Advanced Concepts & Techniques
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TUP038 Experiments in Electron Beam Nanopatterning 1
  • C. Zhang, W.S. Graves, L.E. Malin, J. Spence
    Arizona State University, Tempe, USA
  • D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz
    UCLA, Los Angeles, USA
  • R.K. Li, E.A. Nanni, X. Shen, S.P. Weathersby, J. Yang
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by NSF Accelerator Science awards 1632780 and 1415583, NSF BioXFEL STC award 1231306, and DOE contracts DE-AC02-76SF00515 and DE-SC0009914.
We report on experiments in nanopatterning electron beams from a photoinjector as a first step toward a compact XFEL (CXFEL). The nanopatterning is produced by Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer-scale electron density modulations. Multi-slice simulations show that the target can be oriented for a two-beam condition where nearly 80% of the elastically scattered electron beam is diffracted into the 220 Bragg peak. An experiment at the two-beam condition measurement has been carried out at the SLAC UED facility showing this effect with 2.26 MeV electrons. We successfully proved a large portion of the main beam is diffracted into 220 spot by tuning the orientation of the sample. Future plans at UCLA are to observe the nanopatterned beam, and to investigate various grating periods, crystal thicknesses, and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation. The SLAC measurement results will be presented along with design of the UCLA experiments.
TUP039 Electron Beam Requirements for Coherent Electron Cooling FEL System 1
  • G. Wang, Y.C. Jing, V. Litvinenko
    BNL, Upton, Long Island, New York, USA
  • J. Ma
    SBU, Stony Brook, New York, USA
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
In this paper, we present results of our studies in amplification of density modulation induced by co-propagating ions in the FEL section of a Coherent Electron Cooling system, as well its interaction with hadrons. We present a set of requirements for electron beam parameters to satisfy for necessary amplification of the density modulation, while preventing loss of the phase information and saturation.
TUP042 Determination of the Slice Energy Spread of Ultra-Relativistic Electron Beams by Scanning Seeded Coherent Undulator Radiation 1
  • J. Bödewadt, R.W. Aßmann, C. Lechner, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • L.L. Lazzarino, T. Plath, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  Modern high-gain free-electron lasers make use of high-brightness ultra-relativistic electron beams. The uncorrelated energy spread of these beams is upon creation of the beam in the sub-permille range and below the resolution of state-of-the-art diagnostics. One method to determine the slice energy spread is to use an external seed laser to imprint a coherent microbunching structure that gives rise to coherent radiation processes, different radiation sources such as transition radiation, synchrotron radiation, or undulator radiation and others. Here, we present a method and show measurements to determine the slice energy spread using an external seed laser with 266 nm wavelength to produce coherent undulator radiation at higher harmonics. The distribution of these harmonics allows retrieval of the electron beam slice energy spread with high precision.  
Passive Linearization of the Magnetic Bunch Compression Using Self-Induced Field and Without Any Active Higher Harmonic RF Structure  
  • G. Penco, E. Allaria, I. Cudin, S. Di Mitri, D. Gauthier, L. Giannessi, E. Roussel, S. Spampinati, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • S. Bettoni, P. Craievich, E. Ferrari
    PSI, Villigen PSI, Switzerland
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • E. Roussel
    SOLEIL, Gif-sur-Yvette, France
  In linac-driven free-electron lasers, colliders and energy recovery linacs, a common way to compress the electron bunch to kA level is based upon the implementation of a magnetic dispersive element that converts the bunch energy deviation in path-length difference. The non-linearities of such a process are usually compensated by enabling a high harmonic rf structure properly tuned in amplitude and phase. This approach is however not straightforward for foreseen C and X-band linacs. In this work we report the experiment performed on the FERMI linac that has demonstrated the possibility to exploit the longitudinal self-induced field excited by the electron beam itself to passively linearize the compression process without any active higher harmonic rf structure. In this novel configuration, the FERMI electron bunch was compressed up to 700 A as in the nominal case and driven along the FERMI FEL-1 undulators, generating intense extreme-ultraviolet pulses that were provided to users for experiments.  
