FEL2014 - List of Keywords (electron)

Paper	Title	Other Keywords	Page
MOA01	Remembering Samuel Krinsky	FEL, laser, free-electron-laser, experiment	1
	L.-H. Yu BNL, Upton, Long Island, New York, USA
	The presentation recalls the person, life, and achievements of Samuel Krinsky, who passed away this year.
	Slides MOA01 [5.784 MB]

MOA03	First Lasing at FLASH2	undulator, operation, photon, laser	7
	S. Schreiber, B. Faatz DESY, Hamburg, Germany
	FLASH, the free-electron laser user facility at DESY (Hamburg, Germany), has been upgraded with a second undulator beamline FLASH2. The installation of the FLASH2 electron beamline, including twelve variable gap undulators, was finalized early 2014, and beam commissioning of the new beamline started in March 2014. We announce first lasing at FLASH2 achieved at a wavelength of 40 nm on August 20, 2014.
	Slides MOA03 [3.896 MB]

MOB01	Pulse Control in a Free Electron Laser Amplifier	FEL, radiation, laser, undulator	9
	L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy
	Funding: Work supported by MIUR (DM1834 RIC.4-12-2002 and Grants No. FIRB- RBAP045JF2 and No. FIRB-RBAP06AWK3), and by the EU Commission in the Sixth Framework Program, Contract No. 011935- EUROFEL. A significant progress has been made in controlling the properties of the radiation emitted by a FEL amplifier. Experiments have demonstrated the possibility both to increase the temporal coherence and to reduce the amplifier length to reach saturation, by seeding it with an external source. This may be a solid state, short pulse, laser (Ti:Sa,OPA..), doubled or tripled in a crystal, or a high order harmonic pulse generated in gas. The coherence improvement and the increased compactness of the source are only the first beneficial offspring of this marriage between the optical laser world and that of FELs. Non-linear effects in the seeded FEL dynamics may be exploited to shorten the pulse length beyond that allowed by the FEL natural gain bandwidth. Multiple seed pulses can be used to generate pulses whose temporal distance and properties are also controlled. Similarly, the FEL gain can be adapted to match the seed properties by tailoring the electrons phase space to generate ultra-short output pulses at unparalleled intensities. I had the honor (and luck) to participate in many relevant experiments at the SPARC and FERMI FELs and I will give my personal overview.
	Slides MOB01 [29.932 MB]

MOB02	Small-scale Accelerator-based Radiation Sources and Their Applications	FEL, experiment, target, free-electron-laser	14
	Y.U. Jeong KAERI, Daejon, Republic of Korea
	Small-scale accelerator-based radiation sources can be used more widely for developing advanced technologies and exploring new science with high convenience and low cost. Sometimes they are competitive comparing with giant facilities like X-ray free-electron lasers (X-FELs). We have developed a table-top terahertz (THz) FEL for substituting X-ray or millimeter-wave-based security imaging technologies (body scanners) and a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. I will present on the status of the development of the small-scale radiation sources and plans for the pump-probe experiments. Additionally recent research results on biological study with the operating KAERI (Korea Atomic Energy Research Institute) THz FEL will be given.
	Slides MOB02 [32.237 MB]

MOB03	Phase Space Manipulations in Modern Accelerators	laser, FEL, cavity, radiation	16
	D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China under Grants No. 11327902. Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities.
	Slides MOB03 [5.078 MB]

MOP001	Particle Tracking Simulations for EXFEL Complex shape Collimators	radiation, simulation, lattice, photon	22
	V.G. Khachatryan, V.H. Petrosyan, T.L. Vardanyan CANDLE SRI, Yerevan, Armenia
	The study sets the objective to investigate through numerical simulation the produced secondary radiation properties when the electron beam particles hit collimator walls. Using particle tracking simulation code FLUKA, the European XFEL electron beam as well as beam halo interaction with the collimator were simulated. The complex geometrical shape and material composition of the collimator have been taken into account. Absorbed dose spatial distribution in the material of the collimators and particle fluencies from the downstream surface of the collimator were simulated for the total secondary radiation and its main components.

MOP007	High Accuracy Shimming Technique for the Phase Shifters of the European XFEL	undulator, operation, simulation, permanent-magnet	29
	Y. Li DESY, Hamburg, Germany J. Pflüger XFEL. EU, Hamburg, Germany
	For the European XFEL 91 phase shifters are needed, which have to fulfil stringent field integral specifications: There should be no observable beam deflection when the strength, i.e. the magnetic gap is changed In order to facilitate the mass production of 91 phase shifters within the tough XFEL schedule a shimming technique was developed. It is based on measured shim signatures and is straight forward and fast to apply. The method is described and results are presented demonstrating that all requirements can be fulfilled.

MOP012	Implementation Phase of the European XFEL Photon Diagnostics	photon, diagnostics, undulator, FEL	41
	J. Grünert, J. Buck, F. Dietrich, W. Freund, A. Koch, M. Planas XFEL. EU, Hamburg, Germany
	The European XFEL facility with 3 undulators and initially 6 experimental end-stations requires an extensive set of photon beam diagnostics for commissioning and user operation, capable of handling the extreme brilliance and its inherent damage potential, and the high intra bunch train repetition rate of 4.5MHz, potentially causing additional damage by high heat loads and making shot-to-shot diagnostics very demanding [1]. After extensive design [2-4] and prototype studies, in 2014 the installation of the photon beam devices starts with the equipment in the first photon tunnel XTD2 which is where the SASE1 hard X-ray undulator is located. This contribution reports on the device construction progress by focusing on the XTD2 tunnel devices and their implementation into the tunnel environment. [1] J.Grünert, Framework for X-Ray Photon Diagnostics at the European XFEL, TR-2012-003, 04/2012 [2] J.Buck, Online Photoemission Time-of-Flight Spectrometer for X-ray Photon Diagnostics, TR-2012-002, 06/2012 [3] C.Ozkan, Conceptual design report for Imaging Stations at the European XFEL, TR-2012-004, 02/2012 [4] W.Freund, The European XFEL Undulator Commissioning Spectrometer, XFEL. EU 05/2011

MOP014	X-ray Photon Temporal Diagnostics for the European XFEL	photon, diagnostics, brilliance, laser	45
	J. Liu, J. Buck, F. Dietrich, W. Freund, J. Grünert, M. Meyer XFEL. EU, Hamburg, Germany
	European XFEL (XFEL. EU) that will commissioning in 2016 shows great features on its extremely high number of light bullets (27000 p/s) and extremely high average brilliance. The FEL pulses in XFEL. EU are produced in a 10 Hz bunch trains that contains 2700 sub-pulses within the 600 μs time intervals, corresponding to a 220 ns sub-pulse separation and 4.5 MHz repetition rate. Characterizing the temporal properties of the high repetition rate FEL pulses that implicitly different from shot to shot is important for “pump and probe” experiments and data interpretation. Here we report the concept and recent progress about temporal diagnostic for XFEL. EU. THz streaking technique and spectral encoding will be implemented considering the high repetition rate and high brilliance of XFEL. EU. Laser based THz generation, optimization and numerical simulation for streaking FEL electrons with different photon energies will be presented. High repetition rate diagnostic requirements and solutions will also be discussed.

MOP015	A Power Switching Ionization Profile Monitor (3D-IPM)	laser, ion, detector, vacuum	47
	H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu DESY Zeuthen, Zeuthen, Germany
	FLASH at DESY in Hamburg is a linear accelerator to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position and profile changes of the beam. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined evaluation of the horizontal and vertical position as well as the profile. A compact monitor, consisting of two micro-channel plates (MCP) is assembled on a conducting cage along with toggled electric fields in a rectangular vacuum chamber. The particles created by the photon beam, drift in the homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for assessment. This indirect detection scheme operates over a wide dynamic range and allows the live detection of the clear position and the shape of the beam. The final design is presented.
	Poster MOP015 [1.314 MB]

MOP017	Measurement of the Output Power in Millimeter Wave Free Electron Laser using the Electro Optic Sampling Method	laser, FEL, radiation, detector	50
	A. Klein Israeli Free Electron Laser, Ariel, Israel A. Abramovich Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel D. Borodin, A. Friedman Ariel University, Ariel, Israel H. S. Marks University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
	Funding: this work funded in part by Israel Minstry of Defence In this experimental work an electro optic (EO) sampling method was demonstrated as a method to measure the output power of an Electrostatic Accelerator Free Electron Laser (EA-FEL). This 1.4 MeV EA-FEL was designed to operate at the millimeter wavelengths and it utilizes a corrugated waveguide and two Talbot effect quasi-optical reflectors with internal losses of ~30%. Millimeter wave radiation pulses of 10 μs at a frequency of about 100 GHz with peak power values of 1-2 kW were measured using conventional methods with an RF diode. Here we show the employment of an electro-optic sampling method using a ZnTe nonlinear crystal. A special quasi optical design directs the EA-FEL power towards the ZnTe nonlinear crystal, placed in the middle of a cross polarized configuration, coaxially with a polarized HeNe laser beam. The differences in the ZnTe optical axis due to the EA-FEL power affects the power levels of the HeNe laser transmission. This was measured using a polarizer and a balanced amplifier detector. We succeeded in obtaining a signal which corresponds to the theoretical calculation.

MOP018	Conceptual Study of a Self-seeding Scheme at FLASH2	undulator, FEL, simulation, photon	53
	T. Plath, L.L. Lazzarino Uni HH, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355. We present a conceptual study of a self-seeding installation at the new FEL beamline, FLASH2, at the free-electron laser at DESY, Hamburg. For self-seeding, light from a first set of undulators is filtered by a monochromator and thus acts as a seed for the gain process in the main undulator. This scheme has been tested at LCLS at SLAC with a diamond monochromator for hard X-rays and with a grating monochromator for soft X-rays covering energies between 700 and 1000 eV. For such a design to offer benefits at FLASH2, it must be modified to work with X-rays with wavelength of about 5 nm (248 eV) where the damage threshold of the monochromator in the setup and the divergence at longer wavelengths become an issue. An analysis of the potential performance and limitations of this setup is performed using GENESIS 1.3 and a method developed for the soft X-ray self-seeding experiment at the European XFEL. With a total of 9 undulators in the first stage and 8 undulators after the monochromator, a pulse energy contrast ratio of 4.5 was simulated with an initial peak current of 2.5 kA.

MOP022	Pulse by Pulse Electron Beam Distribution for Multi-beamline Operation at SACLA	operation, kicker, septum, linac	71
	T. Hara, T. Inagaki, C. Kondo, Y. Otake, H. Takebe, H. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan K. Fukami JASRI/SPring-8, Hyogo-ken, Japan
	In order to meet the increasing demand for XFEL user operation, the second undulator beamline (BL2) will be installed during the 2014 summer shutdown at SACLA. Following the installation of BL2, a pulse by pulse electron beam distribution system composed of a kicker and a DC twin-septum magnet, which are currently under development, is planned be installed in January 2015. To distribute the electron beam on a bunch-to-bunch basis, the electron beam is deflected into 0 and ±10 mrad directions at 60 Hz by the kicker, and then the DC twin-septum magnet augments the separation angle to ±50 mrad. The kicker magnet is driven by a 60 Hz trapezoidal waveform and stability less than 30 ppm (peak-peak) has been achieved. This pulse by pulse distribution system will be also used for the beam injection to the upgraded low emittance ring of SPring-8 (SPring-8-II) in future. Since the SPring-8-II storage ring has a small dynamic aperture, low emittance is required for the injection beam. Also the beam injection in parallel with the XFEL operation enables to save the running cost of the injector during top-up operation.

MOP028	Field Integral Measurement System and Optical Alignment System for HUST THz-FEL	undulator, FEL, alignment, cavity	80
	B. Qin, Q.S. Chen, M. Fan, Q. Fu, T. Hu, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang HUST, Wuhan, People's Republic of China X. Liu, Z. Ouyang, Y.B. Wang Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China Y.J. Pei USTC/NSRL, Hefei, Anhui, People's Republic of China
	A Free Electron Laser oscillator with radiation wavelength 50–100 μm is under construction in Huazhong University of Science and Technology (HUST). The linear polarization undulator with K=1.0-1.25 has been designed and manufactured by Kyma s.r.l., by using a pure permanent magnet scheme. Acceptance test bas been performed in Kyma factory with well controlled phase error and field integrals for all gaps. This paper introduces the development of an online field integrals measurement system for the undulator, using the stretched wire method. The design and considerations of the optical alignment system is described as well.

MOP036	Estimating Effect of Undulator Field Errors using the Radiation Hodograph Method	undulator, radiation, synchrotron-radiation, free-electron-laser	93
	N.A. Sokolov Budker INP & NSU, Novosibirsk, Russia N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	Spatially-periodic magnetic structures are widely used for generation of high-brilliance radiation in storage rings, sources of synchrotron radiation and free electron lasers. In 1947, V.L. Ginzburg suggested the first undulator scheme. An alternating magnetic field created by a planar undulator makes electrons oscillate in the transverse direction, with interference of radiation emitted from separate parts of the trajectory. The spectrum of the forward emitted radiation is enchanced due to constructive interference. The ondulator is made of the magnetized bars that are not perfect and their magnetization differs. Therefore, the electron trajectory is not purely sinusoidal and, as a result, the spectral intensity fades. The task was to find out if the precision of magnet manufacturing is sufficient. This paper presents modelling of electron motion in the measured magnetic field of the new (third) free electron laser at the Siberian Synchrotron Radiation Centre. We have managed to estimate the effect of the field errors through comparison of the resulting emitted field amplitude with the amplitude from ideal magnet bars using the hodograph method.

MOP037	Modeling and Design of the Variable Period and Pole Number Undulator for the Second Stage of the Novosibirsk FEL	undulator, FEL, simulation, permanent-magnet	96
	I. Davidyuk NSU, Novosibirsk, Russia O.A. Shevchenko, V.G. Tcheskidov, N. Vinokurov BINP SB RAS, Novosibirsk, Russia N. Vinokurov KAERI, Daejon, Republic of Korea
	The concept of the permanent magnet variable period undulator (VPU) has been proposed just several years ago and there are few examples of its implementation yet. The VPUs have several advantages compared to conventional undulators. One of them is wider radiation wavelength tunability range and another one is an option to increase the number of poles for shorter periods. Both these advantages will be realized in VPU which is being developed now at Budker INP. In this paper we present the 2-D and 3-D magnetic field simulation results and discuss the design features of this VPU.

MOP038	Characterization of the Undulator Magnetic Field Quality by the Angle Averaged Radiation Spectrum	undulator, radiation, photon	100
	O.A. Shevchenko, N. Vinokurov BINP SB RAS, Novosibirsk, Russia N. Vinokurov KAERI, Daejon, Republic of Korea
	The real undulator magnetic field always contains errors which influence undulator performance. The effect of these errors is usually characterized by broadening of the spontaneous emission spectrum at zero angle and corresponding reduction of the spectral intensity. This approach works very well for the phase errors while it does not take into account transversal trajectory displacements. The integrated over the angles radiation spectrum contains more complete information about the undulator field quality but its calculation requires more effort. Therefore the spectral density of emitted radiation (the total number of emitted photons with given energy) can be considered as a figure of merit for an undulator. In this paper we derive analytical formula for this spectrum suitable for doing efficient numerical calculations and demonstrate its application to the case of some typical undulator field errors.

MOP039	High Stability Resonant Kicker Development for the SwissFEL Switch Yard	kicker, operation, dipole, linac	103
	M. Paraliev, H.-H. Braun, S. Dordevic, C.H. Gough PSI, Villigen PSI, Switzerland
	The SwissFEL is a linac-based X-ray free electron laser facility under construction at the Paul Scherrer Institute. The facility will provide femtosecond, high brightness X-ray pulses for fundamental and applied science research. To increase facility efficiency, a double bunch operation is planned to serve simultaneously two experimental stations at the full linac repetition rate. The main linac will accelerate two electron bunches spaced 28 ns apart and a fast and stable deflecting system will be used to separate the two bunches into two different undulator lines. The deflecting system uses a novel concept based on resonant kicker magnets. A prototype kicker magnet and its control system were designed and built. Since stability is crucial, the stability performance of the prototype was studied. The peak to peak amplitude stability of ±11 ppm (3.5 ppm rms) was achieved, which is well within the FEL tolerance of ±80 ppm. The layout of the deflecting system and the key design parameters are also presented.

MOP040	General Strategy for the Commissioning of the ARAMIS Undulators with a 3 GeV Electron Beam	undulator, alignment, quadrupole, photon	107
	M. Calvi, M. Aiba, M. Brügger, S. Danner, R. Ganter, R. Ischebeck, L. Patthey, T. Schietinger, T. Schmidt PSI, Villigen PSI, Switzerland
	The commissioning of the first SwissFEL undulator line (Aramis) is planned for the beginning of 2017. Each undulator is equipped with a 5-axis camshaft system to remotely adjust its position in the micrometer range and a gap drive system to set K-values between 0.1 and 1.8. In the following paper the beam-based alignment of the undulator with respect to the golden orbit, the definition of look-up tables for the local correction strategy (minimization of undulator field errors), the fine-tuning of the K-values as well as the setting of the phase shifters are addressed. When applicable both electron beam and light based methods are presented and compared.

MOP041	Summary of the U15 Prototype Magnetic Performance	undulator, vacuum, quadrupole, photon	111
	M. Calvi, M. Aiba, M. Brügger, S. Danner, R. Ganter, C. Ozkan, T. Schmidt PSI, Villigen PSI, Switzerland
	The first undulator prototype (U15) was assembled and magnetically tested. The instrumentation and the algorithms developed for the undulator optimization are presented and a comparison among different approaches is reviewed. The magnetic measurement results before and after the installation of the vacuum components are discussed. The summary of the undulator test with 100 MeV electron beam is presented and the impact of the radiation on the magnetics is addressed.

MOP045	Phase Shifter Design for iSASE	power-supply, undulator, FEL, simulation	123
	S.D. Chen, K. Fang, H.-D. Nuhn, C. Pellegrini, J. Wu, L. Zhu SLAC, Menlo Park, California, USA S.D. Chen, C.-S. Hwang NCTU, Hsinchu, Taiwan K. Fang Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan
	A phase shifter to generate an additional phase advance of the spontaneous light versus the electron beam was de- signed for the iSASE scheme. The iSASE mechanism is for reducing the bandwidth further from SASE FEL process. A large phase advance about 1600*2Pi as the FEL operating at wavelength 0.8 nm was needed according to the simulation of iSASE process. Since the iSASE is thought to implement into LCLS II project, the space limitation causing by LCLS II should be considered when designing the phase shifter. An optimized three-pole electric phase shifter with 7.3 mm gap has the center field of 1.8 T . The vanadium steel was considered as pole material and the magnet physical length is 260 mm, meanwhile the water-cooling type copper coil was adopted. The temperature increment, force analysis, low field operation mode concept, and preliminary tolerance study were discussed.

MOP046	Undulator Radiation Damage Experience at LCLS	undulator, radiation, operation, experiment	127
	H.-D. Nuhn, R.C. Field, Yu.I. Levashov, X.S. Mao, M. Santana-Leitner, J.J. Welch, Z.R. Wolf SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515 The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 μm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.

MOP047	A 200 μm-period Laser-driven Undulator	undulator, laser, plasma, alignment	131
	F. Toufexis, T. Tang, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515 and the DARPA AXiS program. To reduce the linac energy required for a given synchrotron radiation wavelength, and hence the size of the device, a smaller undulator period with sufficient field strength is needed. In this work, a microfabricated, laser-driven undulator with 200um undulator period is proposed. A TE wave that co-propagates with the electron beam is excited between two polysilicon thin films, having a gap of 16.5um. The mode that is excited is a deflecting mode and causes the electron beam to wiggle. The device is fabricated on a silicon wafer, using conventional silicon micromachining techniques. A single polysilicon thin film is supported on a silicon chip, which has a slit from the back to allow delivery of the laser beam. Two such chips are bonded together to form a 16.5um gap, within which the electron beam passes through. The final device has dimensions 1cm x 1cm x 1.1mm and has approximately 35 undulator periods. In this paper, the model, design, fabrication, and cold measurements of the device are reported.

MOP049	Oxygen Scintillation in the LCLS	detector, controls, laser, instrumentation	137
	J.L. Turner, R.C. Field SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 Oxygen is tested as a replacement for Nitrogen in the Gas Detector system in the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center. The attenuation and energy monitors for LCLS use Nitrogen, but for experiments at the Nitrogen K 1S energy of about 410eV this functionality is gone due to energy fluctuations above and below the K-edge. Oxygen was tested as a scintillating gas at 400eV and 8.3keV.

