY, Hamburg, Germany
  • Y. Ding, Z. Huang, J. Krzywinski
    SLAC, Menlo Park, California, USA
  
  Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. We study radiation propagation through the grating monochromator installed at LCLS. The monochromator design is based on a toroidal variable line spacing grating working at a fixed incidence angle mounting without an entrance slit. It covers the spectral range from 500eV to 1000eV. The optical system was studied using wave optics method to evaluate the performance of the self-seeding scheme. Our wave optics analysis takes into account the finite size of the coherent source, third-order aberrations and height error of the optical elements. Wave optics is the only method available, in combination with FEL simulations, to simulate performance of the monochromator without exit slit. Two approaches for time-dependent simulations are presented, compared and discussed. Also pulse-front tilt phenomenon effect is illustrated.  
 
MOP092 X-ray Monochromators for Self-seeding XFELs in the Photon Energy Range Starting from 1.5 keV photon, FEL, scattering, electron 269
 
  • Yu. Shvyd'ko
    ANL, Argonne, Ilinois, USA
  
  Self-seeding of XFELs below 1 keV can be performed using grating monochromators [1]. Forward-Bragg diffraction (wake) monochromators [2] were instrumental for achieving self-seeding in hard x-ray FELs in the photon energy range from 5 to 10 keV [3]. Large photo-absorption makes extension into the lower photon range difficult. Here alternative schemes of x-ray monochromators are introduced and discussed for achieving self-seeding in a yet inaccessible spectral range starting from 1.5 keV.
[1] J. Feldhaus, et al., Opt. Commun. 140, 341 (1997).
[2]. G. Geloni, V. Kocharyan, and E. Saldin, J. Mod. Opt. 58, 1391 (2011).
[3] J. Amann, et al., Nat. Photonics 6, 693 (2012).
 		 
 
MOP095 HGHG AND EEHG MICROBUNCHES WITH CSR AND LSC simulation, electron, FEL, dipole 275
 
  • K.E. Hacker
    DELTA, Dortmund, Germany
  
  Funding: Work supported by BMBF (contract 05K13PE3) and DESY
Longitudinal space charge (LSC) forces in a drift and coherent synchrotron radiation (CSR) in a chicane are relevant for high gain harmonic generation (HGHG) and echo enabled harmonic generation (EEHG) seeding designs. These factors determine whether or not the modulator can be located significantly upstream of the radiator. The benefits and dangers of having a drift in between the radiator and the modulator are investigated and a measurement of the LSC enabled reduction of the energy spread of a seeded beam is presented. 		 
 
MOC03 Radiation Properties of Tapered Hard X-ray Free Electron Lasers electron, FEL, undulator, simulation 300
 
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • S.D. Chen
    NCTU, Hsinchu, Taiwan
  • K. Fang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • S. Serkez
    DESY, Hamburg, Germany
  
  We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.  
slides icon Slides MOC03 [3.797 MB]  
 
MOC04 Chirped and Modulated Electron Pulse Free Electron Laser Techniques electron, undulator, FEL, simulation 303
 
  • J. Henderson, L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  
  Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20
A potential method to improve the free electron laser's output when the electron pulse has a large energy spread is investigate and results presented. A simplified model is the first given, in which there are a number of linearly chirped beamlets equally separated in energy and time. By using chicanes, radiation from one chirped beamlet is passed to the next, helping to negate the effect of the beamlet chirps and maintaining resonant interactions. Hence the addition of chicane allow the electrons to interact with a smaller range of frequencies (Δ ω <2 ρ γr), sustaining the FEL interaction. One method to generate such a beamlet structure is presented and is shown to increase FEL performance by two orders of magnitude. 		 
slides icon Slides MOC04 [6.777 MB]  
 
TUB02 Generation of Intense XVUV Pulses with an Optical Klystron Enhanced Self- amplified Spontaneous Emission Free Electron Laser FEL, klystron, electron, laser 332
 
  • G. Penco, E. Allaria, G. De Ninno, E. Ferrari, L. Giannessi
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • G. De Ninno
    University of Nova Gorica, Nova Gorica, Slovenia
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  
  Fermi is a seeded FEL operating in high gain harmonic generation mode. The FEL layout is constituted by a modulator and six radiators separated by a dispersive section. The modulator and the radiators can be tuned to the same resonant frequency to set up an asymmetric optical klystron configuration where self amplified spontaneous emission can be generated and studied. This paper presents the experiment consisting in the analysis of the enhancement of the self-amplified spontaneous emission (SASE) radiation by the dispersion in the optical klystron. The FEL pulses produced with the optical klystron configuration are several order of magnitude more intense than in pure SASE mode with the dispersion set to zero, The experimental observations are in good agreement with simulation results and theoretical expectations. A comparison with the typical high-gain harmonic generation seeded Fel operation is also provided.  
slides icon Slides TUB02 [12.835 MB]  
 
TUP006 Two-color Free-electron Laser via Two Orthogonal Undulators FEL, polarization, undulator, electron 358
 
  • N.S. Mirian
    IPM, Tehran, Iran
  • G. Dattoli
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • V. Petrillo
    Universita' degli Studi di Milano, Milano, Italy
  
  An amplifier Free electron Laser (FEL) including two orthogonal polarized undulators with different periods and field intensities is able to emit two color radiations with different frequency and polarization while the total length of device does not change respect to usual single color FELs. The wavelengths of two different colors can be changed by choosing different periods, while variation in the magnetic strengths can be used to modify the gain lengths.  
 
TUP007 Spectral Limits and Frequency Sum-rule of Current and Radiation Noise Measurement electron, distributed, undulator, FEL 362
 
  • A. Gover, R. Ianconescu
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • A. Nause
    UCLA, Los Angeles, USA
  
  Funding: This research was supported by a grant from the United States-Israel Binational Science Foundation(BSF), Jerusalem, ISRAEL
The current noise spectrum of an electron beam is generally considered white and expressed by the shot-noise formula (eI0). It is possible to control the spectral energy of a random electron beam current by longitudinal space charge microdynamics and dispersive transport. Both noise suppression (relative to eI0)[1,2] and noise enhancement[3] have been demonstrated, exhibiting sub/super-Poissonian particle distribution statistics, respectively. We present a general theory for the current noise of an e-beam and its radiation emission in the entire spectrum. The measurable current noise spectrum is not white. It is cut-off at high frequencies, limited by the measurement length and the beam axial momentum spread (fundamentally limited by quantum uncertainty). We show that under certain conditions the current noise spectrum satisfies a frequency sum-rule: exhibiting noise enhancement in one part of the spectrum when suppressed at another part and vice versa. The spontaneous emission (radiation noise) into a single radiation mode or single direction in any scheme (OTR, Undulator etc.) is sub-radiant when the beam current is sub-Poissonian and vice versa, but the sum-rule does not apply. 		 
 
