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| WEPSO01 | Free Electron Lasers in 2013 | 486 |
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Funding: This work has been supported by the Office of Naval Research. Thirty-seven years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and discussed. |
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| WEPSO02 | Results and Perspectives on the FEL Seeding Activities at FLASH | 491 |
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In recent years, several methods of free-electron laser (FEL) seeding, such as high-gain harmonic generation (HGHG), self-seeding, or direct FEL amplification of external seed pulses, have proven to generate intense, highly coherent radiation pulses in the extreme ultraviolet (XUV), soft- (SXR) and hard (HXR) X-ray spectral range. At DESY in Hamburg, the FEL facility FLASH is currently being upgraded by a second undulator beamline (FLASH2) which allows for the implementation of various seeding schemes. The development of high repetition-rate, high-power laser systems allows for the production of seed sources which match the bunch-train pattern of FLASH. Furthermore, the FLASH1 beamline arrangement is well suited for testing various seeding schemes including HGHG, EEHG, HHG-seeding, and hybrid schemes. In this contribution, we* give an overview of latest results and planned FEL seeding activities at FLASH.
*Joern Boedewadt on behalf of the FLASH seeding collaboration (DESY, U Hamburg, TU Dortmund, U Uppsala, U Stockholm) |
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| WEPSO04 | The Conceptual Design of CLARA, a Novel FEL Test Facility for Ultra-short Pulse Generation | 496 |
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| The conceptual design of CLARA, a novel FEL test facility focussed on the generation of ultra-short photon pulses with extreme levels of stability and synchronisation is described. The ultimate aim of CLARA is to experimentally demonstrate that sub-coherence length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling them to generate attosecond pulses, thereby extending the science capabilities of these intense light sources. This paper will describe the design of CLARA, pointing out the flexible features that will be incorporated to allow multiple novel FEL schemes to be proven. | ||
| WEPSO05 | Progress of the LUNEX5 Project | 502 |
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| LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region, with a 400 MeV superconducting linear accelerator and a laser wakefield accelerator (LWFA), feeding a single Free Electron Laser line with seeding with High order Harmonic in Gas and Echo Enable Harmonic Generation. After the Conceptual Design Report (CDR), R&D has been launched on specific magnetic elements (cryo-ready 3 m long in-vacuum undulator, a variable strong permanent magnet quadrupoles), on diagnostics (Smith-Purcell, electro-optics). In recent transport studies from a LWFA with more realistic beam parameters (1 % energy spread, 1 μm size and 1 mrad divergence) than the ones taken in the CDR, a longitudinal and transverse manipulation enables to provide theoretical amplification. A test experiment is under preparation. The French scientific community is increasing its participation to the use of operating FELs. | ||
| WEPSO06 | The Test-FEL at MAX-lab: Implementation of the HHG Source and First Results | 507 |
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| The test-FEL at MAX-lab is a development set-up for seeding techniques. After the successful demonstration of coherent harmonic generation from a conventional laser, the new layout now presents a gas target for generation of harmonics. The drive laser will be up-converted and the low harmonics (around 100 nm) will seed the electron beam. The energy modulated electrons will then be bunched in the dispersive section and will radiate in the second undulator. We will detect the second harmonic of the HHG radiation around 50 nm. This experiment has several challenges never tried before: co-propagation of the electron beam and the drive laser, interaction of the electron beam with the gas in the target, no-focusing of the harmonics and no drive laser removal. The commissioning will show if this kind of in-line chamber has advantages with respect to more traditional approaches with optical beam transport. The results are relevant for many facilities that are planning to implement HHG seeding in the near future. | ||
| WEPSO07 | Simulation Studies for an X-ray FEL Based on an Extension of the MAX IV Linac | 510 |
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| It is well known that the few X-ray FELs around the world are severely overbooked by users. Having a medium energy linac, such as the one now being installed at the MAX IV laboratory, it becomes natural to think about slightly increasing the electron energy to drive an X-ray FEL. This development is now included in the long term strategic plan for the MAX IV laboratory. We will present the current FEL studies based on an extension of the MAX IV linac to 5 GeV to reach the Angstrom region. The injector for the MAX IV accelerator complex is also equipped with a photocathode gun, capable of producing low emittance electron beam. The bunch compression and linearization of the beam is taken care by two double achromats. The basic FEL layout would consist of short period undulators with tapering for extracting all the power from the electron beam. Self-seeding is considered as an option for increasing the spectral and intensity stability. | ||
| WEPSO09 | Two-Color Self-seeding and Scanning the Energy of Seeded Beams at LCLS | 514 |