MOP053	SASE FEL Performance at the SwissFEL Injector Test Facility	FEL, undulator, simulation, gun	144
	S. Reiche PSI, Villigen PSI, Switzerland
	A 4 m long prototype of the SwissFEL undulator module with an undulator period length of 15 mm was installed at the SwissFEL Injector Test Facility and tested with a 200 MeV electron beam in the beginning of 2014. We observed FEL lasing in SASE mode in the wavelength range from 70 to 800 nm, tuning the wavelength by energy and gap. The measurements of the FEL performance are reported. on behalf of the SwissFEL Team

MOP054	Harmonic Lasing Options for LCLS-II	undulator, photon, radiation, FEL	148
	G. Marcus, Y. Ding, Z. Huang, T.O. Raubenheimer SLAC, Menlo Park, California, USA G. Penn LBNL, Berkeley, California, USA
	Harmonic lasing can be a cheap and relatively efficient way to extend the photon energy range of a particular FEL beamline. Furthermore, in comparison to nonlinear harmonics, harmonic lasing can provide a beam that is more intense, stable, and narrow-band. This paper explores the application of the harmonic lasing concept at LCLS-II using various combinations of phase shifters and attenuators. In addition, a scheme by which individual undulator modules are tuned to amplify either the third or fifth harmonic in different configurations is presented in detail.

MOP055	Start-to-End Simulations for IR/THz Undulator Radiation at PITZ	radiation, undulator, FEL, simulation	153
	P. Boonpornprasert, M. Khojoyan, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany B. Marchetti, E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany S. Rimjaem Chiang Mai University, Chiang Mai, Thailand
	High brightness electron sources for modern linac-based Free-Electron Lasers (FELs) have been characterized and optimized at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Since the time structure of the electron bunches at PITZ is identical to those at the European XFEL, the PITZ accelerator is being considered as a proper machine for the development of an IR/THz source prototype for pump and probe experiments planned at the European XFEL. Tunable IR/THz radiation sources using synchrotron radiation from a dipole magnet, transition radiation, high gain FELs and coherent radiation of tailored or premodulated beams are currently under consideration. This work describes start-to-end simulations for generating the FEL radiation using an APPLE-II undulator with electron beams produced by the PITZ accelerator. Analysis of the physical parameter space has been performed with tools of the FAST program code package. Electron Beam dynamics simulations were performed by using the ASTRA code, while the GENESIS 1.3 code was used to study the SASE process. The results of these studies are presented and discussed in this paper.

MOP056	SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime	photon, undulator, radiation, FEL	159
	I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany
	The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime.

MOP057	Proposal to Generate 10 TW Level Femtosecond X-ray Pulses from a Baseline Undulator in Conventional SASE Regime at the European XFEL	undulator, laser, free-electron-laser, FEL	164
	E. Saldin, V. Kocharyan, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany G. Geloni XFEL. EU, Hamburg, Germany
	Output characteristics of the European XFEL have been previously studied assuming an operation point at 5 kA peak current. Here we explore the possibility to go well beyond such nominal peak current level. We consider a bunch with 0.25 nC charge, compressed up to a peak current of 45 kA. An advantage of operating at such high peak current is the increase of the x-ray output peak power without any modification to the baseline design. Based on start-to-end simulations, we demonstrate that such high peak current, combined with undulator tapering, allows one to achieve up to a 100-fold increase in a peak power in the conventional SASE regime, compared to the nominal mode of operation. In particular, we find that 10 TW-power level, femtosecond x-ray pulses can be generated in the photon energy range between 3 keV and 5 keV, which is optimal for single biomolecule imaging. Our simulations are based on the exploitation of all the 21 cells foreseen for the SASE3 undulator beamline, and indicate that one can achieve diffraction to the desired resolution with 15 mJ (corresponding to about 3·10¹³ photons) in pulses of about 3 fs, in the case of a 100 nm focus at the photon energy of 3.5 keV.

MOP058	Purified SASE Undulator Configuration to Enhance the Performance of the Soft X-ray Beamline at the European XFEL	undulator, FEL, radiation, laser	169
	V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany
	The purified SASE (pSASE) undulator configuration recently proposed at SLAC promises an increase in the output spectral density of XFELs. In this article we study a straightforward implementation of this configuration for the soft x-ray beamline at the European XFEL. A few undulator cells, resonant at a subharmonic of the FEL radiation, are used in the middle of the exponential regime to amplify the radiation, while simultaneously reducing the FEL bandwidth. Based on start-to-end simulations, we show that with the proposed configuration the spectral density in the photon energy range between 1.3 keV and 3 keV can be enhanced of an order of magnitude compared to the baseline mode of operation. This option can be implemented into the tunable-gap SASE3 baseline undulator without additional hardware, and it is complementary to the self-seeding option with grating monochromator proposed for the same undulator line, which can cover the photon energy range between about 0.26 keV and 1 keV.

MOP059	Beam Dynamic Simulations for Single Spike Radiation with Short-Pulse Injector Laser at FLASH	laser, simulation, operation, radiation	173
	M. Rehders University of Hamburg, Hamburg, Germany J. Rönsch-Schulenburg CFEL, Hamburg, Germany J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany S. Schreiber DESY, Hamburg, Germany
	Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301 This paper discusses the generation of single spike SASE pulses at soft x-ray wavelength at the free-electron laser FLASH by using very short electron bunches of only a few micrometer bunch length. In order to achieve these extremely short bunch lengths, very low bunch charges (in the order of 20 pC) and short electron bunches exiting the photo-injector are required. For this, a new short-pulse injector laser with adjustable rms pulse duration in the range of 0.7 ps to 1.6 ps and bunch charges up to 200 pC was installed, extending the electron beam parameter range before bunch compression in magnetic chicanes. Beam dynamic studies have been performed to optimize the injection and compression of low-charge electron bunches by controlling the effect of coherent synchrotron radiation and space-charge induced bunch lengthening and emittance growth. Optimization includes the pulse parameters of the injector laser. The simulation codes ASTRA, CSRtrack and Genesis 1.3 were employed.

MOP060	Demonstration of SASE Suppression Through a Seeded Microbunching Instability	laser, undulator, FEL, free-electron-laser	177
	C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, E. Hass, K. Honkavaara, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov DESY, Hamburg, Germany K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school 1355. Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.

MOP061	Electron Beam Delays for Improved Temporal Coherence and Short Pulse Generation at SwissFEL	undulator, FEL, radiation, simulation	181
	N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Reiche PSI, Villigen PSI, Switzerland
	Proposals have been made for the introduction of magnetic electron beam delays in between the undulator modules of a long sectional FEL undulator - these can be used for the generation of trains of FEL pulses which can individually be shorter than the FEL cooperation time [] or to greatly improve the temporal coherence of the FEL output compared to the nominal SASE configuration [,,]. This paper comprises a feasibility study of the application of these techniques to the SwissFEL hard X-Ray beamline. Three-dimensional simulations are used to investigate the potential photon output. [] N.R. Thompson and B.W.J. McNeil, PRL 100:203901, 2008. [] N.R. Thompson et al. In Proc IPAC2010, pages 2257–2259, 2010 [*] J. Wu, A. Marinelli, and C. Pellegrini. Proc FEL2012, 2012.

MOP063	A Novel Modeling Approach for Electron Beams in SASE FELs	radiation, FEL, target, operation	190
	P. Niknejadi, J. Madey University of Hawaii, Honolulu,, USA
	We have recently shown that the Wheeler-Feynman analysis of the interaction of a moving charge with distant absorbers [] provides a perfect match to the energy radiated by two coherently oscillating charged particles (a heretofore unsolved problem in classical electrodynamics) []. Here we explain the need to include the Wheeler-Feynman coherent radiation reaction force as an integral part of the solution of the boundary value problem of free electron lasers (FELs) that radiate into “free space”. We will also discuss how the advanced field of the absorber can interact with the radiating particles at the time of emission. Finally we will introduce and explore the possibility of improving the temporal coherence in the self amplified spontaneous emission (SASE) FELs as well as the possibility of optimizing the spectrum of the emitted coherent radiation by SASE FELs via altering the structure of their targets by including the Wheeler-Feynman coherent radiation reaction force in the analysis of FEL operations. Wheeler, J. A.; Feynman, R. P, Rev. Mod. Phys. 17, 157, 1945. ** P. Niknejadi et al. "Energy Conservation of Coherently Oscillating Charged Particles in Classical Electrodynamics" submitted.

MOP065	Optimization of a High Efficiency FEL Amplifier	undulator, FEL, radiation, laser	199
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	The problem of an efficiency increase of an FEL amplifier is now of great practical importance. Technique of undulator tapering in the post-saturation regime is used at the existing x-ray FELs LCLS and SACLA, and is planned for use at the European XFEL, Swiss FEL, and PAL XFEL. There are also discussions on the future of high peak and average power FELs for scientific and industrial applications. In this paper we perform detailed analysis of the tapering strategies for high power seeded FEL amplifiers. Application of similarity techniques allows us to derive universal law of the undulator tapering.

MOP066	An Overview of the Radiation Properties of the European XFEL	radiation, operation, undulator, hardware	204
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	We present an overview of the radiation properties of the European XFEL based on recently accepted strategy of operation at the fixed set of electron energies (8.5 GeV, 12 GeV, 14 GeV, and 17.5 GeV), baseline parameters if the electron beam, and new set undulator parameters. We also discuss potential extension of the parameter space which does not require new hardware and can be realized at a very early stage of the European XFEL operation.

MOP067	Prospects for CW Operation of the European XFEL in Hard X-ray Regime	linac, undulator, operation, FEL	210
	R. Brinkmann, E. Schneidmiller, J.K. Sekutowicz, M.V. Yurkov DESY, Hamburg, Germany
	The European XFEL will operate nominally at 17.5 GeV in SP (short pulse) mode with 0.65 ms long bunch train and 10 Hz repetition rate. A possible upgrade of the linac to CW (continuous wave) or LP (long pulse) modes with a corresponding reduction of electron beam energy is under discussion since many years. Recent successes in the dedicated R&D program allow to forecast a technical feasibility of such an upgrade in the foreseeable future. One of the challenges is to provide sub-Angstroem FEL operation in CW and LP modes. In this paper we perform a preliminary analysis of a possible operation of the European XFEL in the hard X-ray regime in CW and LP modes with the energies of 7 GeV and 10 GeV, respectively. We consider lasing in the baseline XFEL undulator as well as in a new undulator with a reduced period. We show that, with reasonable requirements on electron beam quality, lasing on the fundamental will be possible in sub-Angstroem regime. As an option for generation of brilliant photon beams at short wavelengths we also consider harmonic lasing that has recently attracted a significant attention.

MOP068	Suppression of the Fundamental Frequency for a Successful Harmonic Lasing in SASE FELs	undulator, FEL, simulation, photon	215
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Harmonic lasing in X-ray FELs has recently attracted a significant attention and is now seriously considered as a potential method for generation of brilliant photon beams at short wavelengths. It is clear, however, that for a successful harmonic lasing one has to suppress the fundamental. In this paper we discuss different methods for such a suppression: phase shifters, intraundulator spectral filtering, switching between the 3rd and the 5th harmonics etc.

MOP070	Design Study for the PEHG Experiment at SDUV-FEL	FEL, experiment, bunching, simulation	219
	C. Feng, H.X. Deng, B. Liu, D. Wang, X.T. Wang, M. Zhang, T. Zhang, W. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	Funding: This work was partially supported by National Natural Science Foundation of China (11475250, 11175240 and 11205234) In this paper, design studies for the proof-of-principle experiment of the recently proposed phase-merging enhanced harmonic generation (PEHG) mechanism are presented. A dogleg and a new designed transverse gradient undulator should be added in the undulator system of SDUV-FEL to perform the phase-merging effect. With the help of 3D simulation codes, we show the possible performance of PEHG with the realistic parameters of SDUV-FEL. * H. Deng, C. Feng, Phys. Rev. Lett. 111, 084801. C. Feng, H. Deng, D. Wang, Z. Zhao, New J. Phys.,16, 043021. * C. Feng, T. Zhang, H. Deng, Z. Zhao, Phys. Rev. ST Accel. Beams 17, 070701.

MOP075	Laser Seeding Schemes for Soft X-rays at LCLS-II	undulator, laser, bunching, radiation	223
	G. Penn LBNL, Berkeley, California, USA P. Emma, E. Hemsing, G. Marcus, T.O. Raubenheimer, L. Wang SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515. The initial design for LCLS-II incorporates both SASE and self-seeded configurations. Increased stability and/or coherence than is possible with either configuration may be provided by seeding with external lasers followed by one or more stages of harmonic generation, especially in the soft x-ray regime. External seeding also allows for increased flexibility, for example the ability to quickly vary the pulse duration. Studies of schemes based on high-gain harmonic generation and echo-enabled harmonic generation are presented, including realistic electron distributions based on tracking through the injector and linac.

MOP077	Measurements of the FEL-bandwidth Scaling with Harmonic Number in a HGHG FEL	FEL, laser, operation, experiment	227
	E. Allaria, M.B. Danailov, W.M. Fawley, E. Ferrari, L. Giannessi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Ferrari Università degli Studi di Trieste, Trieste, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy
	In this work we report recent measurements done at FERMI showing the dependence of the FEL bandwidth with respect to the seed laser harmonic at which the FEL is operated. Comparison of FEL spectra for different Fourier-limit seed and chirp pulses is also reported.

MOP078	Measurements of FEL Polarization at FERMI	polarization, FEL, experiment, radiation	231
	E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	We report detailed quantitative characterization of different polarization states of a single-pass, externally-seeded FEL operating with variable polarization undulators in the VUV spectral range. The experiment has been performed at FERMI FEL-1 operated in the 52–26 nm wavelength range. Three different, independent polarimeter setups, installed at the end of ex- perimental beamlines, have been used to characterize the four “pure” polarization states: horizontal, vertical, right-circular and left-circular. The impact of downstream transport optics upon the radia- tion polarization has been assessed; at longer wavelengths, dichroism effects lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other and allow a cross-calibration of the instruments. On behalf of the team organized for polarization measurements at FERMI.

MOP079	Generation of Multiple Coherent Pulses in a Superradiant Free-Electron Laser	FEL, radiation, undulator, simulation	233
	X. Yang, S. Seletskiy BNL, Upton, Long Island, New York, USA L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy
	We analyze the structure of the tail of a superradiant pulse, which is constituted by a train of sub-pulses with decaying amplitudes. We show how a trailing pulse, with pi phase advance from the leading pulse, is generated at the falling edge of the leading superradiant pulse, where the corresponding phase space is deeply saturated and the electrons become de-trapped by the reduced ponderomotive potential. Once the trailing pulse gains enough energy, it generates a second trailing pulse, and the process takes place again. By performing detailed simulations of the resulting electron phase space distribution and the FEL pulse spectral and temporal structure with PERSEO, we confirm that the deformation and re-bunching of the longitudinal phase space create a sequence of pulses. These results are compared to 3D simulations using the FEL code GENESIS 1.3 showing a good agreement.

MOP082	Perspectives for Imaging Single Protein Molecules with the Present Design of the European XFEL	photon, laser, free-electron-laser, FEL	238
	G. Geloni XFEL. EU, Hamburg, Germany V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany O. Yefanov CFEL, Hamburg, Germany
	European XFEL aims to support imaging and structure determination of biological specimens between less than 0.1 microns and 1 micron size with working photon energies between 3 keV and 16 keV. This wide operation range is a cause for challenges to the focusing optics. A long propagation distance of about 900 m between x-ray source and sample leads to a large lateral photon beam size at the optics. Due to the large divergence of nominal X-ray pulses with durations shorter than 10 fs, one suffers diffraction from mirror apertures, leading to a 100-fold decrease in fluence at photon energies around 4 keV, which seem ideal for imaging of single biomolecules. Moreover, the nominal SASE1 is very far from the level required for single particle imaging. Here we show how it may be possible to optimize the SPB instrument for single biomolecule imaging with minimal additional costs and time, achieving diffraction without destruction at near-atomic resolution with 10¹³ photons in a 4 fs pulse at 4 keV photon energy and in a 100 nm focus, corresponding to a fluence of 10²³ ph/cm². This result is exemplified using the RNA Pol II molecule as a case study.

MOP083	Start-to-End Simulation for FLASH2 HGHG Option	simulation, undulator, radiation, FEL	244
	G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov DESY, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany T. Plath Uni HH, Hamburg, Germany
	The Free-electron laser in Hamburg (FLASH) is the first FEL user facility to have produced extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade of FLASH named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections, a seeding undulator section and a SASE undulator section. In this paper, results from a start-to-end simulation for a FLASH2 High-Gain Harmonic Generation (HGHG) option are presented. For the beam dynamics simulation, space charge, coherent synchrotron radiation (CSR) and longitudinal cavity wake field effects are taken into account. In order to get electron beam bunches with small correlated and uncorrelated energy spread, RF parameters of the accelerating modules have been optimized as well as the parameters of the bunch compressors. Radiation simulations for the modulator and the radiator have been done with code Genesis 1.3 by using the particle distribution generated from the beam dynamics simulation. The results show that for a single stage HGHG, 33.6 nm wavelength FEL radiation can be seeded at FLASH2 with a 235 nm seeding laser.

MOP084	Enhancing Coherent Harmonic Generation using Tilted Laser Wavefronts	laser, radiation, synchrotron, synchrotron-radiation	248
	S. Khan DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (contract 05K13PE3) Coherent Harmonic Generation (CHG) to produce ultrashort pulses of synchrotron radiation is based on the interaction of relativistic electrons in a storage ring with femtosecond laser pulses in an undulator. The resulting periodic energy modulation can be converted to a density modulation by a dispersive chicane, giving rise to coherent emission at harmonics of the laser wavelength in a second undulator. If the first undulator is in a section with non-zero dispersion, the density modulation can be enhanced using tilted laser wavefronts, thus delaying the phase-space distributions of electrons with different energy with respect to each other. The most simple way to realize the wavefront tilt would be to introduce a small crossing angle between the electron and laser beam. Details are discussed for the case of the CHG short-pulse facility at DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, but HGHG and EEHG seeding of free-electron lasers could also be performed this way.

MOP086	Broadly Tunable THz FEL Amplifier	FEL, laser, undulator, radiation	252
	C.H. Chen, F.H. Chao, Y.C. Chiu, Y.K. Gan, K.Y. Huang, Y.-C. Huang, Y.C. Wang NTHU, Hsinchu, Taiwan
	Funding: MOST 102-2112-M-007 -002 -MY3, Taiwan In this paper we present a broadly tunable sub-MW THz FEL amplifier driven by a photoinjector with a sub-kW seed THz source tunable between 0.7-2.0 THz. Specifically an S-band photoinjector at 2.856 GHz generate a 3.3-5.5 MeV electron bunch with 0.5 nC charge in a 4.25 ps rms bunch length, which is injected into a 2-m long undulator with a period of 18 mm and an rms undulator parameter of 0.98. The driver laser of the photoinjector is a frequency quadrupled amplified, mode-locked Nd:YVO4 laser at 1064 nm. We recycle the unconverted infrared laser at 1064 nm to pump a THz parametric amplifier using a lithium niobate crystal as its gain crystal. This THz parametric amplifier generates a transform-limited THz pulse with sub-kW power between 0.7 and 2.0 THz, which is seeded into the undulator to produce broadly tunable, transform-limited, sub-MW THz radiation through FEL amplification with a gain of about 3000. Since the pump laser of the THz OPA is derived from the driver laser of the photoinjector, the seed THz pulse is fully synchronized and overlapped with the electron bunch. Experimental progress of this work will be presented in the conference. *Work supported by MoST under NSC 102-2112-M-007-002-MY3
	Poster MOP086 [1.269 MB]

MOP087	Upgrade Plans for the Short-pulse Facility at DELTA	laser, undulator, radiation, dipole	255
	S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW. DELTA is a 1.5-GeV synchrotron light source operated by the TU Dortmund University with a short-pulse facility based on Coherent Harmonic Generation (CHG) * to produce radiation with wavelengths in the VUV regime. Even shorter wavelengths can be generated by an upgrade based on the Echo-Enabled Harmonic Generation (EEHG) technique ** which requires additional magnetic chicanes and undulators. A new storage ring lattice provides enough free space for an EEHG setup and additionally for a femtoslicing undulator. Besides the new optics, first simulation results of EEHG will be presented. * S. Khan et al., Sync. Rad. News 26, 3 (2013). ** G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).