TUP009 A Simple Method for Generating a Few Femtosecond Pulses in Seeded FELs electron, laser, FEL, linac 371
 
  • H.T. Li, Z.G. He, Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Work supported by Major State Basic Research Development Program of China (2011CB808301) and the Fundamental Research Funds for the Central Universities of China (WK2310000045)
We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the centre part of electron beam and short pulses in high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse with duration of 8 femtoseconds (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 m. 		 
 
TUP012 Numerical Simulation of a Super-radiant THz Source Driven by Femtosecond Electron Bunches electron, undulator, FEL, emittance 374
 
  • R.V. Chulkov
    B.I. Stepanov Institute of Physics, Belarus, Russia
  • V.A. Goryashko
    Uppsala University, Uppsala, Sweden
  • V. Zhaunerchyk
    University of Gothenburg, Gothenburg, Sweden
  
  Funding: We would like to acknowledge the financial support from the Swedish FEL center.
Pulsed THz FELs are typically driven by rf Linacs which produce intense electron bunches with a duration of a few picoseconds or even shorter. When the bunch duration is less than a picosecond, the wavelength of the THz light is greater than the bunch length and the FEL operates in the super-radiant (SR) regime*. In the report, we summarize our studies performed for an SR source operating in the THz frequency range. In particular, we focus on an open-type planar undulator comprising no guiding structure. Using a numerical code that supports 3D modeling of the SR dynamics as well as statistical properties of electron bunches, we analyze influence of electron bunch parameters on generated THz radiation and reveal some surprising results. More specifically, for the considered undulator configuration, we predict degradation in the angular divergence and spectral broadening of the generated radiation as the electron bunch emittance decreases. We also demonstrate how electron bunch broadening associated with the electron energy spread can eventually be suppressed.
* R. Chulkov, V. Goryashko, and V. Zhaunerchyk, Report III of the series of reports by the Swedish FEL Center and FREIA Group, http://www.diva-portal.org/smash/get/diva2:699684/FULLTEXT01.pdf. 		 
poster icon Poster TUP012 [1.553 MB]  
 
TUP013 X-Ray Smith-Purcell Radiation from a Beam Skimming a Grating Surface target, electron, factory, free-electron-laser 378
 
  • D.Yu. Sergeeva, A.A. Tishchenko
    MEPhI, Moscow, Russia
  
  Smith-Purcell radiation as a base of Free Electron Lasers is actively studied experimentally and by simulating. Usually the beam is supposed to move at some distance above the target. In practice the distance is tried to decrease so that the beam passes very close to the target surface. Experimental data contains the information about grating heating. The authors of article* suggested the cause of the heating is that the beam skims the grating surface. Developing the method used in**,*** we give the analytical description of the X-Ray radiation arising when the beam of charge particles moves parallel above the periodical target, but the part of the beam crosses the target. The radiation arising is the superposition of Smith-Purcell radiation and transition radiation from the grating. This radiation determines the process of beam bunching and following gain of radiation.
*H.L.Andrews et al,Phys. Rev. ST AB 12 (2009) 080703
**A.A.Tishchenko, A.P.Potylitsyn, M.N.Strikhanov, Phys. Rev. E 70 (2004) 066501
***D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189 		 
 
TUP014 Forward X-Ray and Ultraviolet Smith-Purcell Radiation for FEL target, electron, polarization, plasma 384
 
  • A.A. Tishchenko, D.Yu. Sergeeva
    MEPhI, Moscow, Russia
  
  The scheme of Free Electron Lasers based on Smith-Purcell effect is well known to describe the process of interaction between an electron beam and evanescent wave, which bunches this beam. In this work we concentrate on the process of generation of the radiation propagating at small angles. In terms of approach described in detail in*,**, we investigate the Smith-Purcell radiation at oblique incidence of a single charged particle for X-Ray and UV frequency region. This forward radiation propagates through all the region of the beam moving and provides more close interaction between the beam and the radiation, than usual surface waves existing in FELs. Spectral and angular characteristics of the forward radiation are discussed from point of view its role in Smith-Purcell based FELs.
*A.P.Potylitsyn, M.I.Ryazanov, M.N.Strikhanov, A.A.Tishchenko, Diffraction Radiation from Relativistic Particles, Springer, 2011
**D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189 		 
 
TUP015 Radiation and Interaction of Layers in Quasi-plane Electron Bunches Moving in Undulators electron, undulator, laser, free-electron-laser 388
 
  • N. Balal
    Ariel University, Ariel, Israel
  • V.L. Bratman
    IAP/RAS, Nizhny Novgorod, Russia
  
  The model of radiating planes (1D radiating gas) consisting of electrons that oscillate and travel with a relativistic translational velocity allows one to develop a simple general theory describing a number of important effects of radiation in a undulator for dense electron bunches formed in photoinjector accelerators. Having based on this method and taking into account both Coulomb and radiation interactions of the planes with an arbitrary density, particle velocity distribution and energy chirp we have found analytically and numerically efficiency and frequency spectrum for coherent spontaneous radiation, including conditions for generation of minimum narrow and very broadband spectra. The developed theory has been applied for estimation of a powerful terahertz radiation source with a moderate energy of electrons.  
 
TUP016 Quasi-optical Theory of Terahertz Superradiance from an Extended Electron Bunch electron, simulation, resonance, wakefield 391
 
  • N.S. Ginzburg, A. Malkin, A. Sergeev, V.Yu. Zaslavsky, I.V. Zotova
    IAP/RAS, Nizhny Novgorod, Russia
  
  Funding: This study was supported by the Russian Foundation for Basic Research (project no. 14-08-01180) and the Dynasty Foundation.
We consider superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multi-megawatt terahertz pulses*. To study the above process we have developed a three-dimensional, self-consistent, quasi-optical theory of Cherenkov stimulated emission which includes a description of the formation of evanescent waves near the corrugated surface and its excitation by RF current induced in the electron bunch. Results obtained in the framework of a quasi-optical model were confirmed by direct CST STUDIO PIC simulations. There is a possibility of advancement towards still shorter wavelengths (infrared and optical), which can be achieved by decreasing the period of the diffraction gratings and increasing the density and energy of the particles in the electron bunches. Increase of coupling impedance can be obtained by using inclined incidence of electron bunch on corrugated surface (clinotron configuration).
Ginzburg N.S et al. Phys. Rev. Lett. 2013. V.110, Iss.18. 184801.
 		 