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Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. The Linac Coherent Light Source (LCLS) produces typically SASE FEL pulses with an intensity of up to 5 mJ and at high photon energy a spread of 0.2% (FWHM). Self seeding with a diamond crystal reduces the energy spread by a factor of 10 to 40. The range depends on which Bragg reflection is used, or the special setup of the electron beam like over-compression. The peak intensity level is lower by a factor of about five, giving the seeded beam an advantage of about 2.5 in average intensity over the use of a monochromator with SASE. Some experiments want to scan the photon energy, which requires that the crystal angle be carefully tracked. At certain energies and crystal angles different lines are crossing which allows seeding at two or even three different colors inside the bandwidth of the SASE pulse. Out-off plane lines come in pairs, like [1 -1 1] and [-1 1 1], which can be split by using the yaw angle adjustments of the crystal, allowing a two-color seeding for all energies above 4.83 keV. |
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| WEPSO10 | Increased Stability Requirements for Seeded Beams at LCLS | 518 |
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Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity. |
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| WEPSO11 | Coherent X-Ray Seeding Source for Driving FELs | 522 |
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Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515 The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options. |
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| WEPSO14 | Towards High Frequency Operation with a Multi-Grating Smith-Purcell FEL | 525 |
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Three-dimensional simulations and experiments have shown that, for a grating equipped with sidewalls, copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave is possible 1, 2. Since the underlying theory is scale invariant, the wavelength emitted is reduced in proportion to a uniform rescaling of the grating. In order to increase our 5 GHz to 100 GHz , the grating surface would be reduced by a factor of 400, which would lead to greatly reduced power. In addition, the required beam might be hard to generate. To avoid this, we propose to use several gratings in parallel with no overall reduction in the total width and the same beam as in our microwave experiment. For this scheme to succeed, it is essential that the bunching in the different gratings be coherent. . Simulations suggest that this occurs for as much as a ten-fold scale reduction. To test this idea, an experiment is using several gratings is being performed.
1. J. T. Donohue and J. Gardelle, Appl. Phys. Lett. 99, 161112 (2011). 2. J. Gardelle, P. Modin and J.T. Donohue, Appl. Phys. Lett. 100, 131103 (2012),. |
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| WEPSO17 | High-resolution Seeding Monochromator Design for NGLS | 529 |
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Funding: DOE/BES A high-resolution soft X-ray seeding monochromator has been designed for self-seeding the Next-Generation Light Source (NGLS). The seeding monochromator system consists of a single variable-line-spacing grating, three mirrors and an exit slit and operates in the “fixed-focus” mode to achieve complete tuning of the seeding energy in range from 200 to 2000 eV with a nearly constant resolving power of over 2x104. The optical delay is less than 1 ps. The design is based upon a fully coherent treatment of the SASE FEL beam propagating from the upstream SASE undulator through the entire seeding monochromator system. This approach guides the design optimization in order to preserve the transverse beam profile entering the seeding undulator to ensure maximum efficiency. |
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| WEPSO19 | A Full Beam 1D Simulation Code for Modeling Hybrid HGHG/EEHG Seeding Schemes for Evaluating the Dependence of Bunching Factor Bandwidth on Multiple Parameters | 533 |
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| Multiple seeding schemes are available for design of narrow-band, short-wavelength FELs. Analysis of such schemes often focus on the amplitude of the final bunching factor b, and how far it is above shot noise. Only under ideal conditions is the bandwidth of b FT limited. We have developed a 1D simulation tool that models complex hybrid seeding schemes using macro properties of the entire beam bunch to assess effects on both the amplitude and bandwidth of b. In particular the effects on bunching factor from using non-ideal beam driven radiators for downstream modulators, energy slew and curvature, and energy spread are investigated with the 1D tool. | ||
| WEPSO20 | Wake Monochromator in Asymmetric and Symmetric Bragg and Laue Geometry for Self-seeding the European X-ray FEL | 538 |
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| We discuss the use of self-seeding schemes with wake monochromators to produce TW power, fully coherent pulses for applications at the dedicated bio-imaging bealine at the European X-ray FEL, a concept for an upgrade of the facility beyond the baseline previously proposed by the authors. We exploit the asymmetric and symmetric Bragg and Laue reflections (σ polarization) in diamond crystal. Optimization of the bio-imaging beamline is performed with extensive start-to-end simulations, which also take into account effects such as the spatio-temporal coupling caused by the wake monochromator. The spatial shift is maximal in the range for small Bragg angles. A geometry with Bragg angles close to pi/2 would be a more advantageous option from this viewpoint, albeit with decrease of the spectral tunability. We show that it will be possible to cover the photon energy range from 3 keV to 13 keV by using four different planes of the same crystal with one rotational degree of freedom. | ||
| WEPSO22 | FERMI@Elettra Status Report | 546 |