Generation of Sub-fs X-Ray Pulses at the European XFEL  
  • S. Serkez, G. Geloni, S. Karabekyan, M. Lederer, S.I. Tomin
    XFEL. EU, Schenefeld, Germany
  • G. Feng, V. Kocharyan, E. Saldin, I. Zagorodnov
    DESY, Hamburg, Germany
  • A. Kalaydzhyan
    CFEL, Hamburg, Germany
  Time-resolved studies of free electron lasers are of a great importance. The resulting temporal resolution of the user measurements is determined by FEL pulse duration. Here we investigate possibilities to obtain sub-fs-long pulses at the European XFEL. Installation of the drive laser, modulator and magnetic chicane before the baseline undulator is required.  
poster icon Poster TUP044 [0.680 MB]  
TUP045 Interference-Based Ultrafast Polarization Control at Free Electron Lasers 1
  • S. Serkez, G. Geloni
    XFEL. EU, Schenefeld, Germany
  • E. Saldin
    DESY, Hamburg, Germany
  We present a scheme to generate two distinct FEL pulses with different polarization properties and down to 50 fs-order temporal separation. The scheme is based on installation of two consecutive helical undulators, a corrugated structure and emittance spoiler on top of a baseline variable gap undulator, and is exemplified on the SASE3 beamline of the European XFEL. Good temporal coherence by either self or external seeding is preferable. Our schemes can be used for pump-probe experiments and in combination with the "twin-bunch" technique.  
poster icon Poster TUP045 [0.568 MB]  
Ultrafast Electron Diffraction Facility Based on an RF Photogun and Achromatic 90-degree Bends for Sub-100-Femtosecond Timing Jitter  
  • Y.U. Jeong, S. Bae, I.H. Baek, B.A. Gudkov, B. Han, K.H. Jang, H.W. Kim, M.H. Kim, Y.-C. Kim, K. Lee, S.V. Miginsky, J. Mun, J.H. Nam, S. Park, S. Setiniyaz
    KAERI, Daejon, Republic of Korea
  • R. Fabian, H. Ihee, J. Kim, K.Y. Oang, H. Yang
    KAIST, Daejeon, Republic of Korea
  • J.H. Han
    PAL, Pohang, Kyungbuk, Republic of Korea
  • H.W. Kim
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • K.W. Kim
    Chung Buk National University, Cheongju, Republic of Korea
  • S.V. Miginsky, N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • S. H. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
  • S. Park
    Kyungpook National University, Daegu, Republic of Korea
  We have developed a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. This system includes an S-band radio-frequency (RF) photogun and four achromatic bends for compressing electron bunches. Two of them are for ultrafast electron diffraction (UED) experiments on solid and gas samples. The electron bunch duration at the UED beamlines was designed to be ~30 fs in rms. Our target value of the timing jitter between the pumping laser pulse and probing electron bunch is approximately 10 fs. The synchronization between the pumping laser oscillator and a master oscillator of the RF system was successfully performed with the extremely low timing fluctuation of ~10 fs during 24-hour operation*. We developed a high-intense terahertz pumping source with field strength of more than 0.5 MV/cm for THz-pump and electron-probe experiments. We are conducting three independent application experiments with superconducting and strongly-correlated materials and gas samples for ultrafast molecular dynamics.
* H. Yang et al., "10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources," Scientific Reports, 7, 39966, 2017.