 
TUP017 Using Lorentz Transformations for Simulations of Wiggler Superradiance from the Picosecond Electron Bunches electron, undulator, simulation, scattering 395
 
  • A. Malkin, N.S. Ginzburg, A.A. Golovanov, I.V. Zotova
    IAP/RAS, Nizhny Novgorod, Russia
  • V.P. Tarakanov
    LPI, Moscow, Russia
  
  Funding: This work was supported by Russian Foundation for Basic Research under Grant No 12-02-01152.
In this paper we present a theoretical analysis of superradiance (SR) from picosecond electron bunches wiggling in periodical undulator field based both on the method of averaged ponderomotive force and on a direct numerical PIC (particle-in-cell) simulation. Within both approaches the analysis takes place in the reference frame co-moving with electrons which allows simplifying the procedure of simulation significantly due to the fact that all the spatial scales including the radiation wavelength, the length of the beam and the length of the pump field pacet into which the undulator field is transformed are of the same order. We show that in the reference frame the SR effect can be interpreted as a formation of the distributed Bragg mirror in the bulk of the electron beam which is effectively reflecting (scattering) the pump wave. A possibility of generation of multimegawatt pulses in terahertz and far infrared wave ranges is demonstrated. 		 
 
TUP019 Update on the FEL Code Genesis 1.3 electron, undulator, lattice, FEL 403
 
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  The widely used time-dependent code Genesis 1.3 has been modified to address new needs of users worldwide. The existing limitation of tracking isolated slices of the FEL beam has been overcome by keeping the entire electron beam in memory, which is tracked as a whole through the undulator. This modification allows for additional features such as allowing particles to migrate into other slices or applying self-consistent wakefield and space charge models.  
 
TUP023 Modeling CSR in a Vacuum Chamber by Partial Fourier Analysis and the Discontinuous Galerkin Method synchrotron-radiation, impedance, synchrotron, vacuum 419
 
  • D. A. Bizzozero, J.A. Ellison
    UNM, Albuquerque, New Mexico, USA
  • R.L. Warnock
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by DOE contracts DE-FG-99ER41104 and DE-AC03-76SF00515.
We continue our study of CSR* from a bunch on an arbitrary curved orbit in a plane, which used a Fourier transform in s-ct. The vacuum chamber has rectangular cross section with possibly varying horizontal width. We use the slowly varying amplitude approximation, and invoke a Fourier expansion in the vertical coordinate y, which meets the boundary conditions on the top and bottom plates and makes contact with the Bessel equation of the frequency domain treatment. The fields are defined by a PDE in s and x, first order in s, which is discretized in x by finite differences (FD) or the discontinuous Galerkin method (DG). We compare results of FD and DG, and also compare to our earlier calculations in 3D (paraxial) which did not use the Fourier series in y*,**. This approach provides more transparency in the physical description, and when only a few y-modes are needed, provides a large reduction in computation time.
* See FEL13 Proceedings MOPSO06: http://accelconf.web.cern.ch/AccelConf/FEL2013/papers/mopso06.pdf
** See PRST-AB 7 054403 (2004) and Jpn. J. Appl. Phys. 51 016401 (2012).
 		 
 
TUP025 TW X-ray Free Electron Laser Optimisation by Transverse Pulse Shaping electron, FEL, undulator, simulation 425
 
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  
  We study the dependence of the peak power of a 1.5 Angstrom TW, tapered X-ray free-electron laser on the transverse electron density distribution. Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of 1.5 Angstrom using the fully 3-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30-70 % reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian.  
 
TUP026 Transverse Coherence Properties of a TGU-based FEL FEL, electron, undulator, emittance 429
 
  • P. Baxevanis, Z. Huang, R.D. Ruth
    SLAC, Menlo Park, California, USA
  • C.B. Schroeder
    LBNL, Berkeley, California, USA
  
  The use of a transverse gradient undulator (TGU) is considered an attractive option for FELs driven by electron beams with a relatively large energy spread. In this scheme, a dispersion is introduced in the beam while the undulator poles are inclined so that the undulator field acquires a linear dependence upon the transverse position in the direction of dispersion. By suitably selecting the dispersion and the field gradient, the energy spread effect can be significantly mitigated, thus avoiding a drastic reduction in the FEL gain. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the output FEL radiation can become significant. To investigate this effect, we study the properties of the higher-order eigenmodes of a TGU-based, high-gain FEL, using both a simplified, analytically-solvable model and a variational technique. This formalism is then used to provide an estimate of the degree of transverse coherence for a representative soft X-ray, TGU FEL example.  
 
TUP027 Initial Value Problem for an FEL Driven by an Asymmetric Electron Beam FEL, electron, undulator, simulation 433
 
  • P. Baxevanis, R.D. Ruth
    SLAC, Menlo Park, California, USA
  
  FEL configurations in which the driving electron beam is not axially symmetric (round) are important in the study of novel concepts (such as TGU-based FELs) but also become relevant when one wishes to explore the degree to which the deviation from symmetry-inevitable in practical cases-affects the performance of more conventional FEL schemes. In this paper, we present a technique for solving the initial value problem of such an asymmetric FEL. Extending an earlier treatment of ours, we start from a self-consistent, fully 3D, evolution equation for the complex amplitude of the electric field of the FEL radiation, which is then solved by expanding the radiation amplitude in terms of a set of orthogonal transverse modes. The numerical results from such an analysis are in good agreement with simulation and provide a full description of the radiation in the linear regime. Moreover, when the electron beam sizes are constant, this approach can be used to verify the predictions of the standard eigenmode formalism.  
 
TUP029 iSASE Study electron, FEL, undulator, simulation 442
 
  • K. Fang
    Indiana University, Bloomington, Indiana, USA
  • S.D. Chen
    NCTU, Hsinchu, Taiwan
  • S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.  
 