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Funding: Work supported in part by the Italian Ministry of University and Research under grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3 In this paper we report about the status of FERMI, the seeded Free Electron Laser located at the Elettra laboratory in Trieste, Italy. The facility welcomed the first external users on FEL-1 between December 2012 and March 2013, operating at wavelengths between 65 and 20 nm. Variable polarization and tunability of the radiation wavelength were widely used. Photon energies attained up to 200 microJoule, depending on the grade of spectral purity requested and on the selected wavelength. Pump-probe experiments were performed, both by double FEL pulses obtained via double pulse seeding of the electron beam and by providing part of the seed laser to the experimental stations as user laser. The FEL-2 line, covering the lower wavelength range between 20 and 4 nm thanks to a double stage cascaded HGHG scheme, operating in the "fresh bunch injection” mode, generated its first coherent photons in October 2012 and has seen further progress during the commissioning phases in 2013, at higher electron beam energy. In fact we will also report on the linac energy increase to 1.5 GeV and on the repetition rate upgrade from 10 to 50 Hz and eventually comment on the FEL operability and uptime. |
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| WEPSO24 | Compact XFEL Light Source | 757 |
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Funding: This work was supported by DARPA grant N66001-11-1-4192, CFEL DESY, DOE grants DE-FG02-10ER46745, and NSF grant DMR-1042342. X-ray free electron laser studies are presented that rely on a nanostructured electron beam interacting with a “laser undulator” configured in the head-on inverse Compton scattering geometry. The structure in the electron beam is created by a nanoengineered cathode that produces a transversely modulated electron beam. Electron optics demagnify the modulation period and then an emittance exchange line translates the modulation to the longitudinal direction resulting in coherent bunching at x-ray wavelength. The predicted output radiation at 1 keV from a 7 MeV electron beam reaches 10 nJ or 6X108 photons per shot and is fully coherent in all dimensions, a result of the dominant mode growth transversely and the longitudinal coherence imposed by the electron beam nanostructure. This output is several orders of magnitude higher than incoherent inverse Compton scattering and occupies a much smaller phase space volume, reaching peak brilliance of 1027 and average brilliance of 1017 photons/(mm2 mrad2 0.1% sec). |
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| WEPSO26 | Status of the Flash Facility | 550 |
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| The free-electron laser user facility FLASH at DESY (Hamburg, Germany)finished its 4th user period in February 2013. In total 2715 hours of SASE radiation has been delivered to user experiments with photon wavelengths between 4.2 nm and 44 nm with up to 5000 photon pulses per second. After a shutdown to connect the second undulator line - FLASH2 - to the FLASH linac, and a following commissioning period, FLASH is scheduled to continue user operation in October 2013. The year 2014 will be dedicated to the 5th period of user experiments. The commissioning of FLASH2 will take place in 2014 parallel to FLASH1 user operation. | ||
| WEPSO27 | Recent LCLS Performance From 250 to 500 eV | 554 |
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Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES. The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV. [1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho- ton. 4(9), 641–647 (2010). |
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| WEPSO28 | Fast Electron Beam and FEL Diagnostics at the ALICE IR-FEL at Daresbury Laboratory | 557 |
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| The ALICE facility at Daresbury Laboratory is an energy recovery based infra-red free electron laser of the oscillator type that has been operational since 2010. Recently fast diagnostics have been installed to perform combined measurements on pulse-by pulse FEL pulse energy and bunch-by-bunch electron bunch position and arrival time. These measurements have highlighted and quantified fast instabilities in the electron beam and consequently the FEL output, and are presented and discussed here. | ||
| WEPSO30 | Integrating the FHI-FEL Into the FHI Research Environment - Design and Implementation Aspects | 562 |
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The new mid-infrared FEL at the Fritz-Haber-Institut (FHI) was presented at the FEL12 conference*. It will be used for spectroscopic investigations of molecules, clusters, nanoparticles and surfaces. This facility must be easy to use by the scientists at FHI, and should be seamlessly integrated into the existing research environment. The Experimental Physics and Industrial Control System (EPICS) software framework was chosen to build the FHI-FEL control system, and will also be used to interface the user systems. The graphical operator interface is based on the Control System Studio (CSS) package. It covers radiation safety monitoring as well as controlling the complete set of building automation and utility devices, regardless of their particular function. A user interface (subset of the operator interface) allows user-provided experiment-control software (KouDa, LabVIEW, Matlab) to connect with an EPICS Gateway providing secured access. The EPICS Channel Archiver continuously records selected process variable data and provides a web server offering archive and near real-time data. A sample experiment installation demonstrates how this user interface can be used efficiently.