A Linac-Based All-in-One THz-Pump and X-Ray-Probe Sources  
  • S. Setiniyaz, I.H. Baek, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S. H. Park
    KAERI, Daejon, Republic of Korea
  • N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  We describe a compact THz-pump and X-ray-probe beamline, based on an electron linac, for ultrafast time-resolved diffraction applications. Two high-energy electron (γ>50) bunches, 5 ns apart, impinge upon a single-foil or a multifoil radiator and generate THz radiation and X-rays simultaneously. The THz pulse from the first bunch is synchronized to the X-ray beam of the second bunch by using an adjustable optical delay of THz pulse. The peak power of THz radiation from the multifoil radiator is estimated to be 0.18 GW for a 200 pC well-optimized electron bunch. The optimization of radiator for X-ray generation, performed by using GEANT4, shows that carbon foils, with a total thickness of 0.5 - 1.0 mm, has the highest yield of 10 - 20 keV hard X-rays for a 25 MeV beam, which is approximately a few 103 photons/(pC electrons) within a few degrees of the polar angle. A carbon multifoil radiator with 35 foils (25 μm thick each) can generate close to 103 hard X-rays/(keV energy bin)/(pC electrons) within a 2° acceptance angle. The longitudinal time profile of X-ray pulse ranges from a few tens to hundreds of fs depending on the acceptance angle.  
Automatic Tuning of the Electron Beam Parameters to Enhance LCLS FEL Performance Using ES  
  • P.M. Anisimov, A. Malyzhenkov, A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  We report on the design of the new automatic fine tuning system for the electron beam parameters using extremum seeking (ES) to enhance LCLS FEL performance. ES is the fastest multidimensional optimization algorithm for finding extremum. First, we demonstrate ES capability to find optimum Twiss parameters of the electron beam and FODO lattice delivering maximum radiation power in Genesis simulations. Then, we use ES for taper optimization and compare the optimum performance with no taper configuration but optimum Twiss parameters. Moreover, we combine these two techniques together for fine tuning to enhance FEL performance even further. Finally, we propose applying ES for fine tuning at LCLS experimentally: Once FEL is tuned to operate at desirable user parameters, electron beam parameters are changed to maximize radiation power, while the last one remains above the lowest border specified by user during each step of the optimization.  
An Optically Levitated Imaging System for X-Ray Free Electron Lasers  
  • A. Malyzhenkov, J.H. Bartlett, A. Castro, V. Lebedev
    LANL, Los Alamos, New Mexico, USA
  We propose an optically levitated imaging system for X-ray Free Electron Lasers. First, we report on the design of an in-vacuo optical levitation trap compatible with X-ray Free Electron Laser vacuum requirements and other technical conditions at the existing Free Electron laser facilities (LCLS, Spring-8, European XFEL, etc). Second, we propose to use this trap for holding a nano/micro particle which will serve as a lens for focusing the X-ray beam on a target. Such a lens can be accurately positioned with respect to the target and, moreover, the relative distance can be varied in time by the user to change optical properties of the X-ray beam on the sample. In particular, we discuss potential materials that can serve as an x-ray propagation media effectively yet also be trapped by optical tweezers. Finally, we discuss the possibility of holding the target in a separate optical trap which would allow target manipulation (position and orientation in space) relative to the X-ray beam and an X-ray detector.  
TUP050 Beam Driven Acceleration and RF Breakdown in Photonic Band Gap Travelling Wave Accelerator Structure 1
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  We report the results of an experiment to demonstrate excitation of wakefields and wakefield acceleration in a photonic band gap (PBG) accelerating structure. The experiment was conducted at the Argonne Wakefield Accelerator (AWA) facility. For modern X-ray free electron lasers (FELs), preservation of the electron beam quality during the beam acceleration is of crucial importance. Therefore, new accelerating structures must be designed with careful attention paid to the suppression of wakefields. PBG structures are widely studied due to their ability to exclude higher order modes. A 16-cell travelling-wave normal conducting PBG structure operating at 11.700 GHz is installed at the AWA beam line. We passed a high-charge single bunch or multiple bunch train through the structure that generated wakefields and evaluated the effect of these wakefields on a low-charge witness beam. We also passed high-charge multiple bunch trains through the structure that generated up to 100 MV/m accelerating gradient and studied the RF breakdown.  
Reaching High Peak Power X-Ray Radiation in Fels  
  • N.A. Yampolsky, D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
  Funding: This work has been supported by LANL LDRD Programm.