TUP030 Mode Component Evolution and Coherence Analysis in Terawatt Tapered FEL FEL, electron, undulator, laser 446
 
  • K. Fang, S.D. Chen, X. Huang, C. Pellegrini, J. Wu
    SLAC, Menlo Park, California, USA
  • S.D. Chen
    NCTU, Hsinchu, Taiwan
  • C. Emma, C. Pellegrini
    UCLA, Los Angeles, USA
  • K. Fang
    Indiana University, Bloomington, Indiana, USA
  • C.-S. Hwang
    NSRRC, Hsinchu, Taiwan
  • S. Serkez
    DESY, Hamburg, Germany
  
  A fast and robust algorithm is developed to decompose FEL radiation field transverse distribution into a set of orthonormal basis. Laguerre Gaussian and Hermite Gaussian can be used in the analysis. The information of mode components strength and Gaussian beam parameters allows users in downstream better utilize FEL. With this method, physics of mode components evolution from starting stage, to linear regime and post saturation are studied with detail. With these decomposed modes, correlation function can be computed with less complexity. Eigenmodes of the FEL system can be solved using this method.  
 
TUP031 FEL Code Comparison for the Production of Harmonics via Harmonic Lasing FEL, electron, simulation, undulator 451
 
  • G. Marcus, W.M. Fawley
    SLAC, Menlo Park, California, USA
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Harmonic lasing offers an attractive option to significantly extend the photon energy range of FEL beamlines. Here, the fundamental FEL radiation is suppressed by various combinations of phase shifters, attenuators, and detuned undulators while the radiation at a desired harmonic is allowed to grow linearly. The support of numerical simulations is extensively used in evaluating the performance of this scheme. This paper compares the results of harmonic growth in the harmonic lasing scheme using three FEL codes: FAST, GENESIS, and GINGER.  
 
TUP032 FEL Simulation and Performance Studies for LCLS-II electron, undulator, FEL, simulation 456
 
  • G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang, J. Wu
    SLAC, Menlo Park, California, USA
  
  The design and performance of the LCLS-II free-electron laser beamlines are presented using start-to-end numerical particle simulations. The particular beamline geometries were chosen to cover a large photon energy tuning range with x-ray pulse length and bandwidth flexibility. Results for self-amplified spontaneous emission and self-seeded operational modes are described in detail for both hard and soft x-ray beamlines in the baseline design.  
 
TUP035 Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS undulator, polarization, simulation, bunching 465
 
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • Z. Huang, A. Lutmann, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner
    SLAC, Menlo Park, California, USA
  
  Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515
A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes.
* Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013).
** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013). 		 
 
TUP036 Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls experiment, simulation, electron, free-electron-laser 470
 
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
  
  In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".  
 
TUP040 Flying RF Undulator undulator, electron, resonance, focusing 474
 
  • A.V. Savilov, I.V. Bandurkin, S.V. Kuzikov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  
  A new concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the -1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton’s photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse. This work is supported by the Russian Foundation for Basic Research (Projects 14-08-00803 and 14-02-00691).  
poster icon Poster TUP040 [0.189 MB]  
 
TUP042 High Efficiency Lasing with a Strongly Tapered Undulator undulator, laser, electron, experiment 478
 
  • J.P. Duris, P. Musumeci
    UCLA, Los Angeles, California, USA
  
  Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073 and University of California Office of the President award 09-LR-04-117055-MUSP.
Typical electrical to optical energy conversion efficiencies for FELs are limited by the Pierce parameter to 10-3 or smaller. Undulator tapering schemes have enabled extraction of as much as 1 or 2% of the electron energy. Recently, the UCLA BNL helical inverse free electron laser (IFEL) experiment at ATF demonstrated energy doubling and acceleration of 30% of an electron beam from 52 to 93 MeV with a modest 1011 W power CO2 laser pulse. By reversing and retuning the undulator, the electrons may be violently decelerated, thereby transferring energy from the beam to the laser pulse. Simulations show that by sending a 1 kA, 70 MeV electron beam and 100 GW laser into a prebuncher and the reversed undulator, 41% of the electron beam energy should be converted to radiation, allowing the laser pulse power to grow to 127 GW. 		 
 
TUP045 IFEL Driven Micro-Electro-Mechanical System Free Electron Laser undulator, electron, FEL, laser 481
 
  • N.S. Sudar, J.P. Duris, P. Musumeci
    UCLA, Los Angeles, USA
  
  The Free Electron Laser has provided modern science with a tunable source of high frequency, high power, coherent radiation. To date, short wavelength FEL's have required large amounts of space in order to achieve the necessary beam energy to drive the FEL process and to reach saturation of the output radiation power. By utilizing new methods for beam acceleration as well as new undulator technology, we can decrease the space required to build these machines. In this paper, we investigate a scheme by which a tabletop XUV FEL might be realized. Utilizing the Rubicon Inverse Free Electron Laser (IFEL) at BNL together with micro-electro-mechanical system (MEMS) undulator technology being developed at UCLA, we propose a design for a compact XUV FEL.  
 
TUP046 Terahertz FEL based on Photoinjector Beam in RF Undulator undulator, focusing, electron, FEL 485
 
  • S.V. Kuzikov, I.V. Bandurkin, M.E. Plotkin, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • A.V. Savilov
    NNGU, Nizhny Novgorod, Russia
  
  Photoinjectors, which can produce picosecond electron bunches of MeV-level, are attractive for THz generation. Fortunately, a long distance to reach scattering power saturation in FEL is not necessary, if bunch length is shorter than the produced THz half-wavelength. However, the energy of several MeVs does not allow providing long traveling of the flying bunch without longitudinal divergence. That is why, we suggest using specific RF undulator in a form of the normal wave in the helical waveguide at 3 cm wavelength. The mentioned wave has the -1st space harmonic with transverse fields and negative phase velocity (responsible for particle wiggling). This wave has also the 0th harmonic with longitudinal field and positive phase velocity equal to bunch velocity. Due to the synchronous 0th harmonic one can channel low-energy bunches (due to longitudinal focusing field) as far as several meters distance. One might also inject electron bunches in slightly accelerating field, in this case the output THz pulse obtain nearly linear frequency modulation. Such long THz pulses with the mentioned modulation of the frequency can be effectively compressed by pair of diffraction gratings.  
poster icon Poster TUP046 [2.914 MB]  
 