MOP088	High Repetition Rate Energy Modulator System Utilizing a Laser Enhancement Cavity	laser, cavity, radiation, resonance	260
	Y. Honda KEK, Ibaraki, Japan
	A high intensity laser field can be realized at a high repetition rate using an enhancement optical cavity scheme. We propose to apply the 100GW-level laser field inside the cavity for producing a micro-bunch structure in an electron bunch. Combining this system with an ERL scheme of accelerator, it can be used for a seeded FEL at a high repetition rate of ~100MHz continuous beam. The longitudinal electric field at the center area of a higher-order transverse mode of laser can be used to modulate beam energy at a period of the laser wavelength. A 250 MeV class two-loop ERL accelerator has been proposed in KEK as a future upgrade plan of existing 35 MeV ERL test accelerator. It will be able to provide a low emittance, small energy spread, short bunch electron beam at a high repetition rate of continuous operation. We propose to apply this beam to produce a seeded VUV coherent radiation. We will discuss the feasibility of the scheme and status of the laser modulator development.

MOP092	X-ray Monochromators for Self-seeding XFELs in the Photon Energy Range Starting from 1.5 keV	photon, FEL, scattering, radiation	269
	Yu. Shvyd'ko ANL, Argonne, Ilinois, USA
	Self-seeding of XFELs below 1 keV can be performed using grating monochromators [1]. Forward-Bragg diffraction (wake) monochromators [2] were instrumental for achieving self-seeding in hard x-ray FELs in the photon energy range from 5 to 10 keV [3]. Large photo-absorption makes extension into the lower photon range difficult. Here alternative schemes of x-ray monochromators are introduced and discussed for achieving self-seeding in a yet inaccessible spectral range starting from 1.5 keV. [1] J. Feldhaus, et al., Opt. Commun. 140, 341 (1997). [2]. G. Geloni, V. Kocharyan, and E. Saldin, J. Mod. Opt. 58, 1391 (2011). [3] J. Amann, et al., Nat. Photonics 6, 693 (2012).

MOP094	Indirect Measurements of NIR and UV Ultrashort Seed Laser Pulses using a Transverse Deflecting RF-Structure	laser, undulator, experiment, interaction-region	272
	N. Ekanayake, S. Ackermann DESY, Hamburg, Germany S. Ackermann, C. Lechner, Th. Maltezopoulos, T. Plath Uni HH, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany
	Seeding of free-electron lasers (FELs) using external coherent optical pulses recently became an area of interest as users demand spectrally and temporally coherent FEL radiation which is not achievable in traditional self-amplified spontaneous emission operation mode. Since temporal and spectral properties of the seed laser pulses are directly imprinted on the electron bunch, a proper characterization of these seed pulses is needed. However, the lack of any measurement technique capable of characterizing ultrashort seed laser pulses at the laser-electron interaction region is a primary drawback. In this paper we report indirect measurements of seed laser pulses in an undulator section using a transverse deflecting RF-structure (TDS-LOLA) at the free-electron laser FLASH at DESY. Temporally chirped and unchirped seed pulse length measurements will be compared with second-harmonic generation frequency-resolved optical gating measurements and theoretical simulations. Using this technique we will demonstrate that pulse artifacts such as pre- and post-pulses in the seed pulse in the femtosecond and picosecond timescales can be identified without any temporal ambiguity. Authors acknowledge the support received from FLASH team and many groups at DESY in preparation and commissioning of experiments. We thank our colleagues in the FLASH seeding team for their support.

MOP095	HGHG AND EEHG MICROBUNCHES WITH CSR AND LSC	simulation, FEL, dipole, radiation	275
	K.E. Hacker DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (contract 05K13PE3) and DESY Longitudinal space charge (LSC) forces in a drift and coherent synchrotron radiation (CSR) in a chicane are relevant for high gain harmonic generation (HGHG) and echo enabled harmonic generation (EEHG) seeding designs. These factors determine whether or not the modulator can be located significantly upstream of the radiator. The benefits and dangers of having a drift in between the radiator and the modulator are investigated and a measurement of the LSC enabled reduction of the energy spread of a seeded beam is presented.

MOP096	Enhancing the Harmonic Content of an HGHG Microbunch	laser, undulator, simulation, bunching	281
	K.E. Hacker DELTA, Dortmund, Germany
	Funding: BMBF grant 05K10PE1 and DESY High Gain Harmonic Generation (HGHG) seeding has been demonstrated in the visible and ultraviolet, but it is limited in performance at high harmonics of the seed by the initial uncorrelated energy spread of the electron beam. A recent proposal from SINAP using a chirped electron beam and a canted pole undulator has suggested a new mechanism for cooling the uncorrelated energy spread of the electron beam in order to improve the performance of HGHG seeding at high harmonics. This note reviews the mechanism, the limitation of the concept and extrapolates to some new concepts using analogous mechanisms derived from transverse gradients of the laser properties. The impact of CSR wakes on the vanishingly short microbunches produced by the methods are also investigated. [1] H. Deng and C. Feng, Phys. Rev. Lett. 111, 084801 (2013)

MOP097	A Concept for Seeding 4-40 nm FEL Radiation at FLASH2	laser, FEL, bunching, undulator	286
	K.E. Hacker DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (contract 05K13PE3) This note describes a scheme to seed the FLASH2 FEL over a range of 4-40 nm without impacting SASE capabilities. This scheme combines multiple seeding techniques, builds on current infrastructure and offers a maximized range of performance with higher pulse energies than what are available at lower-peak current facilities. The concept relies on Echo Enabled Harmonic Generation (EEHG), cascaded seeding, and Second Harmonic Afterburners (SHAB) while maintaining the possibility to operate with High Gain Harmonic Generation (HGHG) seeding at >30 nm wavelengths.

MOC01	Circular Polarization Control by Reverse Undulator Tapering	FEL, undulator, resonance, bunching	297
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	In order to produce circularly polarized light at X-ray FEL facilities one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. We propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. The method can be used at different X-ray FEL facilities, in particular at LCLS after installation of the helical afterburner in the near future.
	Slides MOC01 [1.545 MB]

MOC03	Radiation Properties of Tapered Hard X-ray Free Electron Lasers	radiation, FEL, undulator, simulation	300
	C. Emma, C. Pellegrini UCLA, Los Angeles, USA S.D. Chen NCTU, Hsinchu, Taiwan K. Fang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S. Serkez DESY, Hamburg, Germany
	We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.
	Slides MOC03 [3.797 MB]

MOC04	Chirped and Modulated Electron Pulse Free Electron Laser Techniques	undulator, radiation, FEL, simulation	303
	J. Henderson, L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom
	Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20 A potential method to improve the free electron laser's output when the electron pulse has a large energy spread is investigate and results presented. A simplified model is the first given, in which there are a number of linearly chirped beamlets equally separated in energy and time. By using chicanes, radiation from one chirped beamlet is passed to the next, helping to negate the effect of the beamlet chirps and maintaining resonant interactions. Hence the addition of chicane allow the electrons to interact with a smaller range of frequencies (Δ ω <2 ρ γ_r), sustaining the FEL interaction. One method to generate such a beamlet structure is presented and is shown to increase FEL performance by two orders of magnitude.
	Slides MOC04 [6.777 MB]

TUA02	A Review of High Power OPCPA Technology for High Repetition Rate Free-Electron Lasers	laser, operation, FEL, free-electron-laser	310
	M.J. Prandolini, R. Riedel HIJ, Jena, Germany M. Schulz DESY, Hamburg, Germany F. Tavella SLAC, Menlo Park, California, USA
	High repetition rate free-electron lasers (FEL) require the development of new laser systems that have the ability to operate at high average power. Optical parametric chirped-pulse amplification (OPCPA) is presently the most promising method to fulfill these requirements. This technique has been used to demonstrate amplification up to tens of watts with a repetition rate in the range between tens of kHz to MHz in burst and continuous mode. We review the current OPCPA technology for systems operating around 800 nm; this includes various frontend options, pump amplifier technology and latests results, and we discuss the important requirements for achieving high power lasers in both burst and continuous operation. Work supported by the Helmholtz Institute Jena and the Deutsches Elektronen-Synchrotron DESY in Hamburg.
	Slides TUA02 [4.997 MB]

TUA04	Status of the SwissFEL C-band Linac	linac, klystron, network, free-electron-laser	322
	F. Löhl, J. Alex, H. Blumer, M. Bopp, H.-H. Braun, A. Citterio, U. Ellenberger, H. Fitze, H. Jöhri, T. Kleeb, L. Paly, J.-Y. Raguin, L. Schulz, R. Zennaro, C. Zumbach PSI, Villigen PSI, Switzerland
	The linear accelerator of SwissFEL will be based on C- band technology. This paper summarizes the latest results that were achieved with the first prototype components. Fur- thermore, the progress and plans of the series production are discussed.
	Slides TUA04 [11.482 MB]

TUB01	Review of Coherent SASE Schemes	undulator, FEL, bunching, experiment	327
	B.W.J. MᶜNeil, L.T. Campbell, J. Henderson USTRAT/SUPA, Glasgow, United Kingdom D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: We acknowledge STFC Agreement No. 4163192; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Julich Supercomputing Centre (JSC), project HHH20 A review is presented of some of the methods and their origins that have recently been proposed to improve the temporal coherence of SASE output. These methods do not require any external laser seed field, or the use of the so-called self-seeding methods, where the SASE radiation is optically filtered and improved at an early stage of the interaction before re-injection and amplification to saturation. By using methods that introduce an additional relative propagation between the electron beam and the radiation field, the localised collective interaction, which leads to the formation of the ‘spiking’ associated with normal SASE output, is removed. The result is output pulses which are close to the fourier transform limit without the need for any external seeds or intermediate optics.
	Slides TUB01 [6.256 MB]

TUB02	Generation of Intense XVUV Pulses with an Optical Klystron Enhanced Self- amplified Spontaneous Emission Free Electron Laser	FEL, klystron, laser, radiation	332
	G. Penco, E. Allaria, G. De Ninno, E. Ferrari, L. Giannessi Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy G. De Ninno University of Nova Gorica, Nova Gorica, Slovenia L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy
	Fermi is a seeded FEL operating in high gain harmonic generation mode. The FEL layout is constituted by a modulator and six radiators separated by a dispersive section. The modulator and the radiators can be tuned to the same resonant frequency to set up an asymmetric optical klystron configuration where self amplified spontaneous emission can be generated and studied. This paper presents the experiment consisting in the analysis of the enhancement of the self-amplified spontaneous emission (SASE) radiation by the dispersion in the optical klystron. The FEL pulses produced with the optical klystron configuration are several order of magnitude more intense than in pure SASE mode with the dispersion set to zero, The experimental observations are in good agreement with simulation results and theoretical expectations. A comparison with the typical high-gain harmonic generation seeded Fel operation is also provided.
	Slides TUB02 [12.835 MB]

TUB03	FEL Overcompression in the LCLS	simulation, experiment, FEL, diagnostics	337
	J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk.
	Slides TUB03 [4.493 MB]

TUB04	Operation of FLASH with Short SASE-FEL Radiation Pulses	laser, FEL, operation, free-electron-laser	342
	J. Rönsch-Schulenburg, E. Hass, N.M. Lockmann, T. Plath, M. Rehders, J. Roßbach Uni HH, Hamburg, Germany G. Brenner, S. Dziarzhytski, T. Golz, H. Schlarb, B. Schmidt, E. Schneidmiller, S. Schreiber, B. Steffen, N. Stojanovic, S. Wunderlich, M.V. Yurkov DESY, Hamburg, Germany
	Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301 This paper describes the experimental activity on the generation of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-electron laser FLASH [1, 2]. The key element, a photo-injector laser which is able to generate laser pulses of about 2 ps FWHM has been optimized and commissioned. It allows the generation of shorter bunches with low bunch charge (of up to 200 pC) directly at the photo-cathode. Initially shorter injector laser pulses and thus shorter bunches eases the required bunch compression factor for short pulses below 10 fs duration which makes operation of the electron beam formation system to be more robust with respect to jitters and collective effects. As a result, overall stability of SASE FEL performance is improved. In the optimal case single-spike operation can be achieved. In this paper the experimental results on production of short electron bunches and the SASE performance using the new injector laser will be shown and the measured electron bunch and FEL radiation properties are discussed. In addition, optimizations of bunch diagnostics for low charge and short bunches are discussed.
	Slides TUB04 [1.201 MB]

TUP002	Characterization of Partially Coherent Ultrashort FEL Pulses	FEL, laser, free-electron-laser, photon	346
	C. Bourassin-Bouchet, M.-E. Couprie SOLEIL, Gif-sur-Yvette, France C. Evain PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
	Temporal metrology is a major need for free-electron lasers. However, the lack of longitudinal coherence, that is shot-to-shot fluctuations, of these sources has prevented so far the full amplitude and phase temporal characterization of FEL pulses. To sort out this issue, we propose a solution inspired from attosecond metrology, where XUV pulse measurement techniques already exist, and from coherent diffraction imaging, where numerical solutions have been developed for processing partially coherent diffraction patterns. The experimental protocole implies the measurement of photoelectron spectra obtained through XUV-laser photoionisation. The spectra are then processed with an algorithm in order to retrieve the partially coherent FEL pulse. When applied to SASE FELs, the technique gives access to the full statistics of the emitted pulses. With seeded-FELs, the pulse shape becomes stable from shot-to-shot, but an XUV-laser time jitter remains. In that case, the technique enables the joint measurement of the FEL pulse shape (in amplitude and phase) and of the laser/FEL jitter envelope. The concept has been validated with numerical simulations in the context of the LUNEX5 FEL project.

TUP003	Quantum FEL II: Many-electron Theory	FEL, laser, resonance, photon	348
	P. Kling, R. Sauerbrey HZDR, Dresden, Germany R. Endrich, E.A. Giese, W.P. Schleich Uni Ulm, Ulm, Germany
	We investigate the emergence of the quantum regime of the FEL when many electrons interact simultaneously with the wiggler and the laser field. We find the Quantum FEL as the limit where only two momentum states are populated by the electrons. Moreover, we obtain exponential gain-per-pass and start-up from vacuum.

TUP004	Quantum FEL I: Multi-mode Theory	photon, resonance, coupling, FEL	353
	R. Endrich, E.A. Giese, W.P. Schleich Uni Ulm, Ulm, Germany P. Kling, R. Sauerbrey HZDR, Dresden, Germany
	The quantum regime of the FEL in a single-mode, single-particle approximation is characterized by a two-level behaviour of the center-of-mass motion of the electrons. We extend this model to include all modes of the radiation field and analyze the effect of spontaneous emission. In particular, we investigate this scattering mechanism to derive experimental conditions for realizing an FEL in the quantum regime.

TUP006	Two-color Free-electron Laser via Two Orthogonal Undulators	FEL, polarization, undulator, radiation	358
	N.S. Mirian IPM, Tehran, Iran G. Dattoli ENEA C.R. Frascati, Frascati (Roma), Italy V. Petrillo Universita' degli Studi di Milano, Milano, Italy
	An amplifier Free electron Laser (FEL) including two orthogonal polarized undulators with different periods and field intensities is able to emit two color radiations with different frequency and polarization while the total length of device does not change respect to usual single color FELs. The wavelengths of two different colors can be changed by choosing different periods, while variation in the magnetic strengths can be used to modify the gain lengths.

TUP007	Spectral Limits and Frequency Sum-rule of Current and Radiation Noise Measurement	radiation, distributed, undulator, FEL	362
	A. Gover, R. Ianconescu University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel A. Nause UCLA, Los Angeles, USA
	Funding: This research was supported by a grant from the United States-Israel Binational Science Foundation(BSF), Jerusalem, ISRAEL The current noise spectrum of an electron beam is generally considered white and expressed by the shot-noise formula (eI0). It is possible to control the spectral energy of a random electron beam current by longitudinal space charge microdynamics and dispersive transport. Both noise suppression (relative to eI0)[1,2] and noise enhancement[3] have been demonstrated, exhibiting sub/super-Poissonian particle distribution statistics, respectively. We present a general theory for the current noise of an e-beam and its radiation emission in the entire spectrum. The measurable current noise spectrum is not white. It is cut-off at high frequencies, limited by the measurement length and the beam axial momentum spread (fundamentally limited by quantum uncertainty). We show that under certain conditions the current noise spectrum satisfies a frequency sum-rule: exhibiting noise enhancement in one part of the spectrum when suppressed at another part and vice versa. The spontaneous emission (radiation noise) into a single radiation mode or single direction in any scheme (OTR, Undulator etc.) is sub-radiant when the beam current is sub-Poissonian and vice versa, but the sum-rule does not apply.

TUP008	An Analysis of Optimum Out-coupling Fraction for Maximum Output Power in Oscillator FEL	coupling, FEL, cavity, laser	368
	Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	The effect of the out-coupling fraction on the output power in oscillator FEL is analyzed. The formulas of the optimum out-coupling fraction and the corresponding maximum output power are given. They are dependent on the initial small signal gain and the passive loss rate of the light in the optical cavity. The initial comparison show that the result given by the formula agree well with the results in references.

TUP009	A Simple Method for Generating a Few Femtosecond Pulses in Seeded FELs	laser, FEL, radiation, linac	371
	H.T. Li, Z.G. He, Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by Major State Basic Research Development Program of China (2011CB808301) and the Fundamental Research Funds for the Central Universities of China (WK2310000045) We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the centre part of electron beam and short pulses in high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse with duration of 8 femtoseconds (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 m.

TUP012	Numerical Simulation of a Super-radiant THz Source Driven by Femtosecond Electron Bunches	undulator, FEL, radiation, emittance	374
	R.V. Chulkov B.I. Stepanov Institute of Physics, Belarus, Russia V.A. Goryashko Uppsala University, Uppsala, Sweden V. Zhaunerchyk University of Gothenburg, Gothenburg, Sweden
	Funding: We would like to acknowledge the financial support from the Swedish FEL center. Pulsed THz FELs are typically driven by rf Linacs which produce intense electron bunches with a duration of a few picoseconds or even shorter. When the bunch duration is less than a picosecond, the wavelength of the THz light is greater than the bunch length and the FEL operates in the super-radiant (SR) regime. In the report, we summarize our studies performed for an SR source operating in the THz frequency range. In particular, we focus on an open-type planar undulator comprising no guiding structure. Using a numerical code that supports 3D modeling of the SR dynamics as well as statistical properties of electron bunches, we analyze influence of electron bunch parameters on generated THz radiation and reveal some surprising results. More specifically, for the considered undulator configuration, we predict degradation in the angular divergence and spectral broadening of the generated radiation as the electron bunch emittance decreases. We also demonstrate how electron bunch broadening associated with the electron energy spread can eventually be suppressed. R. Chulkov, V. Goryashko, and V. Zhaunerchyk, Report III of the series of reports by the Swedish FEL Center and FREIA Group, http://www.diva-portal.org/smash/get/diva2:699684/FULLTEXT01.pdf.
	Poster TUP012 [1.553 MB]

TUP013	X-Ray Smith-Purcell Radiation from a Beam Skimming a Grating Surface	radiation, target, factory, free-electron-laser	378
	D.Yu. Sergeeva, A.A. Tishchenko MEPhI, Moscow, Russia
	Smith-Purcell radiation as a base of Free Electron Lasers is actively studied experimentally and by simulating. Usually the beam is supposed to move at some distance above the target. In practice the distance is tried to decrease so that the beam passes very close to the target surface. Experimental data contains the information about grating heating. The authors of article* suggested the cause of the heating is that the beam skims the grating surface. Developing the method used in,* we give the analytical description of the X-Ray radiation arising when the beam of charge particles moves parallel above the periodical target, but the part of the beam crosses the target. The radiation arising is the superposition of Smith-Purcell radiation and transition radiation from the grating. This radiation determines the process of beam bunching and following gain of radiation. H.L.Andrews et al,Phys. Rev. ST AB 12 (2009) 080703 A.A.Tishchenko, A.P.Potylitsyn, M.N.Strikhanov, Phys. Rev. E 70 (2004) 066501 **D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189

TUP014	Forward X-Ray and Ultraviolet Smith-Purcell Radiation for FEL	radiation, target, polarization, plasma	384
	A.A. Tishchenko, D.Yu. Sergeeva MEPhI, Moscow, Russia
	The scheme of Free Electron Lasers based on Smith-Purcell effect is well known to describe the process of interaction between an electron beam and evanescent wave, which bunches this beam. In this work we concentrate on the process of generation of the radiation propagating at small angles. In terms of approach described in detail in,, we investigate the Smith-Purcell radiation at oblique incidence of a single charged particle for X-Ray and UV frequency region. This forward radiation propagates through all the region of the beam moving and provides more close interaction between the beam and the radiation, than usual surface waves existing in FELs. Spectral and angular characteristics of the forward radiation are discussed from point of view its role in Smith-Purcell based FELs. A.P.Potylitsyn, M.I.Ryazanov, M.N.Strikhanov, A.A.Tishchenko, Diffraction Radiation from Relativistic Particles, Springer, 2011 **D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189

TUP015	Radiation and Interaction of Layers in Quasi-plane Electron Bunches Moving in Undulators	radiation, undulator, laser, free-electron-laser	388
	N. Balal Ariel University, Ariel, Israel V.L. Bratman IAP/RAS, Nizhny Novgorod, Russia
	The model of radiating planes (1D radiating gas) consisting of electrons that oscillate and travel with a relativistic translational velocity allows one to develop a simple general theory describing a number of important effects of radiation in a undulator for dense electron bunches formed in photoinjector accelerators. Having based on this method and taking into account both Coulomb and radiation interactions of the planes with an arbitrary density, particle velocity distribution and energy chirp we have found analytically and numerically efficiency and frequency spectrum for coherent spontaneous radiation, including conditions for generation of minimum narrow and very broadband spectra. The developed theory has been applied for estimation of a powerful terahertz radiation source with a moderate energy of electrons.