The output power in free electron lasers (FELs) such as MaRIE can be achieved through temporal compression of the output pulse. Such a compression can be achieved with conventional gratings in soft x-ray regime or Bragg crystals in hard x-ray regime. Currently, the use of compressing optics is limited due to high radiation fluences and the damage it causes to the grating. We investigate the possibility of reducing the local x-ray fluence at the grating through streaking the pulse transversely and designing optics which compress the streaked pulse. The streaking of the optical pulse can be achieved through streaking of the driving electron beam with a set of transverse deflecting cavities. The optical pulse shape mirrors the shape of the electron beam resulting in the streaked x-ray beam.
Demonstration of Cascaded Pre-Bunching for Complete Trapping of a Relativistic Electron Beam in a Strongly Tapered Undulator  
  • N.S. Sudar, I.I. Gadjev, P. Musumeci, Y. Sakai
    UCLA, Los Angeles, USA
  • M. Babzien, M.G. Fedurin, M.A. Palmer, I. Pogorelsky, M.N. Polyanskiy, C. Swinson
    BNL, Upton, Long Island, New York, USA
  Funding: US DOE Office of High Energy Physics DE-SC0009914 US Dept. of Homeland Security Grant 2014-DN-077-ARI084-01 US DOE Office of Science SCGSR Graduate Student Research Fellowship
We present results of an experiment recently performed at the Brookhaven National Lab's Accelerator Test Facility showing the first successful demonstration of a cascaded pre-bunching scheme. Two modulator-chicane pre-bunchers arranged in series and a high-power CO2 laser seed manipulate the longitudinal phase space of a 52-MeV electron beam, increasing the fraction of electrons initially trapped in the stable accelerating potential of a seeded, strongly tapered undulator interaction from 25% to 95%, accelerating up to 80% of the particles to the final design energy. These results represent an important step in the development of high efficiency tapered undulator interactions, both as advanced accelerators and as high peak and average power coherent radiation sources.
TUP053 The ACHIP Experimental Chambers at PSI 1
  • E. Ferrari, M. Bednarzik, S. Bettoni, S. Borrelli, H.-H. Braun, M. Calvi, Ch. David, M.M. Dehler, F. Frei, T. Garvey, V. Guzenko, N. Hiller, R. Ischebeck, C. Ozkan Loch, E. Prat, J. Raabe, S. Reiche, L. Rivkin, A. Romann, B. Sarafinov, V. Schlott, S. Susmita
    PSI, Villigen PSI, Switzerland
  • E. Ferrari, L. Rivkin
    EPFL, Lausanne, Switzerland
  • P. Hommelhoff
    University of Erlangen-Nuremberg, Erlangen, Germany
  • J.C. McNeur
    Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
  Funding: Gordon and Betty Moore Foundation
The Accelerator on a Chip International Program (ACHIP) is an international collaboration, funded by the Gordon and Betty Moore Foundation, whose goal is to demonstrate that a laser-driven accelerator on a chip can be integrated to fully build an accelerator based on dielectric structures. PSI will provide access to the high brightness electron beam of SwissFEL to test structures, approaches and methods towards achieving the final goal of the project. In this contribution, we will describe the two interaction chambers installed on SwissFEL to perform the proof-of-principle experiments. In particular, we will present the positioning system for the samples, the magnets needed to focus the beam to sub-micrometer dimensions and the diagnostics to measure beam properties at the interaction point.
TUP054 Preparations for Installation of the Double Emittance-Exchange Beamline at the Argonne Wakefield Accelerator Facility 1
  • G. Ha
    PAL, Pohang, Republic of Korea
  • M.E. Conde, D.S. Doran, W. Gai, J.G. Power
    ANL, Argonne, Illinois, USA
  Funding: This work is supported by Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Preparations to upgrade the single EEX beamline at the Argonne Wakefield Accelerator (AWA) facility to a double EEX beamline are underway. The single EEX beamline recently demonstrated exchange-based longitudinal bunch shaping (LBS) which has numerous applications including high-energy physics linear colliders, x-ray FELs, and intense radiation sources. The exchange-based method can generate arbitrary LBS in the ideal case but has limitations in the real case. The double EEX beamline was proposed as a means to overcome the limitations of single EEX due to transverse jitter and large horizontal emittance. In this paper, we present the current status of beamline design and installation and simulation results for the planned experiments: collinear wakefield acceleration with tailored beams and tunable bunch compression without the double-horn feature.