TUP047 Chirped Pulse Superradiant Free-electron Laser electron, undulator, laser, FEL 489
 
  • Y.-C. Huang, C.H. Chen
    NTHU, Hsinchu, Taiwan
  • J. Wu, Z. Zhang
    SLAC, Menlo Park, California, USA
  
  Funding: This work is supported by Ministry of Science and Technology under Contract NSC 102-2112-M-007-002-MY3
When a short electron bunch traverses an undulator and radiates a wavelength significantly longer than the bunch length, the electrons quickly loses energy through so-called superradiance and generate a negatively chirped radiation frequency at the output. In this paper, we develop a theory to describe this chirped-pulse radiation and numerically demonstrate pulse compression by using a quadratic phase filter. As a design example at THz, a photoinjector/linac system generates a 15 MeV electron bunch containing 15-pC charge in a 60-fs duration. The electrons radiate a chirped pulse at 2.5 THz from a 1.5 m long undulator with a period of 5.6 cm and undulator parameter of 1.7. By using a grating pair, the output THz field can be compressed from 27 to 3 cycles. As another example at EUV, a future dielectric laser accelerator [1] is assumed to generate a 100 MeV electron bunch containing 75-fC charge in 1-nm long length. The electrons radiate a chirped EUV pulse at 13.5 nm from a 15.8 cm long dielectric laser undulator [2] with a period of 1.05 mm and undulator field of 3.3 T. By using a quadratic phase filter as a pulse compressor, the peak power of the EUV radiation is increased from 0.7 to 10 kW.
*Y.C. Huang and R.L. Byer, Appl. Phys. Lett. 69 (15), (1996) 2185-2177.
**T. Plettner, R. L. Byer., Phys. Rev. ST Accel. Beams 11, (2008) 030704. 		 
 
TUP054 Status of Electron Beam Slicing Project at NSLS-II, BNL electron, storage-ring, photon, linac 496
 
  • A. He, F.J. Willeke, L.-H. Yu
    BNL, Upton, Long Island, New York, USA
  
  The Electron Beam Slicing (e-beam slicing) at NSLS-II, Brookhaven National Laboratory, supported by the Laboratory Directed Research and Development (LDRD) Program, is focused on the development of the new method to generate ultra-short x-ray pulses using focused short low energy (∼20 MeV) electron bunches to create short slices of electrons from the circulating electron bunches in a synchrotron radiation storage ring. The e-beam slicing activities are staged in 3 main phases. In Phases 0, the theory of e-beam slicing is developed, the low energy linac compressor is simulation designed, the radiation separation between the satellite and core is analyzed by simulation and the properties of the e-beam slicing system are discussed and compared with other ultra-short x- ray sources. Phase 0 has completed successfully, Phase 1 is under way. This paper presents an update on the status of Phase 0.  
 
TUP060 Potential Photochemical Applications of the Free Electron Laser Irradiation Technique in Living Organisms FEL, experiment, electron, laser 505
 
  • F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
    LEBRA, Funabashi, Japan
  • T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  • T. Sakae
    Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan
  
  In 2001, the Laboratory for Electron Beam Research and Application (LEBRA) achieved the first lasing of 0.9–6.5 microns near-infrared free electron lasers (FELs), in which higher harmonics were generated by using nonlinear optical crystals. Following this breakthrough, we have paid considerable attention to LEBRA-FEL’s potential for investigating photochemical reactions in living organisms. We have established a micro-irradiation technique using an optical fiber connected to a fine tapered glass rod of <5 microns in diameter, enabling FEL irradiation of a single cell and even the inner organelles of live cells. We then verified that visible LEBRA-FEL light can control the germination of lettuce seeds, a well-known photochemical reaction, and determined that red light (660 nm FEL) promotes germination and far-red light (740 nm FEL) inhibits it. Here, we summarize the efficiency of various visible wavelengths of LEBRA-FEL light, ranging from 0.4–0.8 microns, for regulating photoreactions in lettuce seeds and we also summarize the efficiency of infrared wavelengths up to 20 microns, which can be generated by combined use of the LEBRA-FEL and the Kyoto University FEL.
We thank the staff of Prof. T. Morii (Institute of Advanced Energy, Kyoto Univ.) for helpful assistance. 		 
 
TUP064 Narrow Linewidth, Chirp-Control and Radiation Extraction Optimization in an Electrostatic Accelerator FEL Oscillator FEL, electron, laser, wiggler 509
 
  • H. S. Marks, A. Gover, H. Kleinman, J. Wolowelsky
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • D. Borodin, M. Einat, M. Kanter, Y. Lasser, Yu. Lurie
    Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
  
  In recent years the electrostatic accelerator FEL based in Ariel has undergone many upgrades. By varying the accelerating potential the resonator allows lasing between 95-110 GHz. It is now possible to remotely control the output reflectivity of the resonator and thereby vary both the power built up in the resonator and that emitted. This has allowed fine control over the power for different user experiments. A voltage ramping device has been installed at the resonator/wiggler to correct drops in voltage which occur due to electrons striking the walls of the beam line. This has allowed stable pulses of just over 50 μs with a chirp rate of ~80 kHz/μs.  
 
TUP066 Facility for Coherent THz and FIR Radiation bunching, FEL, undulator, electron 512
 
  • A. Meseck
    HZB, Berlin, Germany
  • V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  
  Linac based THz sources are increasingly becoming the method of choice for a variety of research fields, justifying the increasing demand for high repetition rate THz FEL facilities world wide. In particular, pump and probe experiments with THz and IR radiation are of major interest for the user community. In this paper, we propose a facility which accommodates an SRF-linac driven cw THz-FEL in combination with an IR undulator which utilizes the microbunched beam. The layout permits almost perfect synchronization between pump and probe pulse as well as nearly independently tunable THz and IR radiation.  
poster icon Poster TUP066 [1.655 MB]  
 
TUP070 Numerical Calculation of Diffraction Loss for Characterisation of a Partial Waveguide FEL Resonator FEL, laser, simulation, electron 521
 
  • Q. Fu, B. Qin, P. Tan, K. Xiong, Y.Q. Xiong
    HUST, Wuhan, People's Republic of China
  
  Waveguide is widely used in long wavelength Free-Electron Lasers to reduce diffraction losses. In this paper the amplitude and phase transverse distribution of light emission produced in a partial-waveguide FEL resonator is calculated by Fresnel principle. To acquire high power out-coupled and optimize resonator structure of HUST THz-FEL, the characterisation of reflecting mirror is discussed to reduce diffraction loss.  
 