* W. Schöllkopf et al., FIRST LASING OF THE IR FEL AT THE FRITZ-HABER-INSTITUT, BERLIN, Conference FEL12 |
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| WEPSO31 | THz Radiation Source Potential of the R&D ERL at BNL | 566 |
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Funding: Work supported by BSA DOE, Contract No. DE-AC02-98CH10886 An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under commissioning at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL will be used as a test bed to study issues relevant for very high current ERLs. High repetition rate (9.5 MHz), CW operation and high performance of electron beam with some additional components make this ERL an excellent driver for high power coherent THz radiation source*. We discuss potential use of BNL ERL as a source of THz radiation and results of the beam dynamics simulation. We present the status and commissioning progress of the ERL. *Ilan Ben-Zvi. et al. Coherent harmonic generation of THz radiation using wakefield bunching (presented at this conference) |
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| WEPSO33 | Remote RF Synchronization With Femtosecond Drift at PAL | 570 |
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Funding: This research was supported by the PAL-XFEL Project, South Korea. We present our recent progress in remote RF synchronization using an optical way at PAL. A 79.33-MHz, low-jitter fiber laser is used as an optical master oscillator (OMO), which is locked to the 2.856-GHz RF master oscillator (RMO) using a balanced optical-microwave phase detector (BOM-PD). The locked optical pulse train is then transferred via a timing-stabilized 610-m long optical fiber link. The output is locked to the 2.856 GHz voltage controlled oscillator (VCO) using the second BOM-PD, which results in remote synchronization between the RMO and the VCO. We measured the long-term phase drift between the input optical pulse train and the remote RF signals using an out-of-loop BOM-PD, which results in 2.7 fs (rms) drift maintained over 7 hours. We are currently working to measure the phase drift between the two RF signals and reduce the phase drift over longer measurement time. |
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| WEPSO34 | Proposal for a Scheme to Generate a 10 tw Power Level, Femtosecond X-ray Pulses for Bio-imaging of Single Protein Molecules at the European XFEL | 574 |
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| Crucial parameters for bio-imaging experiments are photon energy range, peak power and pulse duration. For a fixed resolution, the largest diffraction signals are achieved at the longest wavelength supporting that resolution. In order to perform these experiments at the European XFEL, we propose to use a novel configuration combining self-seeding and undulator tapering techniques with the emittance-spoiler method. Experiments at the LCLS confirmed the feasibility of these three techniques. Their combination allows obtaining a dramatic increase the XFEL output peak power and a shortening of the photon pulse duration to levels sufficient for performing bio-imaging of single protein molecules at the optimal photon-energy range between 3 keV and 5 keV. We show here that it is possible to achieve up to a 100-fold increase in peak-power of the X-ray pulses at the European XFEL: the X-ray beam would be delivered in 10 fs-long pulses with 50 mJ energy each at a photon energy around 4 keV. We confirm by simulations that one can achieve diffraction before destruction with a resolution of 0.25 nm resolution. | ||
| WEPSO37 | Femtosecond Fiber Timing Distribution System for the Linac Coherent Light Source | 583 |
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Funding: This work is supported by Department of Energy under STTR grant DE-C0004702. We present the design and progress of a femtosecond fiber timing distribution system for the Linac Coherent Light Source (LCLS) at SLAC to enable the machine diagnostic at the 10 fs level. The LCLS at the SLAC is the world’s first hard x-ray free-electron laser (FEL) with unprecedented peak brightness and pulse duration. The time-resolved optical/x-ray pump-probe experiments on this facility open the era of exploring the ultrafast dynamics of atoms, molecules, proteins, and condensed matter. However, the temporal resolution of current experiments is limited by the time jitter between the optical and x-ray pulses. Recently, sub-25 fs rms jitter is achieved from an x-ray/optical cross-correlator at the LCLS, and external seeding is expected to reduce the intrinsic timing jitter, which would enable full synchronization of the optical and x-ray pulses with sub-10 fs precision. Of such a technique, synchronization between seed and pump lasers would be implemented. Preliminary test results of the major components for a 4 link system will be presented. Currently, the system is geared towards diagnostics to study the various sources of jitter at the LCLS. *P. Emma et al.,Nat. Photonics 4,641-647(2010). *J. Kim et al.,Opt. Lett,, 31,3659(2006). *J. Kim et al.,Opt. Lett,, 32,1044(2007). *J.Kim et al.,Nat. Photonics 2,733-736(2008). |
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| WEPSO41 | Feasibility Studies for Echo-enabled Harmonic Generation on CLARA | 588 |
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| The Compact Linear Accelerator for Research and Applications (CLARA) is a proposed single-pass FEL test facility, designed to facilitate experimental studies of advanced FEL techniques applicable to the next generation of light source facilities. One such scheme under consideration is Echo-Enabled Harmonic Generation (EEHG). In this paper we explore the suitability of CLARA for carrying out studies of this scheme, combining analytical and numerical calculations to determine likely hardware operating ranges, parameters tolerances and estimated FEL performance. A possible adaptation to convert EEHG into a short-pulse scheme is also considered. | ||
| WEPSO43 | EEHG and Femtoslicing at DELTA | 594 |
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| The ultrashort-pulse facility at DELTA (a 1.5-GeV synchrotron light source operated by the TU Dortmund University) based on the coherent harmonic generation (CHG) technique will be upgraded using echo-enabled harmonic generation (EEHG) in order to reach shorter wavelengths. A laser-induced energy modulation is employed in the CHG and EEHG schemes to create a periodic electron density modulation, but can also be used to generate ultrashort pulses of incoherent radiation at arbitrary wavelengths by transversely displacing the off-energy electrons(femtoslicing). A new storage-ring lattice for DELTA will be presented that not only offers enough free straight sections for an EEHG and femtoslicing setup, but also allows to operate both radiation sources simultaneously. | ||
| WEPSO44 | Design Studies for FLUTE, A Linac-based Source of Terahertz Radiation | 598 |
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| FLUTE is a linac-based THz source with nominal beam energy of 40-50 MeV which is presently under construction at KIT. It will be operated in a wide bunch charge range and will use different electron bunch compression schemes. The source will also study different mechanisms of radiation generation and serve as a test facility for related accelerator technology. This contribution presents the results of an overall optimization of the accelerator and a bunch compressor. A usage of a dispersive compressor and a velocity buncher, as well as combination of both are discussed. It is shown that bunch lengths in the range of a few femtoseconds can be achieved at very low bunch charges, while nC-bunches can be compressed down to approximately 200 fs. The utilization of both schemes results in high THz radiation fields at the experimental port. | ||
| WEPSO46 | Study on the fluctuation of electron beam position in KU-FEL | 602 |
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Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power.