Multi-Staged Enhanced SASE for Sub-Femtosecond, Terawatt Pulses  
  • J.P. MacArthur
    SLAC, Menlo Park, California, USA
  The peak power of an x-ray pulse from the LCLS is limited by saturation effects to a few tens of gigawatts. However, users looking at two-photon processes that scale with the square of the power need higher-power photon pulses. We investigate enhanced SASE for the production of high-power, sub-femtosecond pulses. This scheme can be used in a cascaded manner with the recently developed fresh-slice scheme to reach terawatt power levels.  
Generation of Two-Color X-Ray Free-Electron Lasers Using a Matching-Based Fresh-Slice Method  
  • W. Qin, Y.-C. Chao, Y. Ding, A.A. Lutman
    SLAC, Menlo Park, California, USA
  Two-color high intensity X-ray free-electron lasers (FELs) provide powerful tools for probing ultrafast dynamic systems. A novel concept of realizing fresh-slice two-color lasing through slice-dependent transverse mismatch has been proposed by one of the authors.* In this paper we present a feasible example following this concept based on the Linac Coherent Light Source parameters. Time-dependent mismatch along the bunch is generated by a passive dechirper module and controlled by downstream matching sections, enabling FEL lasing at different wavelengths with a split undulator configuration. Simulations for soft X-ray FELs show that tens of gigawatts pulses with femtosecond duration can be generated.
* Y. Chao, SLAC Report No. SLAC-PUB-16935, 2016.
Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter  
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  • W. Liu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • W. Qin, T.O. Raubenheimer, J. Wu, C. Yang
    SLAC, Menlo Park, California, USA
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.
TUP058 Slippage-Enhanced SASE FEL 1
  • J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.-S. Kang, G. Kim, I.H. Nam
    PAL, Pohang, Kyungbuk, Republic of Korea
  • B. Yang
    University of Texas at Arlington, Arlington, USA
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
TUP059 Alternative Electron Beam Slicing Methods for CLARA and X-ray FELs 1
  • D.J. Dunning, H.M. Castaneda Cortes, S.P. Jamison, T.A. Mansfield, N. Thompson, D.A. Walsh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Bultrini, S.P. Jamison, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • D. Bultrini
    University of Glasgow, Glasgow, Scotland, United Kingdom
  Methods to generate ultra-short radiation pulses from X-ray FELs commonly slice a relatively long electron bunch to feature one (or more) short regions of higher beam quality which then lase preferentially. The slotted foil approach spoils the emittance of all but a short region, while laser-based alternatives modulate the electron beam energy, improving potential synchronisation to external sources. The CLARA FEL test facility under development in the UK will operate at 100-400 nm, aiming to demonstrate FEL schemes applicable at X-ray wavelengths. We present new laser-based slicing schemes which may better suit the wavelength range of CLARA and provide options for X-ray facilities.  
Study of the Electron Transport in the COXINEL FEL Beamline Using a Laser-Plasma Accelerated Electron Beam  
  • T. André, I.A. Andriyash, F. Blache, F. Bouvet, F. Briquez, M.-E. Couprie, Y. Dietrich, J.P. Duval, M. El Ajjouri, A.M. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitegi, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, P. N'gotta, P. Rommeluère, E. Roussel, M. Sebdaoui, K.T. Tavakoli, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
  • S. Bielawski, C. Evain, C. Szwaj
    PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
  • S. Corde, J. Gautier, G. Lambert, B. Mahieu, V. Malka, K. Ta Phuoc, C. Thaury
    LOA, Palaiseau, France
  The ERC Advanced Grant COXINEL aims at demonstrating free electron laser (FEL) at 200 nm, based on a laser-plasma accelerator (LPA). To achieve the FEL amplification a transport line was designed to manipulate the beam properties. The 10 m long COXINEL line comprises a first triplet of permanent-magnet variable-strength quadrupoles (QUAPEVA), which handles the large divergence of LPA electrons, a magnetic chicane, which reduces the slice energy spread, and finally a set of electromagnetic quadrupoles, which provides a chromatic focusing in a 2-m undulator. Electrons were successfully transported through the line from LPA with ionization-assisted self-injection (broad energy spectra up to~250 MeV, few-milliradian divergence).  