TUP074 High Power Coupled FEL Oscillators for the Generation of High Repetition Rate Ultrashort Mid-IR Pulses cavity, FEL, injection, coupling 532
 
  • M. Tecimer
    University of Hawaii at Manoa, Honolulu, USA
  
  100-200 MeV range ERL-FELs generating few cycle short, high intensity mid-IR pulses with tens of MHz repetition rates might become attractive tools in various strong field applications. In a recent study [1] a mode locked coupled FEL oscillator scheme has been presented to produce multi-mJ level, ultra-short (<10 cycles) pulses tunable within the entire IR region. In this work an improved coupled FEL oscillator scheme is described. The coupled system operates unidirectionally (feedback in the reverse direction less than 10-8 level). The various operational regimes of the system are discussed. Some of the conclusions stated in [1] have been revised.
[1] M. Tecimer, PRST-AB 15, 020703 (2012). 		 
 
TUP077 Characteristics of Transported Terahertz-wave Coherent Synchrotron Radiation at LEBRA FEL, electron, synchrotron-radiation, synchrotron 541
 
  • N. Sei, H. Ogawa
    AIST, Tsukuba, Ibaraki, Japan
  • K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
    LEBRA, Funabashi, Japan
  
  Funding: This work has been supported in part under the Visiting Researcher's Program of the Research Reactor Institute, Kyoto University, and ZE Research Program ZE25B-7, Kyoto University.
Nihon University and National Institute of Advanced Industrial Science and Technology have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University since 2011. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator dedicated for an infrared free-electron laser (FEL), and confirmed it to be CSR [*]. Moreover, we have transported the CSR to an experimental room, which is next to the accelerator room across a shield wall, using an infrared FEL beamline. The transported CSR beam can be applied to two-dimensional imaging and spectroscopy experiments. In this presentation, characteristics of the CSR beam and applications for the CSR beam at LEBRA will be reported.
* N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104. 		 
 
TUP079 A Swedish Compact Linac-based THz/X-ray Source at FREIA electron, cavity, gun, linac 545
 
  • V.A. Goryashko
    Private Address, Uppsala, Sweden
  • A. Opanasenko
    NSC/KIPT, Kharkov, Ukraine
  • V. Zhaunerchyk
    University of Gothenburg, Gothenburg, Sweden
  
  THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.  
 
TUP082 Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation electron, laser, undulator, experiment 556
 
  • A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk
    DELTA, Dortmund, Germany
  
  Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented. 		 
 
TUP083 ALPHA – The THz Radiation Source based on AREAL electron, undulator, FEL, emittance 561
 
  • T.L. Vardanyan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, B. Grigoryan, M. Ivanyan, V.G. Khachatryan, V.H. Petrosyan, V. Sahakyan, A. Sargsyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, G.S. Zanyan
    CANDLE SRI, Yerevan, Armenia
  
  Advanced Research Electron Accelerator Laboratory (AREAL) based on photo cathode RF gun is under construction at the CANDLE. The basic aim of this new facility is to generate sub-picosecond duration electron bunches with an extremely small beam emittance and energies up to 50 MeV. One of the promising directions of the facility development is the creation of ALPHA (Amplified Light Pulse for High-end Applications) experimental stations with coherent radiation source in THz region based on the concept of both conventional undulator and novel radiation sources. The status of the AREAL facility, the main features and outlooks for the ALPHA station are presented in this work.  
 
TUP089 The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) Project electron, undulator, FEL, linac 585
 
  • A.A. Aksoy, Ö. Karslı, C. Kaya, O. Yavaş
    Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
  • P. Arıkan
    Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey
  • S. Özkorucuklu
    Istanbul University, Istanbul, Turkey
  
  Funding: Work is supported by Ministry of Development of Turkey with Grand No: DPT2006K-120470
The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) which is proposed as a first facility of Turkish Accelerator Center (TAC) Project will operate two Infra-Red Free Electron Lasers (IR-FEL) covering the range of 3-250 microns. The facility will consist of an injector fed by a thermionic triode gun with two-stage RF bunch compression, two superconducting accelerating modules operating at continuous wave (CW) mode and two independent optical resonator systems with different undulator period lengths. The electron beam will also be used to generate Bremsstrahlung radiation. The facility aims to be first user laboratory in the region of Turkey in which both electromagnetic radiation and particles will be used. In this paper, we discuss design goals of the project and present status and road map of the project. 		 
 
TUP095 Design of a Compact Light Source Accelerator Facility at IUAC, Delhi electron, gun, undulator, laser 596
 
  • S. Ghosh, R.K. Bhandari, G.K. Chaudhari, D. Kanjilal, J. Karmakar, N. Kumar, A. Pandey, P. Patra, A. Rai, B.K. Sahu
    IUAC, New Delhi, India
  • A.S. Aryshev, J. Urakawa
    KEK, Ibaraki, Japan
  • A. Deshpande, T.S. Dixit
    SAMEER, Mumbai, India
  • V. Naik, A. Roy
    VECC, Kolkata, India
  
  Funding: * The project is supported jointly by Board of Research in Nuclear Sciences and Inter University Accelerator Center
The demand for a light source with high brightness and short pulse length from the researchers in the field of physical, chemical, biological and medical sciences is growing in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source at Inter University Accelerator Centre (IUAC) has been taken up. In the first phase of the project, prebunched [1] electron beam of ~ 8 MeV will be produced by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the second phase, the energy of the electron beam will be increased up to 50 MeV by two sets of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper the detailed design of the LSI accelerator complex as well as construction timetable will be presented. The physical principles of THz generation and major accelerator subsystems will be discussed.
[1] S. Liu & J.Urakawa, Proc. of FEL 2011, page-92 		 
 
TUC01 Hard X-ray Self-Seeding Setup and Results at SACLA undulator, electron, FEL, photon 603
 