TUP016	Quasi-optical Theory of Terahertz Superradiance from an Extended Electron Bunch	radiation, simulation, resonance, wakefield	391
	N.S. Ginzburg, A. Malkin, A. Sergeev, V.Yu. Zaslavsky, I.V. Zotova IAP/RAS, Nizhny Novgorod, Russia
	Funding: This study was supported by the Russian Foundation for Basic Research (project no. 14-08-01180) and the Dynasty Foundation. We consider superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multi-megawatt terahertz pulses. To study the above process we have developed a three-dimensional, self-consistent, quasi-optical theory of Cherenkov stimulated emission which includes a description of the formation of evanescent waves near the corrugated surface and its excitation by RF current induced in the electron bunch. Results obtained in the framework of a quasi-optical model were confirmed by direct CST STUDIO PIC simulations. There is a possibility of advancement towards still shorter wavelengths (infrared and optical), which can be achieved by decreasing the period of the diffraction gratings and increasing the density and energy of the particles in the electron bunches. Increase of coupling impedance can be obtained by using inclined incidence of electron bunch on corrugated surface (clinotron configuration). Ginzburg N.S et al. Phys. Rev. Lett. 2013. V.110, Iss.18. 184801.*

TUP017	Using Lorentz Transformations for Simulations of Wiggler Superradiance from the Picosecond Electron Bunches	undulator, simulation, radiation, scattering	395
	A. Malkin, N.S. Ginzburg, A.A. Golovanov, I.V. Zotova IAP/RAS, Nizhny Novgorod, Russia V.P. Tarakanov LPI, Moscow, Russia
	Funding: This work was supported by Russian Foundation for Basic Research under Grant No 12-02-01152. In this paper we present a theoretical analysis of superradiance (SR) from picosecond electron bunches wiggling in periodical undulator field based both on the method of averaged ponderomotive force and on a direct numerical PIC (particle-in-cell) simulation. Within both approaches the analysis takes place in the reference frame co-moving with electrons which allows simplifying the procedure of simulation significantly due to the fact that all the spatial scales including the radiation wavelength, the length of the beam and the length of the pump field pacet into which the undulator field is transformed are of the same order. We show that in the reference frame the SR effect can be interpreted as a formation of the distributed Bragg mirror in the bulk of the electron beam which is effectively reflecting (scattering) the pump wave. A possibility of generation of multimegawatt pulses in terahertz and far infrared wave ranges is demonstrated.

TUP018	Sensitivity Study of a Tapered Free-Electron Laser	FEL, emittance, undulator, free-electron-laser	399
	A.W.L. Mak, F. Curbis, S. Werin MAX-lab, Lund, Sweden
	The output power of a free-electron laser (FEL) can be greatly enhanced by tapering the undulator line. In this work, a sensitivity study of a tapered FEL is presented. The study is conducted using the numerical simulation code GENESIS and a taper optimization method. Starting from a possible case for the future X-ray FEL at the MAX IV Laboratory in Lund, Sweden, a number of parameters are varied systematically and the impact on the FEL power is investigated. These parameters include the electron beam's initial energy, current, emittance, energy spread, as well as the seed radiation power.

TUP019	Update on the FEL Code Genesis 1.3	undulator, radiation, lattice, FEL	403
	S. Reiche PSI, Villigen PSI, Switzerland
	The widely used time-dependent code Genesis 1.3 has been modified to address new needs of users worldwide. The existing limitation of tracking isolated slices of the FEL beam has been overcome by keeping the entire electron beam in memory, which is tracked as a whole through the undulator. This modification allows for additional features such as allowing particles to migrate into other slices or applying self-consistent wakefield and space charge models.

TUP020	MINERVA, a New Code to Model Free-Electron Lasers	FEL, undulator, experiment, simulation	408
	H. Freund, P.J.M. van der Slot CSU, Fort Collins, Colorado, USA P.J.M. van der Slot Mesa+, Enschede, The Netherlands
	Simulation codes modelling the interaction of electrons with an optical field inside an undulator are an essential tool for understanding and designing free-electron lasers (FELs). As there exists a large variety of FELs ranging from long-wavelength oscillators using partial wave guiding to soft and hard x-ray FELs that are either seeded or starting from noise, a simulation code should be capable of modelling this huge variety of FEL configurations. A new code under development, named MINERVA, will be capable of modelling such a large variety of FELs. The code uses a modal expansion for the optical field, e.g., a Gaussian expansion for free-space propagation, and an expansion in waveguide modes for propagation at long wavelengths, or a combination of the two for partial guiding at THz frequencies. MINERVA uses the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to model oscillators. Here we describe the main features of MINERVA and give various examples of its capabilities.

TUP021	Recent Updates to the Optical Propagation Code OPC	diagnostics, FEL, undulator, free-electron-laser	412
	P.J.M. van der Slot, K.J. Boller Mesa+, Enschede, The Netherlands P.J.M. van der Slot CSU, Fort Collins, Colorado, USA
	Funding: This research is supported in part by Office of Naval Research Global, grant number N62909-10-1-7151 In order to understand and design free-electron lasers (FELs), simulation codes modeling the interaction of electrons with a co-propagating optical field in the magnetic field of an undulator are essential. However, propagation of the optical field outside the undulator is equally important for evaluation of the optical field at the location of the application or to model FEL oscillators. The optical propagation code OPC provides such capabilities and can interface with FEL gain codes like GENESIS 1.3, MEDUSA and MINERVA. Here we present recent additions and modifications to the code that (i) improves the speed of the code and (ii) extends the modeling capabilities. These include amongst other, inline diagnostics that results in considerable faster runtimes, the ability to convert from free-space modes to guided modes (currently only cylindrical waveguides), and the possibility to determine the spectrum at each transverse location. The latter opens the possibility to include dispersion in the optical propagation. Finally, work is underway to support HDF5 to remain compatible with the upcoming new release of GENESIS 1.3.

TUP022	The Implementation of 3D Undulator Fields in the Unaveraged FEL Simulation Code Puffin	undulator, FEL, focusing, simulation	416
	J. Henderson, L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom A.R. Maier CFEL, Hamburg, Germany A.R. Maier Uni HH, Hamburg, Germany
	Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20 The FEL simulation code Puffin is modified to include 3D magnetic undulator fields. Puffin, having previously used a 1D undulator field, is modified to accommodate general 3D magnetic fields. Both plane and curved pole undulators have been implemented. The electron motion for both agrees with analytic predictions.

TUP025	TW X-ray Free Electron Laser Optimisation by Transverse Pulse Shaping	FEL, radiation, undulator, simulation	425
	C. Emma, C. Pellegrini UCLA, Los Angeles, USA C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA
	We study the dependence of the peak power of a 1.5 Angstrom TW, tapered X-ray free-electron laser on the transverse electron density distribution. Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of 1.5 Angstrom using the fully 3-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30-70 % reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian.

TUP026	Transverse Coherence Properties of a TGU-based FEL	FEL, undulator, radiation, emittance	429
	P. Baxevanis, Z. Huang, R.D. Ruth SLAC, Menlo Park, California, USA C.B. Schroeder LBNL, Berkeley, California, USA
	The use of a transverse gradient undulator (TGU) is considered an attractive option for FELs driven by electron beams with a relatively large energy spread. In this scheme, a dispersion is introduced in the beam while the undulator poles are inclined so that the undulator field acquires a linear dependence upon the transverse position in the direction of dispersion. By suitably selecting the dispersion and the field gradient, the energy spread effect can be significantly mitigated, thus avoiding a drastic reduction in the FEL gain. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the output FEL radiation can become significant. To investigate this effect, we study the properties of the higher-order eigenmodes of a TGU-based, high-gain FEL, using both a simplified, analytically-solvable model and a variational technique. This formalism is then used to provide an estimate of the degree of transverse coherence for a representative soft X-ray, TGU FEL example.

TUP027	Initial Value Problem for an FEL Driven by an Asymmetric Electron Beam	FEL, radiation, undulator, simulation	433
	P. Baxevanis, R.D. Ruth SLAC, Menlo Park, California, USA
	FEL configurations in which the driving electron beam is not axially symmetric (round) are important in the study of novel concepts (such as TGU-based FELs) but also become relevant when one wishes to explore the degree to which the deviation from symmetry-inevitable in practical cases-affects the performance of more conventional FEL schemes. In this paper, we present a technique for solving the initial value problem of such an asymmetric FEL. Extending an earlier treatment of ours, we start from a self-consistent, fully 3D, evolution equation for the complex amplitude of the electric field of the FEL radiation, which is then solved by expanding the radiation amplitude in terms of a set of orthogonal transverse modes. The numerical results from such an analysis are in good agreement with simulation and provide a full description of the radiation in the linear regime. Moreover, when the electron beam sizes are constant, this approach can be used to verify the predictions of the standard eigenmode formalism.

TUP028	Mode Contents Analysis of a Tapered Free Electron Laser	FEL, undulator, laser, simulation	437
	S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S.D. Chen, C.-S. Hwang NCTU, Hsinchu, Taiwan C. Emma, C. Pellegrini UCLA, Los Angeles, USA K. Fang, S.-Y. Lee Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan S. Serkez DESY, Hamburg, Germany
	For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP029	iSASE Study	FEL, radiation, undulator, simulation	442
	K. Fang Indiana University, Bloomington, Indiana, USA S.D. Chen NCTU, Hsinchu, Taiwan S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA C. Emma, C. Pellegrini UCLA, Los Angeles, USA S. Reiche PSI, Villigen PSI, Switzerland
	Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

TUP030	Mode Component Evolution and Coherence Analysis in Terawatt Tapered FEL	FEL, undulator, radiation, laser	446
	K. Fang, S.D. Chen, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S.D. Chen NCTU, Hsinchu, Taiwan C. Emma, C. Pellegrini UCLA, Los Angeles, USA K. Fang Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan S. Serkez DESY, Hamburg, Germany
	A fast and robust algorithm is developed to decompose FEL radiation field transverse distribution into a set of orthonormal basis. Laguerre Gaussian and Hermite Gaussian can be used in the analysis. The information of mode components strength and Gaussian beam parameters allows users in downstream better utilize FEL. With this method, physics of mode components evolution from starting stage, to linear regime and post saturation are studied with detail. With these decomposed modes, correlation function can be computed with less complexity. Eigenmodes of the FEL system can be solved using this method.

TUP031	FEL Code Comparison for the Production of Harmonics via Harmonic Lasing	FEL, simulation, radiation, undulator	451
	G. Marcus, W.M. Fawley SLAC, Menlo Park, California, USA S. Reiche PSI, Villigen PSI, Switzerland E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Harmonic lasing offers an attractive option to significantly extend the photon energy range of FEL beamlines. Here, the fundamental FEL radiation is suppressed by various combinations of phase shifters, attenuators, and detuned undulators while the radiation at a desired harmonic is allowed to grow linearly. The support of numerical simulations is extensively used in evaluating the performance of this scheme. This paper compares the results of harmonic growth in the harmonic lasing scheme using three FEL codes: FAST, GENESIS, and GINGER.

TUP032	FEL Simulation and Performance Studies for LCLS-II	undulator, FEL, simulation, radiation	456
	G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang, J. Wu SLAC, Menlo Park, California, USA
	The design and performance of the LCLS-II free-electron laser beamlines are presented using start-to-end numerical particle simulations. The particular beamline geometries were chosen to cover a large photon energy tuning range with x-ray pulse length and bandwidth flexibility. Results for self-amplified spontaneous emission and self-seeded operational modes are described in detail for both hard and soft x-ray beamlines in the baseline design.

TUP033	Broadly Tunable Free-Electron Laser for Four-wave Mixing Experiments with Soft X-ray Pulses	undulator, FEL, laser, simulation	461
	G. Marcus SLAC, Menlo Park, California, USA G. Penn LBNL, Berkeley, California, USA A. Zholents ANL, Argonne, Illinois, USA
	This paper examines a FEL design for the production of three soft x-ray pulses from a single electron beam suitable for four-wave mixing experiments. Independent control of the wavelength, timing and angle of incidence of the three ultra-short, ultra-intense pulses with exquisite synchronization is critical. A process of selective amplification where a chirped electron beam and a tapered undulator are used to isolate the gain region to only a short fraction of the electron beam is explored in detail. Numerical particle simulations are used to demonstrate the essential features of this scheme in the context of the LCLS-II design study.

TUP036	Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls	radiation, experiment, simulation, free-electron-laser	470
	J.T. Donohue CENBG, Gradignan, France J. Gardelle, P. Modin CEA, LE BARP cedex, France
	In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".

TUP040	Flying RF Undulator	undulator, radiation, resonance, focusing	474
	A.V. Savilov, I.V. Bandurkin, S.V. Kuzikov, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	A new concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the -1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton’s photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse. This work is supported by the Russian Foundation for Basic Research (Projects 14-08-00803 and 14-02-00691).
	Poster TUP040 [0.189 MB]

TUP042	High Efficiency Lasing with a Strongly Tapered Undulator	undulator, laser, radiation, experiment	478
	J.P. Duris, P. Musumeci UCLA, Los Angeles, California, USA
	Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073 and University of California Office of the President award 09-LR-04-117055-MUSP. Typical electrical to optical energy conversion efficiencies for FELs are limited by the Pierce parameter to 10^-3 or smaller. Undulator tapering schemes have enabled extraction of as much as 1 or 2% of the electron energy. Recently, the UCLA BNL helical inverse free electron laser (IFEL) experiment at ATF demonstrated energy doubling and acceleration of 30% of an electron beam from 52 to 93 MeV with a modest 10¹¹ W power CO2 laser pulse. By reversing and retuning the undulator, the electrons may be violently decelerated, thereby transferring energy from the beam to the laser pulse. Simulations show that by sending a 1 kA, 70 MeV electron beam and 100 GW laser into a prebuncher and the reversed undulator, 41% of the electron beam energy should be converted to radiation, allowing the laser pulse power to grow to 127 GW.

TUP045	IFEL Driven Micro-Electro-Mechanical System Free Electron Laser	undulator, FEL, laser, radiation	481
	N.S. Sudar, J.P. Duris, P. Musumeci UCLA, Los Angeles, USA
	The Free Electron Laser has provided modern science with a tunable source of high frequency, high power, coherent radiation. To date, short wavelength FEL's have required large amounts of space in order to achieve the necessary beam energy to drive the FEL process and to reach saturation of the output radiation power. By utilizing new methods for beam acceleration as well as new undulator technology, we can decrease the space required to build these machines. In this paper, we investigate a scheme by which a tabletop XUV FEL might be realized. Utilizing the Rubicon Inverse Free Electron Laser (IFEL) at BNL together with micro-electro-mechanical system (MEMS) undulator technology being developed at UCLA, we propose a design for a compact XUV FEL.

TUP046	Terahertz FEL based on Photoinjector Beam in RF Undulator	undulator, focusing, FEL, radiation	485
	S.V. Kuzikov, I.V. Bandurkin, M.E. Plotkin, A.V. Savilov, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia A.V. Savilov NNGU, Nizhny Novgorod, Russia
	Photoinjectors, which can produce picosecond electron bunches of MeV-level, are attractive for THz generation. Fortunately, a long distance to reach scattering power saturation in FEL is not necessary, if bunch length is shorter than the produced THz half-wavelength. However, the energy of several MeVs does not allow providing long traveling of the flying bunch without longitudinal divergence. That is why, we suggest using specific RF undulator in a form of the normal wave in the helical waveguide at 3 cm wavelength. The mentioned wave has the -1st space harmonic with transverse fields and negative phase velocity (responsible for particle wiggling). This wave has also the 0th harmonic with longitudinal field and positive phase velocity equal to bunch velocity. Due to the synchronous 0th harmonic one can channel low-energy bunches (due to longitudinal focusing field) as far as several meters distance. One might also inject electron bunches in slightly accelerating field, in this case the output THz pulse obtain nearly linear frequency modulation. Such long THz pulses with the mentioned modulation of the frequency can be effectively compressed by pair of diffraction gratings.
	Poster TUP046 [2.914 MB]

TUP047	Chirped Pulse Superradiant Free-electron Laser	radiation, undulator, laser, FEL	489
	Y.-C. Huang, C.H. Chen NTHU, Hsinchu, Taiwan J. Wu, Z. Zhang SLAC, Menlo Park, California, USA
	Funding: This work is supported by Ministry of Science and Technology under Contract NSC 102-2112-M-007-002-MY3 When a short electron bunch traverses an undulator and radiates a wavelength significantly longer than the bunch length, the electrons quickly loses energy through so-called superradiance and generate a negatively chirped radiation frequency at the output. In this paper, we develop a theory to describe this chirped-pulse radiation and numerically demonstrate pulse compression by using a quadratic phase filter. As a design example at THz, a photoinjector/linac system generates a 15 MeV electron bunch containing 15-pC charge in a 60-fs duration. The electrons radiate a chirped pulse at 2.5 THz from a 1.5 m long undulator with a period of 5.6 cm and undulator parameter of 1.7. By using a grating pair, the output THz field can be compressed from 27 to 3 cycles. As another example at EUV, a future dielectric laser accelerator [1] is assumed to generate a 100 MeV electron bunch containing 75-fC charge in 1-nm long length. The electrons radiate a chirped EUV pulse at 13.5 nm from a 15.8 cm long dielectric laser undulator [2] with a period of 1.05 mm and undulator field of 3.3 T. By using a quadratic phase filter as a pulse compressor, the peak power of the EUV radiation is increased from 0.7 to 10 kW. Y.C. Huang and R.L. Byer, Appl. Phys. Lett. 69 (15), (1996) 2185-2177. *T. Plettner, R. L. Byer., Phys. Rev. ST Accel. Beams 11, (2008) 030704.

TUP054	Status of Electron Beam Slicing Project at NSLS-II, BNL	radiation, storage-ring, photon, linac	496
	A. He, F.J. Willeke, L.-H. Yu BNL, Upton, Long Island, New York, USA
	The Electron Beam Slicing (e-beam slicing) at NSLS-II, Brookhaven National Laboratory, supported by the Laboratory Directed Research and Development (LDRD) Program, is focused on the development of the new method to generate ultra-short x-ray pulses using focused short low energy (∼20 MeV) electron bunches to create short slices of electrons from the circulating electron bunches in a synchrotron radiation storage ring. The e-beam slicing activities are staged in 3 main phases. In Phases 0, the theory of e-beam slicing is developed, the low energy linac compressor is simulation designed, the radiation separation between the satellite and core is analyzed by simulation and the properties of the e-beam slicing system are discussed and compared with other ultra-short x- ray sources. Phase 0 has completed successfully, Phase 1 is under way. This paper presents an update on the status of Phase 0.

TUP057	Development of Compact THz-FEL System at Kyoto University	undulator, gun, FEL, simulation	501
	S. Suphakul, T. Kii, H. Ohgaki, Y. Tsugamura, H. Zen Kyoto University, Kyoto, Japan Q.K. Jia USTC/NSRL, Hefei, Anhui, People's Republic of China
	We are developing a compact accelerator based terahertz (THz) radiation source by free-electron laser (FEL) at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6 cell BNL type photocathode RF-gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles and an undulator. The system generates an ultra-short electron pulse in a few hundred femtoseconds shorter than radiation wavelength, resulting in super-radiant emission from the undulator. The target radiation wavelength is 100 to 300 μm. A tracking simulation and optimization are performed by using PARMELA and General Particle Tracer (GPT) code. The FEL radiations are analyzed by a 1 dimensional FEL theory. The design parameters, simulation results and status are reported and discussed in this paper.