TUP062 Electromagnetic and Mechanical Analysis of a 14 mm 10-period NbTi Superconducting Undulator 1
  • F. Trillaud, G.A. Barraza Montiel
    UNAM, Cuernavaca, Morelos, Mexico
  • M. Gehlot, G. Mishra
    Devi Ahilya University, Indore, India
  Funding: DGAPA of UNAM, fund PAPIIT TA100617 SERB, India
A 14 mm - 10 period NbTi superconducting undulator for the next generation of Free Electron Laser has been stud- ied. The optimum electromagnetic pre-design was carried out using RADIA, an extension module of the commercial software Mathematica. For this pre-design, a variable gap was considered. Additionally, a thermo-mechanical study of one eighth of the superconducting undulator was conducted. This study utilized a thermal and mechanical contact model between the pancake coils and the carbon steel core. This coupled model allowed estimating the minimum pre-loading of the coil. This pre-loading ensures that the coil would remain stuck to its pole during cooling. Numerical results are presented for both studies.
* M. Gehlot et al., Nucl. Inst. and Meth. in Phys. Res., Sec. A, Vol. 846, p. 13-17, 2017.
** B.J.A. Shepherd et al., Proceedings of IPAC2014, WEPRI095, 2014.
*** J. Grimmer, R. Kmak, PAC 2005.
poster icon Poster TUP062 [1.355 MB]  
Laser-Plasma Accelerator Based Single-Cycle Attosecond Pulse Generation  
  • Z. Tibai, G. Almasi, J. Hebling, M.I. Mechler, A. Nagyvaradi
    University of Pecs, Pécs, Hungary
  • J.A. Fülöp, Gy. Tóth
    MTA-PTE High-Field Terahertz Research Group, Pecs, Hungary
  • A. Sharma
    ELI-ALPS, Szeged, Hungary
  A carrier-envelope-phase controlled single-cycle attosecond pulse source was proposed by us relying on a conventional linear accelerator.* Here, we demonstrate the feasibility of a related scheme, where a laser-plasma accelerator, rather than a LINAC is used. Pulses from a TW/PW-power laser are focused into a gas jet to generate a relativistic electron beam, which is then sent through a first quadrupole triplet to reduce its divergence. The reduction of the slice energy spread can be accomplished by a first chicane. The electron beam passes through a modulator undulator along with a TW laser beam (ELI-ALPS SYLOS).** Here, the interaction between the electrons, the magnetic field of the undulator, and the electromagnetic field of the laser introduces a periodic energy modulation. The electrons propagate through a second chicane which leads to the formation of a train of nanobunches. The nanobunched electron beam then moves through the radiator undulator consisting of a few periods and creates CEP-stable attosecond pulses According to our calculations, at 60 nm (100 nm) wavelength CEP stable pulses with 13 nJ (22 nJ) energy and 240 as (400 as) duration can be achieved at K=0.8.
* Z. Tibai et al., Phys. Rev. Lett. 113, 104801 (2014).
** online at for ELI-ALPS (The Scientific Case of ELI-ALPS (2015)).
TUP065 Dielectric Laser Acceleration Setup Design, Grating Manufacturing and Investigations Into Laser Induced RF Cavity Breakdowns 1
  • M. Hamberg, D.S. Dancila, M. Jacewicz, J. Ögren
    Uppsala University, Uppsala, Sweden
  • M. Karlsson, A. Rydberg, E. Vargas Catalan
    Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
  • M. Kuittinen, I. Vartiainen
    UEF, Joensuu, Finland
  Funding: Work supported by Stockholm-Uppsala Centre for Free Electron Research.