[1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009) |
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| WEPSO47 | Simulation Results of Self-seeding Scheme in PAL-XFEL | 606 |
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| There are two major undulator lines in Pohang Accelerator Laboratory XFEL (PAL XFEL), soft X-ray and hard X-ray. For the hard X-ray undulator line, self-seeding is the most promising approach to supply narrow bandwidth radiation to the users. The electron energy at hard X-ray undulator is 10 GeV and the central wavelength is 0.1 nm. We plan to provide the self-seeding option in the Phase I operation of PAL-XFEL. In this talk, the simulation results for the self-seeding scheme of hard X-ray undulator line in PAL XFEL will be presented. | ||
| WEPSO48 | Simulation Studies of FELs for a Next Generation Light Source | 609 |
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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 No. DE-AC02-05CH11231. Several possible FEL beamlines for a Next Generation Light Source are studied. These beamlines collectively cover a wide range of photon energies and pulse lengths. Microbunching and transverse offsets within the electron beam, generated through the linac, have the potential to significantly impact the longitudinal and transverse coherence of the x-ray pulses. We evaluate these effects and set tolerances on beam properties required to obtain the desired properties of the x-ray pulses. |
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| WEPSO50 | FLASH2 Beamline and Phontondiagnostics Concepts | 614 |
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| The FLASH II project will upgrade the soft X-ray free electron laser FLASH at DESY into a multi-beamline FEL user facility with the addition of a second undulator line FLASH2. The present FLASH linear accelerator will drive both undulator lines and FLASH2 will be equipped with variable-gap undulators to be able to deliver two largely independent wavelengths to user endstations at FLASH1 and FLASH2 simultaneously. A new experimental hall will offer space for up to seven user endstations, some of which will be installed permanently. The beamline system will be set up to cover a wide wavelength range with up to three beamlines capable of delivering the 5th harmonic at 0.8 nm and a fundamental in the water window while others will cover the longer wavelengths of 6 - 40 nm and beyond. Photon diagnostics have been developed for many years at FLASH and are in routine operation. Online measurements of intensity, position, wavelength, wavefront, and pulse length are optimized as well as photon beam manipulation tools such as a gas absorber and filters. Civil construction and installations of FLASH II are on-going and first beam is expected for early 2014. | ||
| WEPSO51 | Self-seeding Design for SwissFEL | 618 |
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| The SwissFEL facility, planned at the Paul Scherrer Institute, will provide SASE and self-seeded FEL radiation at a hard (1-7 Å) and soft (7-70 Å) X-ray FEL beamlines. This paper presents the current status of the self-seeding design for SwissFEL. The layout and full 6D start-to-end simulation results are presented for the hard X-ray beamline. Studies for different charges and optimization of the first and second undulator stages are shown. | ||
| WEPSO53 | Harmonic Lasing at the LCLS | 623 |
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Funding: Department of Energy The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system. *B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006) **E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012) |
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| WEPSO56 | Optical Design and Time-dependent Wavefront Propagation Simulation for a Hard X-Ray Split- and delay-unit for the European XFEL | 627 |
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| For the European XFEL an x-ray split- and delay-unit (SDU) is built covering photon energies from 5 keV up to 20 keV. This SDU will enable time-resolved x-ray pump / x-ray probe experiments as well as sequential diffractive imaging on a femtosecond to picosecond time scale. The wavefront of the x-ray FEL pulses will be split by an edge of a silicon mirror coated with Mo/B4C and W/B4C multilayers. Both partial beams will then pass variable delay lines. For different wavelengths the angle of incidence onto the multilayer mirrors will be adjusted in order to match the Bragg condition. Hence, maximum delays between ± 2.5 ps at hν = 20 keV and up to ± 33 ps at hν = 5 keV will be possible. The time-dependent wave-optics simulations have been done with SRW software, for the fundamental and the 3rd harmonic. The XFEL radiation was simulated both in the Gaussian approximation as well as using an output of time-dependent SASE code FAST. Main features of the optical layout, including diffraction on the splitter edge, and optics imperfections were taken into account. Impact of these effects on the possibility to characterize spatial-temporal properties of FEL pulses are analyzed. | ||