TUP060	Potential Photochemical Applications of the Free Electron Laser Irradiation Technique in Living Organisms	FEL, experiment, radiation, laser	505
	F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan T. Kii, H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan T. Sakae Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan
	In 2001, the Laboratory for Electron Beam Research and Application (LEBRA) achieved the first lasing of 0.9–6.5 microns near-infrared free electron lasers (FELs), in which higher harmonics were generated by using nonlinear optical crystals. Following this breakthrough, we have paid considerable attention to LEBRA-FEL’s potential for investigating photochemical reactions in living organisms. We have established a micro-irradiation technique using an optical fiber connected to a fine tapered glass rod of <5 microns in diameter, enabling FEL irradiation of a single cell and even the inner organelles of live cells. We then verified that visible LEBRA-FEL light can control the germination of lettuce seeds, a well-known photochemical reaction, and determined that red light (660 nm FEL) promotes germination and far-red light (740 nm FEL) inhibits it. Here, we summarize the efficiency of various visible wavelengths of LEBRA-FEL light, ranging from 0.4–0.8 microns, for regulating photoreactions in lettuce seeds and we also summarize the efficiency of infrared wavelengths up to 20 microns, which can be generated by combined use of the LEBRA-FEL and the Kyoto University FEL. We thank the staff of Prof. T. Morii (Institute of Advanced Energy, Kyoto Univ.) for helpful assistance.

TUP064	Narrow Linewidth, Chirp-Control and Radiation Extraction Optimization in an Electrostatic Accelerator FEL Oscillator	FEL, laser, radiation, wiggler	509
	H. S. Marks, A. Gover, H. Kleinman, J. Wolowelsky University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel D. Borodin, M. Einat, M. Kanter, Y. Lasser, Yu. Lurie Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
	In recent years the electrostatic accelerator FEL based in Ariel has undergone many upgrades. By varying the accelerating potential the resonator allows lasing between 95-110 GHz. It is now possible to remotely control the output reflectivity of the resonator and thereby vary both the power built up in the resonator and that emitted. This has allowed fine control over the power for different user experiments. A voltage ramping device has been installed at the resonator/wiggler to correct drops in voltage which occur due to electrons striking the walls of the beam line. This has allowed stable pulses of just over 50 μs with a chirp rate of ~80 kHz/μs.

TUP066	Facility for Coherent THz and FIR Radiation	bunching, FEL, undulator, radiation	512
	A. Meseck HZB, Berlin, Germany V.G. Ziemann Uppsala University, Uppsala, Sweden
	Linac based THz sources are increasingly becoming the method of choice for a variety of research fields, justifying the increasing demand for high repetition rate THz FEL facilities world wide. In particular, pump and probe experiments with THz and IR radiation are of major interest for the user community. In this paper, we propose a facility which accommodates an SRF-linac driven cw THz-FEL in combination with an IR undulator which utilizes the microbunched beam. The layout permits almost perfect synchronization between pump and probe pulse as well as nearly independently tunable THz and IR radiation.
	Poster TUP066 [1.655 MB]

TUP070	Numerical Calculation of Diffraction Loss for Characterisation of a Partial Waveguide FEL Resonator	FEL, laser, simulation, radiation	521
	Q. Fu, B. Qin, P. Tan, K. Xiong, Y.Q. Xiong HUST, Wuhan, People's Republic of China
	Waveguide is widely used in long wavelength Free-Electron Lasers to reduce diffraction losses. In this paper the amplitude and phase transverse distribution of light emission produced in a partial-waveguide FEL resonator is calculated by Fresnel principle. To acquire high power out-coupled and optimize resonator structure of HUST THz-FEL, the characterisation of reflecting mirror is discussed to reduce diffraction loss.

TUP072	Present Status of Coherent Electron Cooling Proof-of-principle Experiment	cavity, ion, gun, laser	524
	I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb Tech-X, Boulder, Colorado, USA C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller Niowave, Inc., Lansing, Michigan, USA M.A. Kholopov, P. Vobly BINP SB RAS, Novosibirsk, Russia V. Litvinenko Stony Brook University, Stony Brook, USA P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP073	High Power Operation of the THz FEL at ISIR, Osaka University	FEL, operation, linac, gun	528
	K. Kawase, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, G. Isoyama, R. Kato, K. Kubo, K. Miyazaki, S. Suemine, A. Tokuchi, R. Tsutsumi, M. Yaguchi ISIR, Osaka, Japan
	The THz FEL at Osaka University is based on the L-band linac that provides a multi-bunch electron beam with an 8 us duration in the energy range from 12.5 to 20 MeV. Although the RF frequency of the linac is 1.3 GHz, the bunch intervals are expanded to 9.2 ns for the FEL using a sub-harmonic buncher system that operates at 10⁸ MHz, to enhance the bunch charge to 1 nC/bunch. The FEL covers the wavelength range from 30 to 150 um, and maximum energies of the macropulse and the micropulse are 3.7 mJ and 11 uJ, respectively, at ~70 um measured at an experimental station. To enhance the FEL power further, the electron beam current cannot be increased simply because the beam loading in the acceleration tube is too high. To solve this problem, we have developed a 27 MHz grid pulser for the thermionic electron gun that makes the bunch intervals 4 times longer and increases charge of the bunch 4 times higher whereas the beam loading is the same as that in the 108 MHz mode. In this new operation mode, where a single FEL pulse lases in the cavity, we have succeeded in obtaining the micropulse energy exceeding 100 uJ at a wavelength of 68 um.

TUP077	Characteristics of Transported Terahertz-wave Coherent Synchrotron Radiation at LEBRA	FEL, radiation, synchrotron-radiation, synchrotron	541
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan
	Funding: This work has been supported in part under the Visiting Researcher's Program of the Research Reactor Institute, Kyoto University, and ZE Research Program ZE25B-7, Kyoto University. Nihon University and National Institute of Advanced Industrial Science and Technology have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University since 2011. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator dedicated for an infrared free-electron laser (FEL), and confirmed it to be CSR []. Moreover, we have transported the CSR to an experimental room, which is next to the accelerator room across a shield wall, using an infrared FEL beamline. The transported CSR beam can be applied to two-dimensional imaging and spectroscopy experiments. In this presentation, characteristics of the CSR beam and applications for the CSR beam at LEBRA will be reported. N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104.

TUP079	A Swedish Compact Linac-based THz/X-ray Source at FREIA	cavity, radiation, gun, linac	545
	V.A. Goryashko Private Address, Uppsala, Sweden A. Opanasenko NSC/KIPT, Kharkov, Ukraine V. Zhaunerchyk University of Gothenburg, Gothenburg, Sweden
	THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP080	Towards an X-ray FEL at the MAX IV Laboratory	FEL, linac, gun, laser	549
	S. Werin, F. Curbis, M. Eriksson, C. Quitmann, S. Thorin MAX-lab, Lund, Sweden P. Johnsson Lund University, Lund, Sweden
	The design of the 3 GeV linac for the MAX IV facility was done to provide the ability to host a future FEL in the hard X-ray as well as in the soft X-ray range. The linear accelerator, with its two bunch compressors, is now under commissioning. Through the years increasing details for the actual FEL have been discussed and presented. In parallel a steering group for the science case for a Swedish FEL has worked and engaged a large number of Swedish user groups. These two paths are now converging into a joint project to develop the concept of an FEL at MAX IV. We will report on the paths to FEL performance based on the 3 GeV injector, FEL design considerations, the scientific preparation of the project, the linac commissioning and the strategy and priorities.

TUP081	Configuration and Status of the Israeli THz Free Electron Laser	FEL, wiggler, laser, RF-structure	553
	A. Friedman, N. Balal, V.L. Bratman, E. Dyunin, Yu. Lurie, E. Magori Ariel University, Ariel, Israel A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
	Funding: This project is funded in part by Israel Ministry of Defense. A THz FEL is being built in Ariel University. This project is a collaboration between Ariel University, and Tel Aviv University. Upon completion it is intended to become a user facility. The FEL is based on a compact photo cathode gun (60 cm) that will generate an electron beam at energies of 4.5 - 6.5 MeV. The pulses are planned to be of 300 pico Coulomb for a single pulse, and of up to 1.5 nano Coulomb for a train of pulses. The FEL is designed to emit radiation between 1 and 5 THz. It is planned to operate in the super radiance regime. The configuration of the entire system will be presented, as well as theoretical and numerical results for the anticipated output of the FEL, which is in excess of 150 KW instantaneous power. The bunching of the electron bean will be achieved by mixing two laser beams on the photo-cathode. The compression of the beam will be achieved be introducing an energy chierp to the beam and passing it through a helical chicane. We plan on compressing the single pulse to less than 150 femto seconds. The status of the project at the time of the conference will be presented.
	Poster TUP081 [3.276 MB]

TUP082	Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation	laser, radiation, undulator, experiment	556
	A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW. At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

TUP083	ALPHA – The THz Radiation Source based on AREAL	radiation, undulator, FEL, emittance	561
	T.L. Vardanyan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, B. Grigoryan, M. Ivanyan, V.G. Khachatryan, V.H. Petrosyan, V. Sahakyan, A. Sargsyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, G.S. Zanyan CANDLE SRI, Yerevan, Armenia
	Advanced Research Electron Accelerator Laboratory (AREAL) based on photo cathode RF gun is under construction at the CANDLE. The basic aim of this new facility is to generate sub-picosecond duration electron bunches with an extremely small beam emittance and energies up to 50 MeV. One of the promising directions of the facility development is the creation of ALPHA (Amplified Light Pulse for High-end Applications) experimental stations with coherent radiation source in THz region based on the concept of both conventional undulator and novel radiation sources. The status of the AREAL facility, the main features and outlooks for the ALPHA station are presented in this work.

TUP085	FERMI Status Report	FEL, experiment, laser, operation	564
	M. Svandrlik, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, L. Fröhlich, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI, the seeded FEL located at the Elettra laboratory in Trieste, Italy, is now in regular operation for users with its first FEL line, FEL-1, which covers the wavelength range between 100 and 20 nm. We will give an overview of the typical operating modes of the facility for users and we will report on the status of beamlines and experimental stations. Three beamlines are now opened for users, three more are in construction. Meanwhile, the second FEL line of FERMI, FEL-2, a HGHG double stage cascade covering the wavelength range 20 to 4 nm is still under commissioning; we will report on the latest results in particular at the shortest wavelength, 4 nm in the fundamental.

TUP086	Experiment Preparation Towards a Demonstration of Laser Plasma Based Free Electron Laser Amplification	laser, undulator, FEL, free-electron-laser	569
	M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Cassinari, L. Chapuis, M.E. El Ajjouri, C. Herbeaux, N. Hubert, M. Labat, A. Lestrade, A. Loulergue, J. Lüning, O. Marcouillé, J.L. Marlats, F. Marteau, C. Miron, P. Morin, F. Polack, K. Tavakoli, M. Valléau, D. Zerbib SOLEIL, Gif-sur-Yvette, France I.A. Andriyash, G. Lambert, V. Malka, C. Thaury LOA, Palaiseau, France S. Bielawski, C. Evain, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France X. Davoine CEA/DAM/DIF, Arpajon, France
	One direction towards compact Free Electron Laser is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence. Applying seeding techniques also enables to reduce the required undulator length. Rapidly developing Laser Wakefield Accelerators (LWFA) are already able to generate synchrotron radiation. With the presently achieved electron divergence and energy spread an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract in the more general context of LUNEX5. Electron beam transport follows different steps with strong focusing thanks to variable strength permanent magnet quadrupoles, demixing chicane with conventional dipoles, and a second set of quadrupoles for further focusing in the undulator. Progress on the equipment preparation and expected performance are described.

TUP087	The Status of LUNEX5 Project	FEL, laser, undulator, operation	574
	M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Cassinari, L. Chapuis, J. Daillant, M. Diop, M.E. El Ajjouri, C. Herbeaux, N. Hubert, M. Labat, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, C. Miron, P. Morin, A. Nadji, F. Polack, F. Ribeiro, J.P. Ricaud, P. Roy, K. Tavakoli, M. Valléau, D. Zerbib SOLEIL, Gif-sur-Yvette, France S. Bielawski PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France B. Carré, D. Garzella CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France X. Davoine CEA/DAM/DIF, Arpajon, France N. Delerue LAL, Orsay, France G. Devanz, A. Mosnier CEA/DSM/IRFU, France A. Dubois, J. Lüning CCPMR, Paris, France C. Evain, E. Roussel, C. Szwaj PhLAM/CERLA, Villeneuve d'Ascq, France G. Lambert, R. Lehé, V. Malka, A. Rousse, C. Thaury LOA, Palaiseau, France C. Madec CEA/IRFU, Gif-sur-Yvette, France
	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, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling seeding with High order Harmonic in Gas and echo configurations and pilot user applications. Concerning the superconducting linac, the electron beam dynamics has been modified from a scheme using a third harmonic linearizer and a compression chicane to dog-leg coupled to sextupoles. Besides, the choice of the gun is under revision for fulfilling to 10 kHz repetition rate. Following transport theoretical studies of longitudinal and transverse manipulation of a LWFA electron beam enabling to provide theoretical amplification, a test experiment is under preparation in collaboration with the Laboratoire d’Optique Appliquée towards an experimental demonstration.

TUP088	Free Electron Lasers in 2014	FEL, undulator, laser, free-electron-laser	580
	J. Blau, K. R. Cohn, W.B. Colson, W.W. Tomlinson NPS, Monterey, California, USA
	Funding: This work has been supported by the Office of Naval Research and the High Energy Laser Joint Technology Office. Thirty-eight 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.

TUP089	The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) Project	undulator, FEL, radiation, linac	585
	A.A. Aksoy, Ö. Karslı, C. Kaya, O. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey P. Arıkan Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey S. Özkorucuklu Istanbul University, Istanbul, Turkey
	Funding: Work is supported by Ministry of Development of Turkey with Grand No: DPT2006K-120470 The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) which is proposed as a first facility of Turkish Accelerator Center (TAC) Project will operate two Infra-Red Free Electron Lasers (IR-FEL) covering the range of 3-250 microns. The facility will consist of an injector fed by a thermionic triode gun with two-stage RF bunch compression, two superconducting accelerating modules operating at continuous wave (CW) mode and two independent optical resonator systems with different undulator period lengths. The electron beam will also be used to generate Bremsstrahlung radiation. The facility aims to be first user laboratory in the region of Turkey in which both electromagnetic radiation and particles will be used. In this paper, we discuss design goals of the project and present status and road map of the project.

TUP093	A Beam Test of Corrugated Structure for Passive Linearizer	simulation, quadrupole, linac, controls	593
	H.-S. Kang, J.H. Hong PAL, Pohang, Kyungbuk, Republic of Korea
	A dechirper which is a vacuum chamber of two corrugated, metallic plates with adjustable gap was successfully tested at Pohang, in August 2013. Another beam test was carried out to test the same structure to see if the corrugated plates may work as a linearizer. The test result will be presented together with the simulation result.

TUP095	Design of a Compact Light Source Accelerator Facility at IUAC, Delhi	gun, radiation, undulator, laser	596
	S. Ghosh, R.K. Bhandari, G.K. Chaudhari, D. Kanjilal, J. Karmakar, N. Kumar, A. Pandey, P. Patra, A. Rai, B.K. Sahu IUAC, New Delhi, India A.S. Aryshev, J. Urakawa KEK, Ibaraki, Japan A. Deshpande, T.S. Dixit SAMEER, Mumbai, India V. Naik, A. Roy VECC, Kolkata, India
	Funding: * The project is supported jointly by Board of Research in Nuclear Sciences and Inter University Accelerator Center The demand for a light source with high brightness and short pulse length from the researchers in the field of physical, chemical, biological and medical sciences is growing in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source at Inter University Accelerator Centre (IUAC) has been taken up. In the first phase of the project, prebunched [1] electron beam of ~ 8 MeV will be produced by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the second phase, the energy of the electron beam will be increased up to 50 MeV by two sets of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper the detailed design of the LSI accelerator complex as well as construction timetable will be presented. The physical principles of THz generation and major accelerator subsystems will be discussed. [1] S. Liu & J.Urakawa, Proc. of FEL 2011, page-92

TUP097	Fast, Multi-band Photon Detectors based on Quantum Well Devices for Beam-monitoring in New Generation Light Sources	detector, laser, photon, monitoring	600
	T. Ganbold University of Trieste, School of Nanotechnology, Trieste, Italy M. Antonelli, G. Cautero, R. Cucini, D.M. Eichert, W.H. Jark, R.H. Menk Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy G. Biasiol IOM-CNR, Trieste, Italy
	In order to monitor the photon-beam position for both diagnostics and calibration purposes, we have investigated the possibility to use InGaAs/InAlAs Quantum Well (QW) devices as position-sensitive photon detectors for Free-Electron Laser (FEL) or Synchrotron Radiation (SR). Owing to their direct, low-energy band gap and high electron mobility, such QW devices may be used also at Room Temperature (RT) as fast multi-band sensors for photons ranging from visible light to hard X-rays. Moreover, internal charge-amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. Segmented QW sensors have been preliminary tested with 100-fs-wide UV laser pulses and X-ray SR. The reported results indicate that these devices respond with 100-ps rise-times to ultra-fast UV laser pulses. Besides, X-ray tests have shown that these detectors are sensitive to beam position and exhibit a good efficiency in the collection of photo-generated carriers.

TUC01	Hard X-ray Self-Seeding Setup and Results at SACLA	undulator, FEL, radiation, photon	603
	T. Inagaki, N. Adumi, T. Hara, T. Ishikawa, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan S. Goto, Y. Inubushi, T.K. Kameshima, T. Ohata, K. Tono JASRI/SPring-8, Hyogo, Japan T. Hasegawa, S. Tanaka SES, Hyogo-pref., Japan H. Kimura, A. Miura, H. Ohashi, H. Yamazaki Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan
	In order to improve the spectral and temporal properties of XFEL, the self-seeding option based on the transmission crystal optics has been implemented in SACLA since 2012. The self-seeding setup composed of four dipole magnets that can generate up to 50 fs temporal delay and a diamond single crystal with the thickness of 180 micro-m has been installed at the position of the 9th undulator segment, which has been moved downstream. In 2013, the installation of all the components has been completed in August and the commissioning has been started in October. After a number of tuning processes such as the beam collimation and undulator K-value optimization, significant spectral narrowing has been confirmed at 10 keV with the C(400) Bragg reflection. The spectral bandwidth of seeded FEL is about 3 eV, which is nearly one order narrower than that of SASE measured without the diamond crystal. The peak spectral intensity of seeded FEL is about 5 times higher than that of SASE. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs. This talk gives the overview of the plan, achieved results and ongoing R&D.
	Slides TUC01 [20.337 MB]

TUC03	Generation of Optical Orbital Angular Momentum Using a Seeded Free Electron Laser	laser, FEL, radiation, free-electron-laser	609
	P. Rebernik Ribič, G. De Ninno, D. Gauthier Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Paper

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MOA01

Remembering Samuel Krinsky

FEL, laser, free-electron-laser, experiment

1

L.-H. Yu
BNL, Upton, Long Island, New York, USA

The presentation recalls the person, life, and achievements of Samuel Krinsky, who passed away this year.

Slides MOA01 [5.784 MB]

MOA03

First Lasing at FLASH2

undulator, operation, photon, laser

7

S. Schreiber, B. Faatz
DESY, Hamburg, Germany

FLASH, the free-electron laser user facility at DESY (Hamburg, Germany), has been upgraded with a second undulator beamline FLASH2. The installation of the FLASH2 electron beamline, including twelve variable gap undulators, was finalized early 2014, and beam commissioning of the new beamline started in March 2014. We announce first lasing at FLASH2 achieved at a wavelength of 40 nm on August 20, 2014.