Dielectric laser acceleration (DLA) is the technique utilizing strong electric fields in lasers to accelerate electrons in the proximity of nanoscaled dielectric gratings. The concept was recently demonstrated in experimental studies. Here we describe the experimental DLA investigation setup design including laser system and scanning electron microscope (SEM). We also present the grating manufacturing methods as well investigations into vacuum breakdowns occurring at RF accelerating structures.
TUP066 Luminosity Increase in Laser-Compton Scattering by Crab Crossing 1
  • Y. Koshiba
    Waseda University, Tokyo, Japan
  • T. Higashiguchi
    Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
  • S. Ota, T. Takahashi, M. Washio
    RISE, Tokyo, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  Funding: Research Fellow of Japan Society for the Promotion of Science
Laser-Compton Scattering X-ray (LCS-X) sources have been expected as compact and powerful sources, beyond X-ray tubes. They will enable laboratories and companies, opening new X-ray science. It is well known that luminosity depends on the collision angle of a laser and electron beam. Head-on collision is ideal in the point of maximizing the luminosity, though it is difficult to create such a system especially with an optical enhancement cavity for a laser. In collider experiments, however, crab crossing is a promising way to increase the luminosity. We are planning to apply crab crossing to LCS to achieve a higher luminosity leading to a more intense X-ray source. Electron beams will be tilted to half of the collision angle using an RF-deflector. Although crab crossing in Laser-Compton scattering has been already proposed, it has not been demonstrated yet anywhere.* The goal of this study is to experimentally prove the luminosity increase by adopting crab crossing. In this conference, we will report about our compact accelerator system at Waseda University, laser system favorable for crab crossing LCS, and expected results of crab crossing LCS.
* V. Alessandro, et al., "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
Study on Cherenkov Laser Oscillator Using Tilted Electron Bunches  
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • M. Brameld, Y. Tadenuma, M. Washio, R. Yanagisawa
    Waseda University, Tokyo, Japan
  • R. Kuroda, Y. Taira
    AIST, Tsukuba, Ibaraki, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  Funding: This work was supported by a research granted from The Murata Science Foundation and JSPS KAKENHI 26286083.
We have been studying a coherent Cherenkov radiation by using tilted electron bunches. Bunch tilting can enhance the radiation power about 10 times due to the wavefront matching of radiations. Recently, we investigated that this technique can produce high peak power THz pulses with sufficient pulse energy. Resulting pulse energy was more than 30 nJ/pulse and peak power was about 10 kW. Introducing the oscillator cavity with two concave mirrors, it would be possible to achieve lasing using tilted electron bunches. In the calculation, 1 uJ/micro-pulse and 100 uJ/macro-pulse broadband THz pulses are expected to be achieved, which are powerful THz sources compared with the existing THz FELs. In this conference, we will report the experimental results of coherent Cherenkov radiation, calculated results toward lasing and future prospectives.
Fresh-Slice X-Ray Free Electron Laser Schemes for Advanced X-Ray Applications  
  • A.A. Lutman, R.N. Coffee, Y. Ding, J.P. Duris, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell, S.P. Moeller, J. Zemella
    SLAC, Menlo Park, California, USA
  • N. Berrah
    University of Connecticut, Storrs, Connecticut, USA
  • C. Emma
    UCLA, Los Angeles, USA
  Funding: This work was supported by Department of Energy contract nos DE-AC02-76SF00515 and DE-SC0012376
The novel fresh-slice XFEL scheme grants control on the temporal slice of the electron bunch lasing in each undulator section. The technique relies on a time-dependent electron bunch trajectory impressed by the transverse wakefield of a corrugated structure and subsequent orbit manipulation in the undulator section. Fully saturated double pulses are produced in two different undulator sections. The wavelength of each pulse is controlled by the undulator magnetic strength and the delay between the pulses can be scanned from a few femtosecond advance of the pulse generated on the bunch head in the second section to a picosecond delay provided by the magnetic chicane. Three-color saturated pulses are demonstrated by using three undulator sections and the polarization of the pulse generated in the last section can be controlled by the variable polarization Delta undulator. In this work we also show the early results for the first multi-stage amplification scheme, producing ultra-short single-pulses with a 100-GW power level in the soft X-rays. The multi-stage amplification is also demonstrated to improve the performance in power and pulse duration control for the two-color FEL scheme.