| WEPSO57 | Optimization of a Dedicated Bio-imaging Beamline at the European X-ray Fel | 632 |
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| We recently proposed a basic concept for design and layout of a dedicated undulator source for bio-imaging experiments at the European XFEL. Here we present an optimization of that concept. The core of the scheme is composed by soft and hard X-ray self-seeding setups. Using an improved design for both monochromators it is possible to increase the design electron energy up to 17.5 GeV in photon energy range between 2 keV and 13 keV, which is the most preferable for life science experiments. Operating at such high electron energy one increases the X-ray output peak power. Moreover, 17.5 GeV is the preferred operation energy for SASE1 and SASE2 users. This choice will reduce the interference with other undulator lines. We include a study of the performance of the self-seeding scheme accounting for spatiotemporal coupling caused by the use of a single crystal monochromator. This distortion can be easily suppressed by the right choice of diamond crystal planes. The proposed undulator source yields about the same performance as in the case for a X-ray seed pulse with no coupling. Simulations show that the FEL power reaches 2 TW in the 3 keV - 5 keV photon energy range. | ||
| WEPSO58 | Status Report of the Short-pulse Facility at the Delta Storage Ring | 642 |
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Funding: * Work supported by DFG, BMBF and by the Federal State NRW. At DELTA, a 1.5-GeV synchrotron light source operated by the TU Dortmund university, a short-pulse facility employing the CHG (Coherent Harmonic Generation) principle is in operation. Here, the interaction of an intense, ultrashort laser pulse and electrons in an undulator leads to microbunching of a small fraction of the electrons in the bunch. As a consequence, ultrashort, coherent synchrotron-radiation pulses in the VUV regime are emitted at harmonics of the incident laser wavelength. In addition, coherent THz pulses on the sub-ps timescale are generated. In this paper, the latest improvements of the facility and recent measurements are presented, including investigation of the transverse coherence and detection of the CHG radiation using photoemission spectroscopy in a VUV beamline. |
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| WEPSO59 | A Possible Upgrade of FLASH for Harmonic Lasing Down to 1.3 nm | 646 |
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| We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. We demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 1031 photons/(s mrad2 mm2 0.1% BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation. | ||
| WEPSO60 | A Method for Obtaining High Degree of Circular Polarization at X-ray FELs | 651 |
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| Baseline design of many X-ray FEL undulators assumes a planar configuration which results in a linear polarization of SASE FEL radiation. However, many users experiments would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a helical afterburner, but then one should have an efficient method to suppress linearly polarized background from the main undulator. In this paper we consider a new method for such a suppression which is illustrated with the parameters of the soft X-ray undulator SASE3 of the European X-ray FEL. | ||
| WEPSO62 | The IR and THz Free Electron Laser at the Fritz-Haber-Institut | 657 |
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A mid-infrared oscillator FEL with a design wavelength range from 4 to 50 μm has been commissioned at the Fritz-Haber-Institut in Berlin, Germany, for applications in molecular and cluster spectroscopy as well as surface science. The accelerator consists of a thermionic gridded electron gun, a subharmonic buncher and two S-band standing-wave copper structures. The device was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (< 50 keV-psec) and transverse emittance (< 20 π mm-mrad), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz and a macro pulse length of up to 15 μs. Two isochronous achromatic 180 degree bends deliver the beam to the undulators, only one of which is presently installed, and to the beam dumps. Calculations of the FEL gain and IR-cavity losses predict that lasing will be possible in the wavelength range from less than 4 to more than 50 μm. First lasing was achieved at a wavelength of 16 μm in 2012*. We will describe the FEL system design and performance, provide examples of lasing, and touch on the first anticipated user experiments.