Slides MOA03 [3.896 MB]

MOB01

Pulse Control in a Free Electron Laser Amplifier

FEL, radiation, laser, undulator

9

L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy

Funding: Work supported by MIUR (DM1834 RIC.4-12-2002 and Grants No. FIRB- RBAP045JF2 and No. FIRB-RBAP06AWK3), and by the EU Commission in the Sixth Framework Program, Contract No. 011935- EUROFEL.
A significant progress has been made in controlling the properties of the radiation emitted by a FEL amplifier. Experiments have demonstrated the possibility both to increase the temporal coherence and to reduce the amplifier length to reach saturation, by seeding it with an external source. This may be a solid state, short pulse, laser (Ti:Sa,OPA..), doubled or tripled in a crystal, or a high order harmonic pulse generated in gas. The coherence improvement and the increased compactness of the source are only the first beneficial offspring of this marriage between the optical laser world and that of FELs. Non-linear effects in the seeded FEL dynamics may be exploited to shorten the pulse length beyond that allowed by the FEL natural gain bandwidth. Multiple seed pulses can be used to generate pulses whose temporal distance and properties are also controlled. Similarly, the FEL gain can be adapted to match the seed properties by tailoring the electrons phase space to generate ultra-short output pulses at unparalleled intensities. I had the honor (and luck) to participate in many relevant experiments at the SPARC and FERMI FELs and I will give my personal overview.

Slides MOB01 [29.932 MB]

MOB02

Small-scale Accelerator-based Radiation Sources and Their Applications

FEL, experiment, target, free-electron-laser

14

Y.U. Jeong
KAERI, Daejon, Republic of Korea

Small-scale accelerator-based radiation sources can be used more widely for developing advanced technologies and exploring new science with high convenience and low cost. Sometimes they are competitive comparing with giant facilities like X-ray free-electron lasers (X-FELs). We have developed a table-top terahertz (THz) FEL for substituting X-ray or millimeter-wave-based security imaging technologies (body scanners) and a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. I will present on the status of the development of the small-scale radiation sources and plans for the pump-probe experiments. Additionally recent research results on biological study with the operating KAERI (Korea Atomic Energy Research Institute) THz FEL will be given.

Slides MOB02 [32.237 MB]

MOB03

Phase Space Manipulations in Modern Accelerators

laser, FEL, cavity, radiation

16

D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

Funding: This work was supported by the National Natural Science Foundation of China under Grants No. 11327902.
Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities.

Slides MOB03 [5.078 MB]

MOP001

Particle Tracking Simulations for EXFEL Complex shape Collimators

radiation, simulation, lattice, photon

22

V.G. Khachatryan, V.H. Petrosyan, T.L. Vardanyan
CANDLE SRI, Yerevan, Armenia

The study sets the objective to investigate through numerical simulation the produced secondary radiation properties when the electron beam particles hit collimator walls. Using particle tracking simulation code FLUKA, the European XFEL electron beam as well as beam halo interaction with the collimator were simulated. The complex geometrical shape and material composition of the collimator have been taken into account. Absorbed dose spatial distribution in the material of the collimators and particle fluencies from the downstream surface of the collimator were simulated for the total secondary radiation and its main components.

MOP007

High Accuracy Shimming Technique for the Phase Shifters of the European XFEL

undulator, operation, simulation, permanent-magnet

29

Y. Li
DESY, Hamburg, Germany
J. Pflüger
XFEL. EU, Hamburg, Germany

For the European XFEL 91 phase shifters are needed, which have to fulfil stringent field integral specifications: There should be no observable beam deflection when the strength, i.e. the magnetic gap is changed In order to facilitate the mass production of 91 phase shifters within the tough XFEL schedule a shimming technique was developed. It is based on measured shim signatures and is straight forward and fast to apply. The method is described and results are presented demonstrating that all requirements can be fulfilled.

MOP012

Implementation Phase of the European XFEL Photon Diagnostics

photon, diagnostics, undulator, FEL

41

J. Grünert, J. Buck, F. Dietrich, W. Freund, A. Koch, M. Planas
XFEL. EU, Hamburg, Germany

The European XFEL facility with 3 undulators and initially 6 experimental end-stations requires an extensive set of photon beam diagnostics for commissioning and user operation, capable of handling the extreme brilliance and its inherent damage potential, and the high intra bunch train repetition rate of 4.5MHz, potentially causing additional damage by high heat loads and making shot-to-shot diagnostics very demanding [1]. After extensive design [2-4] and prototype studies, in 2014 the installation of the photon beam devices starts with the equipment in the first photon tunnel XTD2 which is where the SASE1 hard X-ray undulator is located. This contribution reports on the device construction progress by focusing on the XTD2 tunnel devices and their implementation into the tunnel environment. [1] J.Grünert, Framework for X-Ray Photon Diagnostics at the European XFEL, TR-2012-003, 04/2012 [2] J.Buck, Online Photoemission Time-of-Flight Spectrometer for X-ray Photon Diagnostics, TR-2012-002, 06/2012 [3] C.Ozkan, Conceptual design report for Imaging Stations at the European XFEL, TR-2012-004, 02/2012 [4] W.Freund, The European XFEL Undulator Commissioning Spectrometer, XFEL. EU 05/2011

MOP014

X-ray Photon Temporal Diagnostics for the European XFEL

photon, diagnostics, brilliance, laser

45

J. Liu, J. Buck, F. Dietrich, W. Freund, J. Grünert, M. Meyer
XFEL. EU, Hamburg, Germany

European XFEL (XFEL. EU) that will commissioning in 2016 shows great features on its extremely high number of light bullets (27000 p/s) and extremely high average brilliance. The FEL pulses in XFEL. EU are produced in a 10 Hz bunch trains that contains 2700 sub-pulses within the 600 μs time intervals, corresponding to a 220 ns sub-pulse separation and 4.5 MHz repetition rate. Characterizing the temporal properties of the high repetition rate FEL pulses that implicitly different from shot to shot is important for “pump and probe” experiments and data interpretation. Here we report the concept and recent progress about temporal diagnostic for XFEL. EU. THz streaking technique and spectral encoding will be implemented considering the high repetition rate and high brilliance of XFEL. EU. Laser based THz generation, optimization and numerical simulation for streaking FEL electrons with different photon energies will be presented. High repetition rate diagnostic requirements and solutions will also be discussed.

MOP015

A Power Switching Ionization Profile Monitor (3D-IPM)

laser, ion, detector, vacuum

47

H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu
DESY Zeuthen, Zeuthen, Germany

FLASH at DESY in Hamburg is a linear accelerator to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position and profile changes of the beam. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined evaluation of the horizontal and vertical position as well as the profile. A compact monitor, consisting of two micro-channel plates (MCP) is assembled on a conducting cage along with toggled electric fields in a rectangular vacuum chamber. The particles created by the photon beam, drift in the homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for assessment. This indirect detection scheme operates over a wide dynamic range and allows the live detection of the clear position and the shape of the beam. The final design is presented.

Poster MOP015 [1.314 MB]

MOP017

Measurement of the Output Power in Millimeter Wave Free Electron Laser using the Electro Optic Sampling Method

laser, FEL, radiation, detector

50

A. Klein
Israeli Free Electron Laser, Ariel, Israel
A. Abramovich
Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
D. Borodin, A. Friedman
Ariel University, Ariel, Israel
H. S. Marks
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel

Funding: this work funded in part by Israel Minstry of Defence
In this experimental work an electro optic (EO) sampling method was demonstrated as a method to measure the output power of an Electrostatic Accelerator Free Electron Laser (EA-FEL). This 1.4 MeV EA-FEL was designed to operate at the millimeter wavelengths and it utilizes a corrugated waveguide and two Talbot effect quasi-optical reflectors with internal losses of ~30%. Millimeter wave radiation pulses of 10 μs at a frequency of about 100 GHz with peak power values of 1-2 kW were measured using conventional methods with an RF diode. Here we show the employment of an electro-optic sampling method using a ZnTe nonlinear crystal. A special quasi optical design directs the EA-FEL power towards the ZnTe nonlinear crystal, placed in the middle of a cross polarized configuration, coaxially with a polarized HeNe laser beam. The differences in the ZnTe optical axis due to the EA-FEL power affects the power levels of the HeNe laser transmission. This was measured using a polarizer and a balanced amplifier detector. We succeeded in obtaining a signal which corresponds to the theoretical calculation.

MOP018

Conceptual Study of a Self-seeding Scheme at FLASH2

undulator, FEL, simulation, photon

53

T. Plath, L.L. Lazzarino
Uni HH, Hamburg, Germany
K.E. Hacker
DELTA, Dortmund, Germany

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K1GU4 and 05K10PE1 and the German Research Foundation program graduate school 1355.
We present a conceptual study of a self-seeding installation at the new FEL beamline, FLASH2, at the free-electron laser at DESY, Hamburg. For self-seeding, light from a first set of undulators is filtered by a monochromator and thus acts as a seed for the gain process in the main undulator. This scheme has been tested at LCLS at SLAC with a diamond monochromator for hard X-rays and with a grating monochromator for soft X-rays covering energies between 700 and 1000 eV. For such a design to offer benefits at FLASH2, it must be modified to work with X-rays with wavelength of about 5 nm (248 eV) where the damage threshold of the monochromator in the setup and the divergence at longer wavelengths become an issue. An analysis of the potential performance and limitations of this setup is performed using GENESIS 1.3 and a method developed for the soft X-ray self-seeding experiment at the European XFEL. With a total of 9 undulators in the first stage and 8 undulators after the monochromator, a pulse energy contrast ratio of 4.5 was simulated with an initial peak current of 2.5 kA.

MOP022

Pulse by Pulse Electron Beam Distribution for Multi-beamline Operation at SACLA

operation, kicker, septum, linac

71

T. Hara, T. Inagaki, C. Kondo, Y. Otake, H. Takebe, H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
K. Fukami
JASRI/SPring-8, Hyogo-ken, Japan

In order to meet the increasing demand for XFEL user operation, the second undulator beamline (BL2) will be installed during the 2014 summer shutdown at SACLA. Following the installation of BL2, a pulse by pulse electron beam distribution system composed of a kicker and a DC twin-septum magnet, which are currently under development, is planned be installed in January 2015. To distribute the electron beam on a bunch-to-bunch basis, the electron beam is deflected into 0 and ±10 mrad directions at 60 Hz by the kicker, and then the DC twin-septum magnet augments the separation angle to ±50 mrad. The kicker magnet is driven by a 60 Hz trapezoidal waveform and stability less than 30 ppm (peak-peak) has been achieved. This pulse by pulse distribution system will be also used for the beam injection to the upgraded low emittance ring of SPring-8 (SPring-8-II) in future. Since the SPring-8-II storage ring has a small dynamic aperture, low emittance is required for the injection beam. Also the beam injection in parallel with the XFEL operation enables to save the running cost of the injector during top-up operation.

MOP028

Field Integral Measurement System and Optical Alignment System for HUST THz-FEL

undulator, FEL, alignment, cavity

80

B. Qin, Q.S. Chen, M. Fan, Q. Fu, T. Hu, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang
HUST, Wuhan, People's Republic of China
X. Liu, Z. Ouyang, Y.B. Wang
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
Y.J. Pei
USTC/NSRL, Hefei, Anhui, People's Republic of China

A Free Electron Laser oscillator with radiation wavelength 50–100 μm is under construction in Huazhong University of Science and Technology (HUST). The linear polarization undulator with K=1.0-1.25 has been designed and manufactured by Kyma s.r.l., by using a pure permanent magnet scheme. Acceptance test bas been performed in Kyma factory with well controlled phase error and field integrals for all gaps. This paper introduces the development of an online field integrals measurement system for the undulator, using the stretched wire method. The design and considerations of the optical alignment system is described as well.

MOP036

Estimating Effect of Undulator Field Errors using the Radiation Hodograph Method

undulator, radiation, synchrotron-radiation, free-electron-laser

93

N.A. Sokolov
Budker INP & NSU, Novosibirsk, Russia
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

Spatially-periodic magnetic structures are widely used for generation of high-brilliance radiation in storage rings, sources of synchrotron radiation and free electron lasers. In 1947, V.L. Ginzburg suggested the first undulator scheme. An alternating magnetic field created by a planar undulator makes electrons oscillate in the transverse direction, with interference of radiation emitted from separate parts of the trajectory. The spectrum of the forward emitted radiation is enchanced due to constructive interference. The ondulator is made of the magnetized bars that are not perfect and their magnetization differs. Therefore, the electron trajectory is not purely sinusoidal and, as a result, the spectral intensity fades. The task was to find out if the precision of magnet manufacturing is sufficient. This paper presents modelling of electron motion in the measured magnetic field of the new (third) free electron laser at the Siberian Synchrotron Radiation Centre. We have managed to estimate the effect of the field errors through comparison of the resulting emitted field amplitude with the amplitude from ideal magnet bars using the hodograph method.

MOP037

Modeling and Design of the Variable Period and Pole Number Undulator for the Second Stage of the Novosibirsk FEL

undulator, FEL, simulation, permanent-magnet

96

I. Davidyuk
NSU, Novosibirsk, Russia
O.A. Shevchenko, V.G. Tcheskidov, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia
N. Vinokurov
KAERI, Daejon, Republic of Korea

The concept of the permanent magnet variable period undulator (VPU) has been proposed just several years ago and there are few examples of its implementation yet. The VPUs have several advantages compared to conventional undulators. One of them is wider radiation wavelength tunability range and another one is an option to increase the number of poles for shorter periods. Both these advantages will be realized in VPU which is being developed now at Budker INP. In this paper we present the 2-D and 3-D magnetic field simulation results and discuss the design features of this VPU.

MOP038

Characterization of the Undulator Magnetic Field Quality by the Angle Averaged Radiation Spectrum

undulator, radiation, photon

100

O.A. Shevchenko, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia
N. Vinokurov
KAERI, Daejon, Republic of Korea

The real undulator magnetic field always contains errors which influence undulator performance. The effect of these errors is usually characterized by broadening of the spontaneous emission spectrum at zero angle and corresponding reduction of the spectral intensity. This approach works very well for the phase errors while it does not take into account transversal trajectory displacements. The integrated over the angles radiation spectrum contains more complete information about the undulator field quality but its calculation requires more effort. Therefore the spectral density of emitted radiation (the total number of emitted photons with given energy) can be considered as a figure of merit for an undulator. In this paper we derive analytical formula for this spectrum suitable for doing efficient numerical calculations and demonstrate its application to the case of some typical undulator field errors.

MOP039

High Stability Resonant Kicker Development for the SwissFEL Switch Yard

kicker, operation, dipole, linac

103

M. Paraliev, H.-H. Braun, S. Dordevic, C.H. Gough
PSI, Villigen PSI, Switzerland

The SwissFEL is a linac-based X-ray free electron laser facility under construction at the Paul Scherrer Institute. The facility will provide femtosecond, high brightness X-ray pulses for fundamental and applied science research. To increase facility efficiency, a double bunch operation is planned to serve simultaneously two experimental stations at the full linac repetition rate. The main linac will accelerate two electron bunches spaced 28 ns apart and a fast and stable deflecting system will be used to separate the two bunches into two different undulator lines. The deflecting system uses a novel concept based on resonant kicker magnets. A prototype kicker magnet and its control system were designed and built. Since stability is crucial, the stability performance of the prototype was studied. The peak to peak amplitude stability of ±11 ppm (3.5 ppm rms) was achieved, which is well within the FEL tolerance of ±80 ppm. The layout of the deflecting system and the key design parameters are also presented.

MOP040

General Strategy for the Commissioning of the ARAMIS Undulators with a 3 GeV Electron Beam

undulator, alignment, quadrupole, photon

107

M. Calvi, M. Aiba, M. Brügger, S. Danner, R. Ganter, R. Ischebeck, L. Patthey, T. Schietinger, T. Schmidt
PSI, Villigen PSI, Switzerland

The commissioning of the first SwissFEL undulator line (Aramis) is planned for the beginning of 2017. Each undulator is equipped with a 5-axis camshaft system to remotely adjust its position in the micrometer range and a gap drive system to set K-values between 0.1 and 1.8. In the following paper the beam-based alignment of the undulator with respect to the golden orbit, the definition of look-up tables for the local correction strategy (minimization of undulator field errors), the fine-tuning of the K-values as well as the setting of the phase shifters are addressed. When applicable both electron beam and light based methods are presented and compared.

MOP041

Summary of the U15 Prototype Magnetic Performance

undulator, vacuum, quadrupole, photon

111

M. Calvi, M. Aiba, M. Brügger, S. Danner, R. Ganter, C. Ozkan, T. Schmidt
PSI, Villigen PSI, Switzerland

The first undulator prototype (U15) was assembled and magnetically tested. The instrumentation and the algorithms developed for the undulator optimization are presented and a comparison among different approaches is reviewed. The magnetic measurement results before and after the installation of the vacuum components are discussed. The summary of the undulator test with 100 MeV electron beam is presented and the impact of the radiation on the magnetics is addressed.

MOP045

Phase Shifter Design for iSASE

power-supply, undulator, FEL, simulation

123

S.D. Chen, K. Fang, H.-D. Nuhn, C. Pellegrini, J. Wu, L. Zhu
SLAC, Menlo Park, California, USA
S.D. Chen, C.-S. Hwang
NCTU, Hsinchu, Taiwan
K. Fang
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan

A phase shifter to generate an additional phase advance of the spontaneous light versus the electron beam was de- signed for the iSASE scheme. The iSASE mechanism is for reducing the bandwidth further from SASE FEL process. A large phase advance about 1600*2Pi as the FEL operating at wavelength 0.8 nm was needed according to the simulation of iSASE process. Since the iSASE is thought to implement into LCLS II project, the space limitation causing by LCLS II should be considered when designing the phase shifter. An optimized three-pole electric phase shifter with 7.3 mm gap has the center field of 1.8 T . The vanadium steel was considered as pole material and the magnet physical length is 260 mm, meanwhile the water-cooling type copper coil was adopted. The temperature increment, force analysis, low field operation mode concept, and preliminary tolerance study were discussed.

MOP046

Undulator Radiation Damage Experience at LCLS

undulator, radiation, operation, experiment

127

H.-D. Nuhn, R.C. Field, Yu.I. Levashov, X.S. Mao, M. Santana-Leitner, J.J. Welch, Z.R. Wolf
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checked for magnetic (50 ppm, rms) and mechanic (about 0.25 μm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.

MOP047

A 200 μm-period Laser-driven Undulator

undulator, laser, plasma, alignment

131

F. Toufexis, T. Tang, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515 and the DARPA AXiS program.
To reduce the linac energy required for a given synchrotron radiation wavelength, and hence the size of the device, a smaller undulator period with sufficient field strength is needed. In this work, a microfabricated, laser-driven undulator with 200um undulator period is proposed. A TE wave that co-propagates with the electron beam is excited between two polysilicon thin films, having a gap of 16.5um. The mode that is excited is a deflecting mode and causes the electron beam to wiggle. The device is fabricated on a silicon wafer, using conventional silicon micromachining techniques. A single polysilicon thin film is supported on a silicon chip, which has a slit from the back to allow delivery of the laser beam. Two such chips are bonded together to form a 16.5um gap, within which the electron beam passes through. The final device has dimensions 1cm x 1cm x 1.1mm and has approximately 35 undulator periods. In this paper, the model, design, fabrication, and cold measurements of the device are reported.

MOP049

Oxygen Scintillation in the LCLS

detector, controls, laser, instrumentation

137

J.L. Turner, R.C. Field
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Oxygen is tested as a replacement for Nitrogen in the Gas Detector system in the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center. The attenuation and energy monitors for LCLS use Nitrogen, but for experiments at the Nitrogen K 1S energy of about 410eV this functionality is gone due to energy fluctuations above and below the K-edge. Oxygen was tested as a scintillating gas at 400eV and 8.3keV.

MOP053

SASE FEL Performance at the SwissFEL Injector Test Facility

FEL, undulator, simulation, gun

144

S. Reiche
PSI, Villigen PSI, Switzerland

A 4 m long prototype of the SwissFEL undulator module with an undulator period length of 15 mm was installed at the SwissFEL Injector Test Facility and tested with a 200 MeV electron beam in the beginning of 2014. We observed FEL lasing in SASE mode in the wavelength range from 70 to 800 nm, tuning the wavelength by energy and gap. The measurements of the FEL performance are reported.
on behalf of the SwissFEL Team

MOP054

Harmonic Lasing Options for LCLS-II

undulator, photon, radiation, FEL

148

G. Marcus, Y. Ding, Z. Huang, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
G. Penn
LBNL, Berkeley, California, USA

Harmonic lasing can be a cheap and relatively efficient way to extend the photon energy range of a particular FEL beamline. Furthermore, in comparison to nonlinear harmonics, harmonic lasing can provide a beam that is more intense, stable, and narrow-band. This paper explores the application of the harmonic lasing concept at LCLS-II using various combinations of phase shifters and attenuators. In addition, a scheme by which individual undulator modules are tuned to amplify either the third or fifth harmonic in different configurations is presented in detail.