  • T. Inagaki, N. Adumi, T. Hara, T. Ishikawa, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Goto, Y. Inubushi, T.K. Kameshima, T. Ohata, K. Tono
    JASRI/SPring-8, Hyogo, Japan
  • T. Hasegawa, S. Tanaka
    SES, Hyogo-pref., Japan
  • H. Kimura, A. Miura, H. Ohashi, H. Yamazaki
    Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan
  
  In order to improve the spectral and temporal properties of XFEL, the self-seeding option based on the transmission crystal optics has been implemented in SACLA since 2012. The self-seeding setup composed of four dipole magnets that can generate up to 50 fs temporal delay and a diamond single crystal with the thickness of 180 micro-m has been installed at the position of the 9th undulator segment, which has been moved downstream. In 2013, the installation of all the components has been completed in August and the commissioning has been started in October. After a number of tuning processes such as the beam collimation and undulator K-value optimization, significant spectral narrowing has been confirmed at 10 keV with the C(400) Bragg reflection. The spectral bandwidth of seeded FEL is about 3 eV, which is nearly one order narrower than that of SASE measured without the diamond crystal. The peak spectral intensity of seeded FEL is about 5 times higher than that of SASE. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs. This talk gives the overview of the plan, achieved results and ongoing R&D.  
slides icon Slides TUC01 [20.337 MB]  
 
TUC03 Generation of Optical Orbital Angular Momentum Using a Seeded Free Electron Laser laser, FEL, electron, free-electron-laser 609
 
  • P. Rebernik Ribič, G. De Ninno, D. Gauthier
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  Funding: The research was in part funded by the TALENTS UP Programme (7th R&D Framework Programme, Specific Programme: PEOPLE - Marie Curie Actions - COFUND).
We propose an effective scheme for the generation of intense extreme-ultraviolet light beams carrying orbital angular momentum (OAM). The light is produced by a high-gain harmonic-generation free-electron laser (HGHG FEL), seeded using a laser pulse with a transverse staircase-like phase pattern. The transverse phase modulation in the seed laser is obtained by putting a phase-mask in front of the focusing lens, before the modulator. The staircase-like phase pattern is effectively transferred onto the electron beam in the modulator and the microbunching structure is preserved after frequency up-conversion in the radiator. During light amplification in the radiator, diffraction and mode selection drive the radiation profile towards a dominant OAM mode at saturation. With a seed laser at 260 nm, gigawatt power levels are obtained at wavelengths approaching those of soft x-rays. Compared to other proposed schemes to generate OAM with FELs, our approach is robust, easier to implement, and can be integrated into already existing FEL facilities without extensive modifications of the machine layout. 		 
 
WEA04 First Lasing from a High Power Cylindrical Grating Smith-Purcell Device electron, simulation, experiment, cathode 611
 
  • H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd
    AES, Medford, New York, USA
  • J.T. Donohue
    CENBG, Gradignan, France
  • J. Gardelle, P. Modin
    CEA, LE BARP cedex, France
  
  Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62.
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode. 		 
slides icon Slides WEA04 [2.344 MB]  
 
WEB04 The New IR FEL Facility at the Fritz-Haber-Institut in Berlin FEL, electron, cavity, undulator 629
 
  • W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, A. Paarmann, G. von Helden
    FHI, Berlin, Germany
  • H. Bluem, D. Dowell, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young
    AES, Princeton, New Jersey, USA
  • S.C. Gottschalk
    STI, Washington, USA
  • U. Lehnert, P. Michel, W. Seidel, R. Wünsch
    HZDR, Dresden, Germany
  
  A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures [1,2]. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 μs. Regular user operation started in Nov. 2013 with 6 user stations. Pulsed radiation with up to 100 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 μm. We will describe the FEL design and its performance as determined by IR power, bandwidth, and micro-pulse length measurements. Further, an overview of the new FHI FEL facility and first user results will be given. The latter include, for instance, spectroscopy of bio-molecules (peptides and small proteins) conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase.
[1] W. Schöllkopf et al., MOOB01, Proc. FEL 2012.
[2] W. Schöllkopf et al., WEPSO62, Proc. FEL 2013.
 		 
slides icon Slides WEB04 [12.785 MB]  
 
THA02 Experimental Characterization of FEL Polarization Control with Cross Polarized Undulators polarization, undulator, FEL, controls 644
 
  • E. Ferrari, E. Allaria, G. De Ninno, B. Diviacco, D. Gauthier, L. Giannessi, G. Penco, C. Spezzani
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • J. Buck, M. Ilchen
    XFEL. EU, Hamburg, Germany
  • G. De Ninno, D. Gauthier
    University of Nova Gorica, Nova Gorica, Slovenia
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • Z. Huang, A.A. Lutman
    SLAC, Menlo Park, California, USA
  • G. Lambert, B. Mahieu
    LOA, Palaiseau, France
  • J. Viefhaus
    DESY, Hamburg, Germany
  
  Polarization control of the coherent radiation is becoming an important feature of recent and future short wavelength free electron laser facilities. While polarization tuning can be achieved taking advantage of specially designed undulators, a scheme based on two consecutive undulators emitting orthogonally polarized fields has also been proposed. Developed initially in synchrotron radiation sources, crossed polarized undulator schemes could benefit from the coherent emission that characterize FELs. In this work we report the first detailed experimental characterization of the polarization properties of an FEL operated with crossed polarized undulators in the Soft-X-Rays. Aspects concerning the average degree of polarization and the shot to shot stability are investigated together with a comparison of the performance of various schemes to control and switch the polarization  
slides icon Slides THA02 [5.383 MB]  
 
THB02 Experimental Results of Diagnostics Response for Longitudinal Phase Space diagnostics, electron, laser, free-electron-laser 657
 
  • F. Frei, V.R. Arsov, H. Brands, R. Ischebeck, B. Kalantari, R. Kalt, B. Keil, W. Koprek, F. Löhl, G.L. Orlandi, A. Saá Hernández, T. Schilcher, V. Schlott
    PSI, Villigen PSI, Switzerland
  
  At SwissFEL, electron bunches will be accelerated, shaped, and longitudinally compressed by different radio frequency (RF) structures (S-, C-, and X-band) in combination with magnetic chicanes. In order to meet the envisaged performance, it is planned to regulate the different RF parameters based on the signals from numerous electron beam diagnostics. Here we will present experimental results of the diagnostics response on RF phase and field amplitude variations that were obtained at the SwissFEL Injector Test Facility.  
slides icon Slides THB02 [6.110 MB]  
 