* W. Schöllkopf et al., MOOB01, Proc. FEL 2012. |
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| WEPSO63 | Extension of SASE Bandwidth up to 2 % as a Way to Increase Number of Indexed Images for Protein Structure Determination by Femtosecond X-Ray Nanocrystallography at the European XFEL | 661 |
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| Experiments at the LCLS confirmed the feasibility of femtosecond nanocrystallography for protein structure determination at near-atomic resolution. These experiments rely on X-ray SASE pulses with a few microradians angular spread, and about 0.2 % bandwidth. By indexing individual patterns and then summing all counts in all partial reflections for each index it is possible to extract the square modulus of the structure factor. The number of indexed images and the SASE bandwidth are linked, as an increasing number of Bragg spots per individual image requires an increasing spectral bandwidth. This calls for a few percent SASE bandwidth. Based on start-to-end simulations of the European XFEL baseline, we demonstrate that it is possible to achieve up to a 10-fold increase of the electron energy chirp by strongly compressing a 0.25 nC electron bunch. This allows for data collection with a 2 % SASE bandwidth, a few mJ radiation pulse energy and a few fs-pulse duration, which would increase the efficiency of protein determination at the European XFEL. We prove this concept with simulations of photosystem-I nanocrystals, with a size of about 300 nm. | ||
| WEPSO64 | Grating Monochromator for Soft X-ray Self-seeding the European XFEL | 667 |
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| Self-seeding implementation in the soft X-ray wavelength range involves gratings as dispersive elements. We study a very compact self-seeding scheme with a grating monochromator originally designed at SLAC, which can be straightforwardly installed in the SASE3 undulator beamline at the European XFEL. The design is based on a toroidal VLS grating at a fixed incidence angle, and without entrance slit. It covers the spectral range from 300 eV to 1000 eV. The performance was evaluated using wave optics method vs ray tracing methods. Wave optics analysis takes into account the actual beam wavefront of the radiation from the FEL source, third order aberrations, and errors from optical elements. We show that, without exit slit, the self-seeding scheme gives the same resolving power (about 7000) as with an exit slit. Wave optics is also naturally applicable to calculations of the scheme efficiency, which include the monochromator transmittance and the effect of the mismatching between seed beam and electron beam. Simulations show that the FEL power reaches 1 TW, with a spectral density about two orders of magnitude higher than that for the SASE pulse at saturation. | ||
| WEPSO65 | LEBRA Free Electron Laser as a Radiation Source for Photochemical Reactions in Living Organisms | 675 |
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| The radiation sources commonly used in plant applications are commercially available lamps developed for human lighting applications (fluorescent, metal halide, high-pressure sodium, incandescent, light-emitting diode, and laser diode). In contrast, free-electron lasers (FELs) such as LEBRA-FEL produce high-energy, tunable pulse radiation and thus are promising radiation sources for photochemical research. An advantage of LEBRA-FEL is that the peak intensity ranges from 0.35 to 6.5 microns which are wavelengths coinciding with the absorption peaks of living organisms. Previously, we established a microscopic irradiation technique for delivering visible FEL light to single cells through a tapered glass rod (< 10 microns). However, it is still unclear whether LEBRA-FEL can produce sufficient radiant energy at wavelengths effective for triggering photochemical reactions in living organisms. The aim of this study was to evaluate the effectiveness of LEBRA-FEL in lettuce-seed germination tests. Results show promotion by red light and inhibition by far-red light, indicating that LEBRA-FEL can be used to control lettuce-seed germination. | ||
| WEPSO67 | Progress with the FERMI Laser Heater Commissioning | 680 |
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| FERMI@ELETTRA is a seeded free electron laser facility composed by one linac and two FEL lines named FEL-1 and FEL-2. FEL-1 works in HGHG configuration, while FEL2 is a HGHG cascade implementing "fresh bunch" injection into the second stage. Perfomance of FEL-1 and FEL-2 lines have benefited from the use of the laser heater system, which is located right after the injector, at 100 MeV beam energy. Proper tuning of the laser heater parameters has allowed control of the microbunching instability, which is otherwise expected to degrade the high brightness electron beam quality sufficiently to reduce the FEL power. The laser heater was commissioned one year ago and positive effects upon microbunching instabilities and FEL-1 performance was soon observed. In this work we presents further measurements of microbunching suppression in two compressors scheme showing directly the reduction of beam slice energy spread due to laser heater action. We present measuerements showing the impact of the laser heater on FEL2 | ||
| WEPSO68 | Effect of Coulomb Collisions on Echo-enabled Harmonic Generation | 684 |
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Echo Enabled Harmonic Generation (EEHG) for FEL seeding is sensitive to the intrabeam scattering (IBS) effect. The reason for this is that in the process of generation high-harmonic density modulation in the beam the phase space evolves through a stage with narrow energy bands, which are characterized by the energy spread many times smaller than the beam energy spread. Energy diffusion caused by IBS tends to smear our these bands leading to diminished bunching factors at high harmonics. In the previous work [1] IBS in EEHG was studied in a simple model of a drift. This work extends the analysis of [1] to realistic lattices, and is applied to some of the existing practical designs of EEHG seeding.