MOP055

Start-to-End Simulations for IR/THz Undulator Radiation at PITZ

radiation, undulator, FEL, simulation

153

P. Boonpornprasert, M. Khojoyan, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany
B. Marchetti, E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany
S. Rimjaem
Chiang Mai University, Chiang Mai, Thailand

High brightness electron sources for modern linac-based Free-Electron Lasers (FELs) have been characterized and optimized at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Since the time structure of the electron bunches at PITZ is identical to those at the European XFEL, the PITZ accelerator is being considered as a proper machine for the development of an IR/THz source prototype for pump and probe experiments planned at the European XFEL. Tunable IR/THz radiation sources using synchrotron radiation from a dipole magnet, transition radiation, high gain FELs and coherent radiation of tailored or premodulated beams are currently under consideration. This work describes start-to-end simulations for generating the FEL radiation using an APPLE-II undulator with electron beams produced by the PITZ accelerator. Analysis of the physical parameter space has been performed with tools of the FAST program code package. Electron Beam dynamics simulations were performed by using the ASTRA code, while the GENESIS 1.3 code was used to study the SASE process. The results of these studies are presented and discussed in this paper.

MOP056

SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime

photon, undulator, radiation, FEL

159

I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany
G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany

The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime.

MOP057

Proposal to Generate 10 TW Level Femtosecond X-ray Pulses from a Baseline Undulator in Conventional SASE Regime at the European XFEL

undulator, laser, free-electron-laser, FEL

164

E. Saldin, V. Kocharyan, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
G. Geloni
XFEL. EU, Hamburg, Germany

Output characteristics of the European XFEL have been previously studied assuming an operation point at 5 kA peak current. Here we explore the possibility to go well beyond such nominal peak current level. We consider a bunch with 0.25 nC charge, compressed up to a peak current of 45 kA. An advantage of operating at such high peak current is the increase of the x-ray output peak power without any modification to the baseline design. Based on start-to-end simulations, we demonstrate that such high peak current, combined with undulator tapering, allows one to achieve up to a 100-fold increase in a peak power in the conventional SASE regime, compared to the nominal mode of operation. In particular, we find that 10 TW-power level, femtosecond x-ray pulses can be generated in the photon energy range between 3 keV and 5 keV, which is optimal for single biomolecule imaging. Our simulations are based on the exploitation of all the 21 cells foreseen for the SASE3 undulator beamline, and indicate that one can achieve diffraction to the desired resolution with 15 mJ (corresponding to about 3·10¹³ photons) in pulses of about 3 fs, in the case of a 100 nm focus at the photon energy of 3.5 keV.

MOP058

Purified SASE Undulator Configuration to Enhance the Performance of the Soft X-ray Beamline at the European XFEL

undulator, FEL, radiation, laser

169

V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany

The purified SASE (pSASE) undulator configuration recently proposed at SLAC promises an increase in the output spectral density of XFELs. In this article we study a straightforward implementation of this configuration for the soft x-ray beamline at the European XFEL. A few undulator cells, resonant at a subharmonic of the FEL radiation, are used in the middle of the exponential regime to amplify the radiation, while simultaneously reducing the FEL bandwidth. Based on start-to-end simulations, we show that with the proposed configuration the spectral density in the photon energy range between 1.3 keV and 3 keV can be enhanced of an order of magnitude compared to the baseline mode of operation. This option can be implemented into the tunable-gap SASE3 baseline undulator without additional hardware, and it is complementary to the self-seeding option with grating monochromator proposed for the same undulator line, which can cover the photon energy range between about 0.26 keV and 1 keV.

MOP059

Beam Dynamic Simulations for Single Spike Radiation with Short-Pulse Injector Laser at FLASH

laser, simulation, operation, radiation

173

M. Rehders
University of Hamburg, Hamburg, Germany
J. Rönsch-Schulenburg
CFEL, Hamburg, Germany
J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
S. Schreiber
DESY, Hamburg, Germany

Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper discusses the generation of single spike SASE pulses at soft x-ray wavelength at the free-electron laser FLASH by using very short electron bunches of only a few micrometer bunch length. In order to achieve these extremely short bunch lengths, very low bunch charges (in the order of 20 pC) and short electron bunches exiting the photo-injector are required. For this, a new short-pulse injector laser with adjustable rms pulse duration in the range of 0.7 ps to 1.6 ps and bunch charges up to 200 pC was installed, extending the electron beam parameter range before bunch compression in magnetic chicanes. Beam dynamic studies have been performed to optimize the injection and compression of low-charge electron bunches by controlling the effect of coherent synchrotron radiation and space-charge induced bunch lengthening and emittance growth. Optimization includes the pulse parameters of the injector laser. The simulation codes ASTRA, CSRtrack and Genesis 1.3 were employed.

MOP060

Demonstration of SASE Suppression Through a Seeded Microbunching Instability

laser, undulator, FEL, free-electron-laser

177

C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, E. Hass, K. Honkavaara, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov
DESY, Hamburg, Germany
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school 1355.
Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.

MOP061

Electron Beam Delays for Improved Temporal Coherence and Short Pulse Generation at SwissFEL

undulator, FEL, radiation, simulation

181

N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Reiche
PSI, Villigen PSI, Switzerland

Proposals have been made for the introduction of magnetic electron beam delays in between the undulator modules of a long sectional FEL undulator - these can be used for the generation of trains of FEL pulses which can individually be shorter than the FEL cooperation time [*] or to greatly improve the temporal coherence of the FEL output compared to the nominal SASE configuration [**,***,***]. This paper comprises a feasibility study of the application of these techniques to the SwissFEL hard X-Ray beamline. Three-dimensional simulations are used to investigate the potential photon output.
[*] N.R. Thompson and B.W.J. McNeil, PRL 100:203901, 2008.
[**] N.R. Thompson et al. In Proc IPAC2010, pages 2257–2259, 2010
[***] J. Wu, A. Marinelli, and C. Pellegrini. Proc FEL2012, 2012.

MOP063

A Novel Modeling Approach for Electron Beams in SASE FELs

radiation, FEL, target, operation

190

P. Niknejadi, J. Madey
University of Hawaii, Honolulu,, USA

We have recently shown that the Wheeler-Feynman analysis of the interaction of a moving charge with distant absorbers [*] provides a perfect match to the energy radiated by two coherently oscillating charged particles (a heretofore unsolved problem in classical electrodynamics) [**]. Here we explain the need to include the Wheeler-Feynman coherent radiation reaction force as an integral part of the solution of the boundary value problem of free electron lasers (FELs) that radiate into “free space”. We will also discuss how the advanced field of the absorber can interact with the radiating particles at the time of emission. Finally we will introduce and explore the possibility of improving the temporal coherence in the self amplified spontaneous emission (SASE) FELs as well as the possibility of optimizing the spectrum of the emitted coherent radiation by SASE FELs via altering the structure of their targets by including the Wheeler-Feynman coherent radiation reaction force in the analysis of FEL operations.
* Wheeler, J. A.; Feynman, R. P, Rev. Mod. Phys. 17, 157, 1945.
** P. Niknejadi et al. "Energy Conservation of Coherently Oscillating Charged Particles in Classical Electrodynamics" submitted.

MOP065

Optimization of a High Efficiency FEL Amplifier

undulator, FEL, radiation, laser

199

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

The problem of an efficiency increase of an FEL amplifier is now of great practical importance. Technique of undulator tapering in the post-saturation regime is used at the existing x-ray FELs LCLS and SACLA, and is planned for use at the European XFEL, Swiss FEL, and PAL XFEL. There are also discussions on the future of high peak and average power FELs for scientific and industrial applications. In this paper we perform detailed analysis of the tapering strategies for high power seeded FEL amplifiers. Application of similarity techniques allows us to derive universal law of the undulator tapering.

MOP066

An Overview of the Radiation Properties of the European XFEL

radiation, operation, undulator, hardware

204

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

We present an overview of the radiation properties of the European XFEL based on recently accepted strategy of operation at the fixed set of electron energies (8.5 GeV, 12 GeV, 14 GeV, and 17.5 GeV), baseline parameters if the electron beam, and new set undulator parameters. We also discuss potential extension of the parameter space which does not require new hardware and can be realized at a very early stage of the European XFEL operation.

MOP067

Prospects for CW Operation of the European XFEL in Hard X-ray Regime

linac, undulator, operation, FEL

210

R. Brinkmann, E. Schneidmiller, J.K. Sekutowicz, M.V. Yurkov
DESY, Hamburg, Germany

The European XFEL will operate nominally at 17.5 GeV in SP (short pulse) mode with 0.65 ms long bunch train and 10 Hz repetition rate. A possible upgrade of the linac to CW (continuous wave) or LP (long pulse) modes with a corresponding reduction of electron beam energy is under discussion since many years. Recent successes in the dedicated R&D program allow to forecast a technical feasibility of such an upgrade in the foreseeable future. One of the challenges is to provide sub-Angstroem FEL operation in CW and LP modes. In this paper we perform a preliminary analysis of a possible operation of the European XFEL in the hard X-ray regime in CW and LP modes with the energies of 7 GeV and 10 GeV, respectively. We consider lasing in the baseline XFEL undulator as well as in a new undulator with a reduced period. We show that, with reasonable requirements on electron beam quality, lasing on the fundamental will be possible in sub-Angstroem regime. As an option for generation of brilliant photon beams at short wavelengths we also consider harmonic lasing that has recently attracted a significant attention.

MOP068

Suppression of the Fundamental Frequency for a Successful Harmonic Lasing in SASE FELs

undulator, FEL, simulation, photon

215

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Harmonic lasing in X-ray FELs has recently attracted a significant attention and is now seriously considered as a potential method for generation of brilliant photon beams at short wavelengths. It is clear, however, that for a successful harmonic lasing one has to suppress the fundamental. In this paper we discuss different methods for such a suppression: phase shifters, intraundulator spectral filtering, switching between the 3rd and the 5th harmonics etc.

MOP070

Design Study for the PEHG Experiment at SDUV-FEL

FEL, experiment, bunching, simulation

219

C. Feng, H.X. Deng, B. Liu, D. Wang, X.T. Wang, M. Zhang, T. Zhang, W. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

Funding: This work was partially supported by National Natural Science Foundation of China (11475250, 11175240 and 11205234)
In this paper, design studies for the proof-of-principle experiment of the recently proposed phase-merging enhanced harmonic generation (PEHG) mechanism are presented. A dogleg and a new designed transverse gradient undulator should be added in the undulator system of SDUV-FEL to perform the phase-merging effect. With the help of 3D simulation codes, we show the possible performance of PEHG with the realistic parameters of SDUV-FEL.
* H. Deng, C. Feng, Phys. Rev. Lett. 111, 084801.
** C. Feng, H. Deng, D. Wang, Z. Zhao, New J. Phys.,16, 043021.
*** C. Feng, T. Zhang, H. Deng, Z. Zhao, Phys. Rev. ST Accel. Beams 17, 070701.

MOP075

Laser Seeding Schemes for Soft X-rays at LCLS-II

undulator, laser, bunching, radiation

223

G. Penn
LBNL, Berkeley, California, USA
P. Emma, E. Hemsing, G. Marcus, T.O. Raubenheimer, L. Wang
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515.
The initial design for LCLS-II incorporates both SASE and self-seeded configurations. Increased stability and/or coherence than is possible with either configuration may be provided by seeding with external lasers followed by one or more stages of harmonic generation, especially in the soft x-ray regime. External seeding also allows for increased flexibility, for example the ability to quickly vary the pulse duration. Studies of schemes based on high-gain harmonic generation and echo-enabled harmonic generation are presented, including realistic electron distributions based on tracking through the injector and linac.

MOP077

Measurements of the FEL-bandwidth Scaling with Harmonic Number in a HGHG FEL

FEL, laser, operation, experiment

227

E. Allaria, M.B. Danailov, W.M. Fawley, E. Ferrari, L. Giannessi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy

In this work we report recent measurements done at FERMI showing the dependence of the FEL bandwidth with respect to the seed laser harmonic at which the FEL is operated. Comparison of FEL spectra for different Fourier-limit seed and chirp pulses is also reported.

MOP078

Measurements of FEL Polarization at FERMI

polarization, FEL, experiment, radiation

231

E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

We report detailed quantitative characterization of different polarization states of a single-pass, externally-seeded FEL operating with variable polarization undulators in the VUV spectral range. The experiment has been performed at FERMI FEL-1 operated in the 52–26 nm wavelength range. Three different, independent polarimeter setups, installed at the end of ex- perimental beamlines, have been used to characterize the four “pure” polarization states: horizontal, vertical, right-circular and left-circular. The impact of downstream transport optics upon the radia- tion polarization has been assessed; at longer wavelengths, dichroism effects lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other and allow a cross-calibration of the instruments.
On behalf of the team organized for polarization measurements at FERMI.

MOP079

Generation of Multiple Coherent Pulses in a Superradiant Free-Electron Laser

FEL, radiation, undulator, simulation

233

X. Yang, S. Seletskiy
BNL, Upton, Long Island, New York, USA
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy

We analyze the structure of the tail of a superradiant pulse, which is constituted by a train of sub-pulses with decaying amplitudes. We show how a trailing pulse, with pi phase advance from the leading pulse, is generated at the falling edge of the leading superradiant pulse, where the corresponding phase space is deeply saturated and the electrons become de-trapped by the reduced ponderomotive potential. Once the trailing pulse gains enough energy, it generates a second trailing pulse, and the process takes place again. By performing detailed simulations of the resulting electron phase space distribution and the FEL pulse spectral and temporal structure with PERSEO, we confirm that the deformation and re-bunching of the longitudinal phase space create a sequence of pulses. These results are compared to 3D simulations using the FEL code GENESIS 1.3 showing a good agreement.

MOP082

Perspectives for Imaging Single Protein Molecules with the Present Design of the European XFEL

photon, laser, free-electron-laser, FEL

238

G. Geloni
XFEL. EU, Hamburg, Germany
V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
O. Yefanov
CFEL, Hamburg, Germany

European XFEL aims to support imaging and structure determination of biological specimens between less than 0.1 microns and 1 micron size with working photon energies between 3 keV and 16 keV. This wide operation range is a cause for challenges to the focusing optics. A long propagation distance of about 900 m between x-ray source and sample leads to a large lateral photon beam size at the optics. Due to the large divergence of nominal X-ray pulses with durations shorter than 10 fs, one suffers diffraction from mirror apertures, leading to a 100-fold decrease in fluence at photon energies around 4 keV, which seem ideal for imaging of single biomolecules. Moreover, the nominal SASE1 is very far from the level required for single particle imaging. Here we show how it may be possible to optimize the SPB instrument for single biomolecule imaging with minimal additional costs and time, achieving diffraction without destruction at near-atomic resolution with 10¹³ photons in a 4 fs pulse at 4 keV photon energy and in a 100 nm focus, corresponding to a fluence of 10²³ ph/cm². This result is exemplified using the RNA Pol II molecule as a case study.

MOP083

Start-to-End Simulation for FLASH2 HGHG Option

simulation, undulator, radiation, FEL

244

G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov
DESY, Hamburg, Germany
K.E. Hacker
DELTA, Dortmund, Germany
T. Plath
Uni HH, Hamburg, Germany

The Free-electron laser in Hamburg (FLASH) is the first FEL user facility to have produced extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade of FLASH named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections, a seeding undulator section and a SASE undulator section. In this paper, results from a start-to-end simulation for a FLASH2 High-Gain Harmonic Generation (HGHG) option are presented. For the beam dynamics simulation, space charge, coherent synchrotron radiation (CSR) and longitudinal cavity wake field effects are taken into account. In order to get electron beam bunches with small correlated and uncorrelated energy spread, RF parameters of the accelerating modules have been optimized as well as the parameters of the bunch compressors. Radiation simulations for the modulator and the radiator have been done with code Genesis 1.3 by using the particle distribution generated from the beam dynamics simulation. The results show that for a single stage HGHG, 33.6 nm wavelength FEL radiation can be seeded at FLASH2 with a 235 nm seeding laser.

MOP084

Enhancing Coherent Harmonic Generation using Tilted Laser Wavefronts

laser, radiation, synchrotron, synchrotron-radiation

248

S. Khan
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (contract 05K13PE3)
Coherent Harmonic Generation (CHG) to produce ultrashort pulses of synchrotron radiation is based on the interaction of relativistic electrons in a storage ring with femtosecond laser pulses in an undulator. The resulting periodic energy modulation can be converted to a density modulation by a dispersive chicane, giving rise to coherent emission at harmonics of the laser wavelength in a second undulator. If the first undulator is in a section with non-zero dispersion, the density modulation can be enhanced using tilted laser wavefronts, thus delaying the phase-space distributions of electrons with different energy with respect to each other. The most simple way to realize the wavefront tilt would be to introduce a small crossing angle between the electron and laser beam. Details are discussed for the case of the CHG short-pulse facility at DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, but HGHG and EEHG seeding of free-electron lasers could also be performed this way.

MOP086

Broadly Tunable THz FEL Amplifier

FEL, laser, undulator, radiation

252

C.H. Chen, F.H. Chao, Y.C. Chiu, Y.K. Gan, K.Y. Huang, Y.-C. Huang, Y.C. Wang
NTHU, Hsinchu, Taiwan

Funding: MOST 102-2112-M-007 -002 -MY3, Taiwan
In this paper we present a broadly tunable sub-MW THz FEL amplifier driven by a photoinjector with a sub-kW seed THz source tunable between 0.7-2.0 THz. Specifically an S-band photoinjector at 2.856 GHz generate a 3.3-5.5 MeV electron bunch with 0.5 nC charge in a 4.25 ps rms bunch length, which is injected into a 2-m long undulator with a period of 18 mm and an rms undulator parameter of 0.98. The driver laser of the photoinjector is a frequency quadrupled amplified, mode-locked Nd:YVO4 laser at 1064 nm. We recycle the unconverted infrared laser at 1064 nm to pump a THz parametric amplifier using a lithium niobate crystal as its gain crystal. This THz parametric amplifier generates a transform-limited THz pulse with sub-kW power between 0.7 and 2.0 THz, which is seeded into the undulator to produce broadly tunable, transform-limited, sub-MW THz radiation through FEL amplification with a gain of about 3000. Since the pump laser of the THz OPA is derived from the driver laser of the photoinjector, the seed THz pulse is fully synchronized and overlapped with the electron bunch. Experimental progress of this work will be presented in the conference.
*Work supported by MoST under NSC 102-2112-M-007-002-MY3

Poster MOP086 [1.269 MB]

MOP087

Upgrade Plans for the Short-pulse Facility at DELTA

laser, undulator, radiation, dipole

255

S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
DELTA is a 1.5-GeV synchrotron light source operated by the TU Dortmund University with a short-pulse facility based on Coherent Harmonic Generation (CHG) * to produce radiation with wavelengths in the VUV regime. Even shorter wavelengths can be generated by an upgrade based on the Echo-Enabled Harmonic Generation (EEHG) technique ** which requires additional magnetic chicanes and undulators. A new storage ring lattice provides enough free space for an EEHG setup and additionally for a femtoslicing undulator. Besides the new optics, first simulation results of EEHG will be presented.
* S. Khan et al., Sync. Rad. News 26, 3 (2013).
** G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).

MOP088

High Repetition Rate Energy Modulator System Utilizing a Laser Enhancement Cavity

laser, cavity, radiation, resonance

260

Y. Honda
KEK, Ibaraki, Japan

A high intensity laser field can be realized at a high repetition rate using an enhancement optical cavity scheme. We propose to apply the 100GW-level laser field inside the cavity for producing a micro-bunch structure in an electron bunch. Combining this system with an ERL scheme of accelerator, it can be used for a seeded FEL at a high repetition rate of ~100MHz continuous beam. The longitudinal electric field at the center area of a higher-order transverse mode of laser can be used to modulate beam energy at a period of the laser wavelength. A 250 MeV class two-loop ERL accelerator has been proposed in KEK as a future upgrade plan of existing 35 MeV ERL test accelerator. It will be able to provide a low emittance, small energy spread, short bunch electron beam at a high repetition rate of continuous operation. We propose to apply this beam to produce a seeded VUV coherent radiation. We will discuss the feasibility of the scheme and status of the laser modulator development.