THP014 Cyclotron-Undulator Cooling of a Free-Electron-Laser Beam electron, undulator, cyclotron, FEL 710
 
  • A.V. Savilov, I.V. Bandurkin, S.V. Kuzikov
    IAP/RAS, Nizhny Novgorod, Russia
  
  We propose methods of fast cooling of an electron beam, based on wiggling of particles in an undulator in presence of an axial magnetic field. We use a strong dependence of the axial electron velocity on the oscillatory velocity, when the electron cyclotron frequency is close to the frequency of electron wiggling in the undulator field. Such cooling may open a way for creating a compact X-ray free-electron laser based on the stimulated scattering of a powerful laser pulse on a moderately-relativistic (several MeV) electron beam. This work is supported by the Russian Foundation for Basic Research (Projects 14-08-00803 and 14-02-00691).  
poster icon Poster THP014 [0.166 MB]  
 
THP016 Optimization of FEL Performanceby Dispersion-based Beam-tilt Correction FEL, simulation, electron, lattice 714
 
  • M.W. Guetg, S. Reiche
    PSI, Villigen PSI, Switzerland
  
  In Free Electron Lasers (FEL) the beam quality is of crucial importance for the radiation power. A transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch. This leads to a reduced bunching and decreased FEL performance. The dominant sources of slice misalignments in FELs are the coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression, which is required for one of the key operation modes for the SwissFEL under construction at the Paul Scherrer Institute in Switzerland. The slice centroid shift can be corrected using multi-pole magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane.  
 
THP018 The Seed Laser System for the Proposed VUV FEL Facility at NSRRC laser, FEL, electron, undulator 718
 
  • M.C. Chou, N.Y. Huang, W.K. Lau, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  
  The possibility of establishing a free electron laser facility in Taiwan has been a continuing effort at NSRRC in the past several years. The baseline design of the envisioned NSRRC FEL is a high gain harmonic generation (HGHG) FEL seeded by a 266 nm laser. The seed laser is produced by adding an optical parametric amplification (OPA) system pumped by upgrading the existing IR laser system. To provide broad tunability of the FEL radiation, the seed laser will be tunable. The spectrum considered for seeding the FEL is between 266 - 800 nm with peak power of 200 MW. The spatial and temporal overlap between the sub-100 fs electron bunch and the 100 fs UV seed laser is under study.  
poster icon Poster THP018 [0.152 MB]  
 
THP027 LCLS-II Bunch Compressor Study: 5-Bend Chicane emittance, electron, FEL, wakefield 755
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  
  In this paper, we present a potential design for a bunch compressor consisting of 5 bend magnets which is designed to compensate the transverse emittance growth due to Coherent Synchrotron Radiation (CSR). A specific implementation for the second bunch compressor in the LCLS-II is considered. The design has been optimized using the particle tracking code, ELEGANT. Comparisons of the 5-bend chicane’s performance with that of a symmetric 4-bend chicane are shown for various compression ratios and bunch charges. Additionally, a one-dimensional, longitudinal CSR model for the 5-bend design is developed and its accuracy compared against ELEGANT simulations.  
poster icon Poster THP027 [0.881 MB]  
 
THP031 Further Understanding the LCLS Injector Emittance emittance, electron, collimation, laser 774
 
  • F. Zhou, K.L.F. Bane, Y. Ding, Z. Huang, H. Loos
    SLAC, Menlo Park, California, USA
  
  Funding: US DOE under contract No. DE-AC02-76SF00515
Notable COTR effect from the LCLS laser heater chicane is recently observed at the LCLS injector OTR screen, used for routine emittance measurements. The emittance with the OTR screen is under-estimated by about 30% compared to the values with the wire scanner located next to the OTR screen. The emittance with the OTR and wire scanner is compared and relevant analyses are presented. Slice emittance upstream of the LCLS BC1 is measured using a traditional transverse cavity. Recently, slice emittance downstream of the BC1 is able to be measured with a newly developed technique, using a collimator located in the middle of the BC1. The parasitic effects of using the collimator for slice emittance measurement are evaluated. The slice emittance before and after the BC1 is compared. The dependence of the slice emittance on the linearizer’s transverse offset and CSR effect from the BC1 is discussed. 		 
 
THP083 Coherent Radiation Diagnostics for Longitudinal Bunch Characterization at European XFEL electron, detector, feedback, diagnostics 925
 
  • P. Peier, H. Dinter, C. Gerth
    DESY, Hamburg, Germany
  
  European XFEL comprises a 17.5 GeV linear accelerator for the generation of hard X-rays. Electron bunches from 20 pC to 1 nC will be produced with a length of a few ps in the RF gun and compressed by three orders of magnitude in three bunch compressor (BC) stages. European XFEL is designed to operate at 10 Hz delivering bunch trains with up to 2700 bunches separated by 222 ns. The high intra-bunch train repetition rate offers the unique possibility of stabilizing the machine with an intra-bunch train feedback, which puts in turn very high demand on fast longitudinal diagnostics. Two different systems will be installed in several positions of the machine. Five bunch compression monitors (BCM) will monitor the compression factor of each BC stage and used for intra-bunch train feedbacks. A THz spectrometer will be used to measure parasitically the longitudinal bunch profile after the energy collimator at 17.5 GeV beam energy. We will present concepts for fast longitudinal diagnostic for European XFEL based on coherent radiation, newest developments for high repetition rate measurements and simulations for the feedback capability of the system.  
 
THP092 Transition Radiation of an Electron Bunch and Imprint of Lorentz-Covariance and Temporal-Causality electron, diagnostics, optics, simulation 952
 
  • G.L. Orlandi
    PSI, Villigen PSI, Switzerland
  
  The study of Transition Radiation (TR) of a bunch of N electrons offers a precious insight into the role that Lorentz-covariance and temporal-causality play in an electromagnetic radiative mechanism of a relativistic beam. The contributions of the N single electrons to the radiation field are indeed characterized by emission phases from the metallic surface which are in a causality relation with the temporal sequence of the N particle collisions onto the radiating screen. The Lorentz-covariance characterizing the virtual quanta field of the relativistic charge is also expected to imprint the radiation field and the related energy spectrum. The main aspects of a Lorentz-covariance and temporal-causality consistent formulation of the TR energy spectrum of an electron bunch will be described.