Using the Optical-Klystron Effect to Increase and Measure the Intrinsic Beam Energy Spread in Free-Electron Laser Facilities  
  • E. Prat, S. Reiche, T. Schietinger
    PSI, Villigen PSI, Switzerland
  • E. Ferrari
    EPFL, Lausanne, Switzerland
  We present a setup based on the optical klystron concept consisting of two undulator modules separated by a magnetic chicane, that addresses two issues in free-electron laser (FEL) facilities. On the one hand, it allows an increase of the intrinsic energy spread of the beam at the source, which is useful to counteract the harmful microbunching instability. This represents an alternative method to the more conventional laser heater with the main advantage that no laser system is required. On the other hand, the setup can be used to reconstruct the initial beam energy spread, whose typical values in FEL injectors around 1 keV are very difficult to measure with standard procedures.  
Towards High-Efficiency Industrial FELs  
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • P. Musumeci
    UCLA, Los Angeles, California, USA
  • S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  • S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A. Zholents
    ANL, Argonne, Illinois, USA
  Funding: DOE Grant No. DE-SC0017102
Free Electron Lasers have achieved prominence as the X-ray light source technology for research applications, but their industrial potential remains largely unexplored, even though FELs could reach wavelength coverage and powers unattainable by active media sources. In response to this challenge, we developed the TESSA (tapering-enhanced stimulated superradiant amplifier) FEL scheme, which enables as much as 50% single-pass beam-to-light energy-conversion efficiency. With strongly tapered helical undulator and stimulated rapid deceleration, TESSA offers an order-of-magnitude improvement over all existing high-efficiency FEL paradigms and beyond the limit of many conventional lasers. The proof-of-concept was recently demonstrated by UCLA in a pilot experiment at 10-μm wavelength, where 35% deceleration efficiency has been achieved in a 50-cm wiggler. The next steps discussed herein, include: the ongoing development of the TESSA high gain amplifier at UV wavelength; a planned transition to SCRF linac driven TESSA oscillator to reach high average powers; and eventually a development of the EUV TESSA oscillator for industrial applications in the semiconductor industry.
slides icon Slides FRA03 [3.313 MB]  
Three-Dimensional Manipulation of the Electron Beam Phase Space for Generating Intense Coherent Radiation in Storage Rings  
  • C. Feng, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • A. Chao
    SLAC, Menlo Park, California, USA
  Several methods have been developed in the last decade to improve the temporal properties of a storage ring based light source. Most of these methods employ external lasers to manipulate the longitudinal phase space of the electron beam to precisely tailor the properties of the radiation pulses. In this work, we show the possibility of the realization of generating fully coherent intense EUV and x-ray radiation pulses via three-dimensional manipulation of the electron beam phase space in storage rings. Theoretical analysis and numerical simulations show that this technique can be used for the generation of megawatt-scale level, fully-temporal coherent EUV and soft x-ray radiation pulses at a storage ring light source.  
European Plasma Accelerator Design Study EuPRAXIA with FEL & HEP User Areas  
  • P.A. Walker
    DESY, Hamburg, Germany
  Funding: Horizon 2020 Programme from European Union
The Horizon 2020 Project EuPRAXIA (European Plasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with a 5 GeV electron beam using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam-driven plasma acceleration approach and will have user areas for FEL user experiments as well as high-energy physics (HEP) detector tests. Other applications such as a compact X-ray source for medical imaging will also be included. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. The contribution will introduce the work up to date, the underlying physics of compact plasma accelerators, and its 16 European partner laboratories and further 22 international associated partners.