[1] G. Stupakov, Effect of Coulomb Collisions on Echo-Enabled Harmonic Generation (EEHG), in Proceedings of the 2011 FEL Conference, Shanghai, China, 2011. |
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| WEPSO69 | Optical Cavity Losses Calculation and Optimization of THz FEL with a Waveguide | 689 |
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Funding: the Fundamental Research Funds for the Central Universities，HUST：2012QN080 The optical cavity with waveguide is used in most long wavelength free electron lasers. In this paper, the losses, gains and modes of a terahertz FEL sources in Huazhong Univeristy of Science and Technology(HUST) are analysis. Then the radii of curvature of the optical mirrors and shapes of the waveguide are optimized. |
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| WEPSO70 | Fully Phase Matched High Harmonics Generation in a Hollow Waveguide for Free Electron Laser Seeding | 693 |
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Funding: LASERLAB-EUROPE, grant n◦ 228334 PARIS ERC project (Contract No. 226424) Swiss National Science Foundation under grant PP00P2_128493 A bright high harmonic source is presented delivering up to 1011 photons per second around a central photon energy of 120 eV. Fully phase matched harmonics are generated in an elongated capillary reaching a cut-off energy of 160 eV. The high HHG fluence opens new perspectives towards seeding FELs at shorter wavelengths than the state of the art. Characterization of the phase matching conditions in the capillary is presented. |
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| WEPSO73 | High Average Power Seed Laser Design for High Reprate FELs | 697 |
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Funding: US Department of Energy, under Contract Numbers DE-AC02-0SCH11231. In the proposed Next Generation Light Source (NGLS), FEL designs use lasers to seed the FEL in an HGHG scheme or bunch the electron beam in an E-SASE scheme. The FELs would run at 100kHz to 1MHz, requiring high average power lasers. For the seeded FEL, laser modulation is applied at 200-240nm, with 250-700MW peak power depending on pulse length, which can vary from 100-10fs. The laser consists of a broadband oscillator and amplitude/phase shaper seeding an optical parametric amplifier (OPA). After recompression, the ~800nm pulse is converted to the fourth harmonic. Losses could be high enough to require 250W at 100kHz, making the OPA ~100x more powerful than existing femtosecond OPAs. In the E-SASE scheme, a single cycle of 5 micron light bunches the beam, which then radiates a short X-ray burst. This requires 100% fractional bandwidth, and precise phase control of the e-field within the pulse, as well as broad band compensation of dispersion throughout the laser path. Bandwidth can be increased by splitting the amplified spectrum into segments and coherently recombining. We present design concepts that are expected to meet requirements, and identify R&D needs. |
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| WEPSO78 | Harmonic Lasing Self-seeded FEL | 700 |
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In this paper we perform analysis of capabilities of SASE FELs at the European XFEL for generation of narrow band radiation. An approach based on application of harmonic lasing self-seeding (HLSS) is under study[*]. Effective harmonic lasing occurs in the exponential gain regime in the first part of the undulator, making sure that the fundamental frequency is well below saturation. In the second part of the undulator the value of undulator parameter is reduced such that now the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is defined by the harmonic lasing (i.e. it is reduced by a significant factor depending on harmonic number) but the saturation power is still as high as in the reference case of lasing at the fundamental, i.e. brilliance increases. Application of the undulator tapering in the deep nonlinear regime would allow to generate higher peak powers approaching TW level.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15, 080702 (2012) |
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| WEPSO80 | Coherence Properties of the Radiation From FLASH | 704 |
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| Several user groups at FLASH use higher odd harmonics (3rd and 5th) of the radiation in experiments. Some applications require knowledge of coherence properties of the radiation at he fundamental and higher harmonics. In this paper we presents results of the studies of coherence properties of the radiation from FLASH operating at radiation wavelength of 6.x nm at the fundamental harmonic, and higher odd harmonics (2.x nm and 1.x nm) at electron energy of 1 GeV. | ||
| WEPSO84 | Present Status of Kyoto University Free Electron Laser | 711 |
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A mid-infrared FEL named as KU-FEL (Kyoto University FEL) has been developed for energy related sciences [1]. After the achievement of the first lasing and the power saturation in 2008 [2, 3], we have been working to extend the tunable range of the FEL [4]. By replacing the original 1.6-m undulator into a 1.8 m one, the tunable range was expanded from 10-13 to 5-15 μm in January 2012. Then we fabricated a new undulator duct to reduce the minimum undulator gap from 20 to 15 mm. At 15-mm gap, the FEL gain can be expected to be twice as high as that at 20 mm gap. Commissioning of the new duct will be done in the end of this April. In this presentation, we will report on the result of the commissioning such as tunable range of KU-FEL and the estimated FEL gain, which would be compared with a simulation.
[1] H. Zen, et al., Infrared Phys. Techn., 51, 382 (2008) [2] H. Ohgaki, et al., Proc. of FEL08, 4 (2008) [3] H. Ohgaki, et al., Proc. of FEL2009, 572 (2009) [4] H. Zen, et al., Proc. of FEL2012 |
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| WEPSO88 | High Precision Electronics for Single Pass Applications | 715 |
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| Monitoring and subsequent optimization of electron Linacs and transfer lines requires specific instrumentation for beam position data acquisition and processing. Libera Single Pass E is the newly developed instrument intended for position and charge monitoring in basic and multi-mode operation LINACs. Development, initial measurements and verification of the instrumentation performance were conducted in the Instrumentation Technologies' laboratories, followed by the characterization measurements of the unit carried out at KEK Linac facility. | ||
| WEPSO89 | Design of a Resonator for the CSU THz FEL | 719 |
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Funding: This research is support by Office of Naval Research Global, grant number N62909-10-1-7151 A 6-MeV L-band linac will be used to drive a planar, fixed gap, 2.5-cm period, hybrid undulator with parabolic pole faces. Consequently, this system is capable of generating wavelengths from 160 to 600 μm. In this paper we discuss the design of an optical resonator for this system. The resonator uses hole-coupled mirrors to allow for a straight electron beam line. The Rayleigh length, the position of the waist of the cold-cavity mode and the hole radii will be investigated to optimize the performance of the FEL. |
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