MOP092

X-ray Monochromators for Self-seeding XFELs in the Photon Energy Range Starting from 1.5 keV

photon, FEL, scattering, radiation

269

Yu. Shvyd'ko
ANL, Argonne, Ilinois, USA

Self-seeding of XFELs below 1 keV can be performed using grating monochromators [1]. Forward-Bragg diffraction (wake) monochromators [2] were instrumental for achieving self-seeding in hard x-ray FELs in the photon energy range from 5 to 10 keV [3]. Large photo-absorption makes extension into the lower photon range difficult. Here alternative schemes of x-ray monochromators are introduced and discussed for achieving self-seeding in a yet inaccessible spectral range starting from 1.5 keV.
[1] J. Feldhaus, et al., Opt. Commun. 140, 341 (1997).
[2]. G. Geloni, V. Kocharyan, and E. Saldin, J. Mod. Opt. 58, 1391 (2011).
[3] J. Amann, et al., Nat. Photonics 6, 693 (2012).

MOP094

Indirect Measurements of NIR and UV Ultrashort Seed Laser Pulses using a Transverse Deflecting RF-Structure

laser, undulator, experiment, interaction-region

272

N. Ekanayake, S. Ackermann
DESY, Hamburg, Germany
S. Ackermann, C. Lechner, Th. Maltezopoulos, T. Plath
Uni HH, Hamburg, Germany
K.E. Hacker
DELTA, Dortmund, Germany

Seeding of free-electron lasers (FELs) using external coherent optical pulses recently became an area of interest as users demand spectrally and temporally coherent FEL radiation which is not achievable in traditional self-amplified spontaneous emission operation mode. Since temporal and spectral properties of the seed laser pulses are directly imprinted on the electron bunch, a proper characterization of these seed pulses is needed. However, the lack of any measurement technique capable of characterizing ultrashort seed laser pulses at the laser-electron interaction region is a primary drawback. In this paper we report indirect measurements of seed laser pulses in an undulator section using a transverse deflecting RF-structure (TDS-LOLA) at the free-electron laser FLASH at DESY. Temporally chirped and unchirped seed pulse length measurements will be compared with second-harmonic generation frequency-resolved optical gating measurements and theoretical simulations. Using this technique we will demonstrate that pulse artifacts such as pre- and post-pulses in the seed pulse in the femtosecond and picosecond timescales can be identified without any temporal ambiguity.
Authors acknowledge the support received from FLASH team and many groups at DESY in preparation and commissioning of experiments. We thank our colleagues in the FLASH seeding team for their support.

MOP095

HGHG AND EEHG MICROBUNCHES WITH CSR AND LSC

simulation, FEL, dipole, radiation

275

K.E. Hacker
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (contract 05K13PE3) and DESY
Longitudinal space charge (LSC) forces in a drift and coherent synchrotron radiation (CSR) in a chicane are relevant for high gain harmonic generation (HGHG) and echo enabled harmonic generation (EEHG) seeding designs. These factors determine whether or not the modulator can be located significantly upstream of the radiator. The benefits and dangers of having a drift in between the radiator and the modulator are investigated and a measurement of the LSC enabled reduction of the energy spread of a seeded beam is presented.

MOP096

Enhancing the Harmonic Content of an HGHG Microbunch

laser, undulator, simulation, bunching

281

K.E. Hacker
DELTA, Dortmund, Germany

Funding: BMBF grant 05K10PE1 and DESY
High Gain Harmonic Generation (HGHG) seeding has been demonstrated in the visible and ultraviolet, but it is limited in performance at high harmonics of the seed by the initial uncorrelated energy spread of the electron beam. A recent proposal from SINAP using a chirped electron beam and a canted pole undulator has suggested a new mechanism for cooling the uncorrelated energy spread of the electron beam in order to improve the performance of HGHG seeding at high harmonics. This note reviews the mechanism, the limitation of the concept and extrapolates to some new concepts using analogous mechanisms derived from transverse gradients of the laser properties. The impact of CSR wakes on the vanishingly short microbunches produced by the methods are also investigated.
[1] H. Deng and C. Feng, Phys. Rev. Lett. 111, 084801 (2013)

MOP097

A Concept for Seeding 4-40 nm FEL Radiation at FLASH2

laser, FEL, bunching, undulator

286

K.E. Hacker
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (contract 05K13PE3)
This note describes a scheme to seed the FLASH2 FEL over a range of 4-40 nm without impacting SASE capabilities. This scheme combines multiple seeding techniques, builds on current infrastructure and offers a maximized range of performance with higher pulse energies than what are available at lower-peak current facilities. The concept relies on Echo Enabled Harmonic Generation (EEHG), cascaded seeding, and Second Harmonic Afterburners (SHAB) while maintaining the possibility to operate with High Gain Harmonic Generation (HGHG) seeding at >30 nm wavelengths.

MOC01

Circular Polarization Control by Reverse Undulator Tapering

FEL, undulator, resonance, bunching

297

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

In order to produce circularly polarized light at X-ray FEL facilities one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. We propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. The method can be used at different X-ray FEL facilities, in particular at LCLS after installation of the helical afterburner in the near future.

Slides MOC01 [1.545 MB]

MOC03

Radiation Properties of Tapered Hard X-ray Free Electron Lasers

radiation, FEL, undulator, simulation

300

C. Emma, C. Pellegrini
UCLA, Los Angeles, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
K. Fang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S. Serkez
DESY, Hamburg, Germany

We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.

Slides MOC03 [3.797 MB]

MOC04

Chirped and Modulated Electron Pulse Free Electron Laser Techniques

undulator, radiation, FEL, simulation

303

J. Henderson, L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom

Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20
A potential method to improve the free electron laser's output when the electron pulse has a large energy spread is investigate and results presented. A simplified model is the first given, in which there are a number of linearly chirped beamlets equally separated in energy and time. By using chicanes, radiation from one chirped beamlet is passed to the next, helping to negate the effect of the beamlet chirps and maintaining resonant interactions. Hence the addition of chicane allow the electrons to interact with a smaller range of frequencies (Δ ω <2 ρ γ_r), sustaining the FEL interaction. One method to generate such a beamlet structure is presented and is shown to increase FEL performance by two orders of magnitude.

Slides MOC04 [6.777 MB]

TUA02

A Review of High Power OPCPA Technology for High Repetition Rate Free-Electron Lasers

laser, operation, FEL, free-electron-laser

310

M.J. Prandolini, R. Riedel
HIJ, Jena, Germany
M. Schulz
DESY, Hamburg, Germany
F. Tavella
SLAC, Menlo Park, California, USA

High repetition rate free-electron lasers (FEL) require the development of new laser systems that have the ability to operate at high average power. Optical parametric chirped-pulse amplification (OPCPA) is presently the most promising method to fulfill these requirements. This technique has been used to demonstrate amplification up to tens of watts with a repetition rate in the range between tens of kHz to MHz in burst and continuous mode. We review the current OPCPA technology for systems operating around 800 nm; this includes various frontend options, pump amplifier technology and latests results, and we discuss the important requirements for achieving high power lasers in both burst and continuous operation.
Work supported by the Helmholtz Institute Jena and the Deutsches Elektronen-Synchrotron DESY in Hamburg.

Slides TUA02 [4.997 MB]

TUA04

Status of the SwissFEL C-band Linac

linac, klystron, network, free-electron-laser

322

F. Löhl, J. Alex, H. Blumer, M. Bopp, H.-H. Braun, A. Citterio, U. Ellenberger, H. Fitze, H. Jöhri, T. Kleeb, L. Paly, J.-Y. Raguin, L. Schulz, R. Zennaro, C. Zumbach
PSI, Villigen PSI, Switzerland

The linear accelerator of SwissFEL will be based on C- band technology. This paper summarizes the latest results that were achieved with the first prototype components. Fur- thermore, the progress and plans of the series production are discussed.

Slides TUA04 [11.482 MB]

TUB01

Review of Coherent SASE Schemes

undulator, FEL, bunching, experiment

327

B.W.J. MᶜNeil, L.T. Campbell, J. Henderson
USTRAT/SUPA, Glasgow, United Kingdom
D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: We acknowledge STFC Agreement No. 4163192; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Julich Supercomputing Centre (JSC), project HHH20
A review is presented of some of the methods and their origins that have recently been proposed to improve the temporal coherence of SASE output. These methods do not require any external laser seed field, or the use of the so-called self-seeding methods, where the SASE radiation is optically filtered and improved at an early stage of the interaction before re-injection and amplification to saturation. By using methods that introduce an additional relative propagation between the electron beam and the radiation field, the localised collective interaction, which leads to the formation of the ‘spiking’ associated with normal SASE output, is removed. The result is output pulses which are close to the fourier transform limit without the need for any external seeds or intermediate optics.

Slides TUB01 [6.256 MB]

TUB02

Generation of Intense XVUV Pulses with an Optical Klystron Enhanced Self- amplified Spontaneous Emission Free Electron Laser

FEL, klystron, laser, radiation

332

G. Penco, E. Allaria, G. De Ninno, E. Ferrari, L. Giannessi
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. De Ninno
University of Nova Gorica, Nova Gorica, Slovenia
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy

Fermi is a seeded FEL operating in high gain harmonic generation mode. The FEL layout is constituted by a modulator and six radiators separated by a dispersive section. The modulator and the radiators can be tuned to the same resonant frequency to set up an asymmetric optical klystron configuration where self amplified spontaneous emission can be generated and studied. This paper presents the experiment consisting in the analysis of the enhancement of the self-amplified spontaneous emission (SASE) radiation by the dispersion in the optical klystron. The FEL pulses produced with the optical klystron configuration are several order of magnitude more intense than in pure SASE mode with the dispersion set to zero, The experimental observations are in good agreement with simulation results and theoretical expectations. A comparison with the typical high-gain harmonic generation seeded Fel operation is also provided.

Slides TUB02 [12.835 MB]

TUB03

FEL Overcompression in the LCLS

simulation, experiment, FEL, diagnostics

337

J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk.

Slides TUB03 [4.493 MB]

TUB04

Operation of FLASH with Short SASE-FEL Radiation Pulses

laser, FEL, operation, free-electron-laser

342

J. Rönsch-Schulenburg, E. Hass, N.M. Lockmann, T. Plath, M. Rehders, J. Roßbach
Uni HH, Hamburg, Germany
G. Brenner, S. Dziarzhytski, T. Golz, H. Schlarb, B. Schmidt, E. Schneidmiller, S. Schreiber, B. Steffen, N. Stojanovic, S. Wunderlich, M.V. Yurkov
DESY, Hamburg, Germany

Funding: The project has been supported by the Federal Ministry of Education and Research of Germany (BMBF) under contract No. 05K10GU2 and FSP301
This paper describes the experimental activity on the generation of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-electron laser FLASH [1, 2]. The key element, a photo-injector laser which is able to generate laser pulses of about 2 ps FWHM has been optimized and commissioned. It allows the generation of shorter bunches with low bunch charge (of up to 200 pC) directly at the photo-cathode. Initially shorter injector laser pulses and thus shorter bunches eases the required bunch compression factor for short pulses below 10 fs duration which makes operation of the electron beam formation system to be more robust with respect to jitters and collective effects. As a result, overall stability of SASE FEL performance is improved. In the optimal case single-spike operation can be achieved. In this paper the experimental results on production of short electron bunches and the SASE performance using the new injector laser will be shown and the measured electron bunch and FEL radiation properties are discussed. In addition, optimizations of bunch diagnostics for low charge and short bunches are discussed.

Slides TUB04 [1.201 MB]

TUP002

Characterization of Partially Coherent Ultrashort FEL Pulses

FEL, laser, free-electron-laser, photon

346

C. Bourassin-Bouchet, M.-E. Couprie
SOLEIL, Gif-sur-Yvette, France
C. Evain
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France

Temporal metrology is a major need for free-electron lasers. However, the lack of longitudinal coherence, that is shot-to-shot fluctuations, of these sources has prevented so far the full amplitude and phase temporal characterization of FEL pulses. To sort out this issue, we propose a solution inspired from attosecond metrology, where XUV pulse measurement techniques already exist, and from coherent diffraction imaging, where numerical solutions have been developed for processing partially coherent diffraction patterns. The experimental protocole implies the measurement of photoelectron spectra obtained through XUV-laser photoionisation. The spectra are then processed with an algorithm in order to retrieve the partially coherent FEL pulse. When applied to SASE FELs, the technique gives access to the full statistics of the emitted pulses. With seeded-FELs, the pulse shape becomes stable from shot-to-shot, but an XUV-laser time jitter remains. In that case, the technique enables the joint measurement of the FEL pulse shape (in amplitude and phase) and of the laser/FEL jitter envelope. The concept has been validated with numerical simulations in the context of the LUNEX5 FEL project.

TUP003

Quantum FEL II: Many-electron Theory

FEL, laser, resonance, photon

348

P. Kling, R. Sauerbrey
HZDR, Dresden, Germany
R. Endrich, E.A. Giese, W.P. Schleich
Uni Ulm, Ulm, Germany

We investigate the emergence of the quantum regime of the FEL when many electrons interact simultaneously with the wiggler and the laser field. We find the Quantum FEL as the limit where only two momentum states are populated by the electrons. Moreover, we obtain exponential gain-per-pass and start-up from vacuum.

TUP004

Quantum FEL I: Multi-mode Theory

photon, resonance, coupling, FEL

353

R. Endrich, E.A. Giese, W.P. Schleich
Uni Ulm, Ulm, Germany
P. Kling, R. Sauerbrey
HZDR, Dresden, Germany

The quantum regime of the FEL in a single-mode, single-particle approximation is characterized by a two-level behaviour of the center-of-mass motion of the electrons. We extend this model to include all modes of the radiation field and analyze the effect of spontaneous emission. In particular, we investigate this scattering mechanism to derive experimental conditions for realizing an FEL in the quantum regime.

TUP006

Two-color Free-electron Laser via Two Orthogonal Undulators

FEL, polarization, undulator, radiation

358

N.S. Mirian
IPM, Tehran, Iran
G. Dattoli
ENEA C.R. Frascati, Frascati (Roma), Italy
V. Petrillo
Universita' degli Studi di Milano, Milano, Italy

An amplifier Free electron Laser (FEL) including two orthogonal polarized undulators with different periods and field intensities is able to emit two color radiations with different frequency and polarization while the total length of device does not change respect to usual single color FELs. The wavelengths of two different colors can be changed by choosing different periods, while variation in the magnetic strengths can be used to modify the gain lengths.

TUP007

Spectral Limits and Frequency Sum-rule of Current and Radiation Noise Measurement

radiation, distributed, undulator, FEL

362

A. Gover, R. Ianconescu
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
A. Nause
UCLA, Los Angeles, USA

Funding: This research was supported by a grant from the United States-Israel Binational Science Foundation(BSF), Jerusalem, ISRAEL
The current noise spectrum of an electron beam is generally considered white and expressed by the shot-noise formula (eI0). It is possible to control the spectral energy of a random electron beam current by longitudinal space charge microdynamics and dispersive transport. Both noise suppression (relative to eI0)[1,2] and noise enhancement[3] have been demonstrated, exhibiting sub/super-Poissonian particle distribution statistics, respectively. We present a general theory for the current noise of an e-beam and its radiation emission in the entire spectrum. The measurable current noise spectrum is not white. It is cut-off at high frequencies, limited by the measurement length and the beam axial momentum spread (fundamentally limited by quantum uncertainty). We show that under certain conditions the current noise spectrum satisfies a frequency sum-rule: exhibiting noise enhancement in one part of the spectrum when suppressed at another part and vice versa. The spontaneous emission (radiation noise) into a single radiation mode or single direction in any scheme (OTR, Undulator etc.) is sub-radiant when the beam current is sub-Poissonian and vice versa, but the sum-rule does not apply.

TUP008

An Analysis of Optimum Out-coupling Fraction for Maximum Output Power in Oscillator FEL

coupling, FEL, cavity, laser

368

Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

The effect of the out-coupling fraction on the output power in oscillator FEL is analyzed. The formulas of the optimum out-coupling fraction and the corresponding maximum output power are given. They are dependent on the initial small signal gain and the passive loss rate of the light in the optical cavity. The initial comparison show that the result given by the formula agree well with the results in references.

TUP009

A Simple Method for Generating a Few Femtosecond Pulses in Seeded FELs

laser, FEL, radiation, linac

371

H.T. Li, Z.G. He, Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by Major State Basic Research Development Program of China (2011CB808301) and the Fundamental Research Funds for the Central Universities of China (WK2310000045)
We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the centre part of electron beam and short pulses in high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse with duration of 8 femtoseconds (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 m.

TUP012

Numerical Simulation of a Super-radiant THz Source Driven by Femtosecond Electron Bunches

undulator, FEL, radiation, emittance

374

R.V. Chulkov
B.I. Stepanov Institute of Physics, Belarus, Russia
V.A. Goryashko
Uppsala University, Uppsala, Sweden
V. Zhaunerchyk
University of Gothenburg, Gothenburg, Sweden

Funding: We would like to acknowledge the financial support from the Swedish FEL center.
Pulsed THz FELs are typically driven by rf Linacs which produce intense electron bunches with a duration of a few picoseconds or even shorter. When the bunch duration is less than a picosecond, the wavelength of the THz light is greater than the bunch length and the FEL operates in the super-radiant (SR) regime*. In the report, we summarize our studies performed for an SR source operating in the THz frequency range. In particular, we focus on an open-type planar undulator comprising no guiding structure. Using a numerical code that supports 3D modeling of the SR dynamics as well as statistical properties of electron bunches, we analyze influence of electron bunch parameters on generated THz radiation and reveal some surprising results. More specifically, for the considered undulator configuration, we predict degradation in the angular divergence and spectral broadening of the generated radiation as the electron bunch emittance decreases. We also demonstrate how electron bunch broadening associated with the electron energy spread can eventually be suppressed.
* R. Chulkov, V. Goryashko, and V. Zhaunerchyk, Report III of the series of reports by the Swedish FEL Center and FREIA Group, http://www.diva-portal.org/smash/get/diva2:699684/FULLTEXT01.pdf.

Poster TUP012 [1.553 MB]

TUP013

X-Ray Smith-Purcell Radiation from a Beam Skimming a Grating Surface

radiation, target, factory, free-electron-laser

378

D.Yu. Sergeeva, A.A. Tishchenko
MEPhI, Moscow, Russia

Smith-Purcell radiation as a base of Free Electron Lasers is actively studied experimentally and by simulating. Usually the beam is supposed to move at some distance above the target. In practice the distance is tried to decrease so that the beam passes very close to the target surface. Experimental data contains the information about grating heating. The authors of article* suggested the cause of the heating is that the beam skims the grating surface. Developing the method used in**,*** we give the analytical description of the X-Ray radiation arising when the beam of charge particles moves parallel above the periodical target, but the part of the beam crosses the target. The radiation arising is the superposition of Smith-Purcell radiation and transition radiation from the grating. This radiation determines the process of beam bunching and following gain of radiation.
*H.L.Andrews et al,Phys. Rev. ST AB 12 (2009) 080703
**A.A.Tishchenko, A.P.Potylitsyn, M.N.Strikhanov, Phys. Rev. E 70 (2004) 066501
***D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189

TUP014

Forward X-Ray and Ultraviolet Smith-Purcell Radiation for FEL

radiation, target, polarization, plasma

384

A.A. Tishchenko, D.Yu. Sergeeva
MEPhI, Moscow, Russia

The scheme of Free Electron Lasers based on Smith-Purcell effect is well known to describe the process of interaction between an electron beam and evanescent wave, which bunches this beam. In this work we concentrate on the process of generation of the radiation propagating at small angles. In terms of approach described in detail in*,**, we investigate the Smith-Purcell radiation at oblique incidence of a single charged particle for X-Ray and UV frequency region. This forward radiation propagates through all the region of the beam moving and provides more close interaction between the beam and the radiation, than usual surface waves existing in FELs. Spectral and angular characteristics of the forward radiation are discussed from point of view its role in Smith-Purcell based FELs.
*A.P.Potylitsyn, M.I.Ryazanov, M.N.Strikhanov, A.A.Tishchenko, Diffraction Radiation from Relativistic Particles, Springer, 2011
**D.Yu.Sergeeva, A.A.Tishchenko, M.N.Strikhanov, NIM B 309 (2013) 189

TUP015

Radiation and Interaction of Layers in Quasi-plane Electron Bunches Moving in Undulators

radiation, undulator, laser, free-electron-laser

388

N. Balal
Ariel University, Ariel, Israel
V.L. Bratman
IAP/RAS, Nizhny Novgorod, Russia

The model of radiating planes (1D radiating gas) consisting of electrons that oscillate and travel with a relativistic translational velocity allows one to develop a simple general theory describing a number of important effects of radiation in a undulator for dense electron bunches formed in photoinjector accelerators. Having based on this method and taking into account both Coulomb and radiation interactions of the planes with an arbitrary density, particle velocity distribution and energy chirp we have found analytically and numerically efficiency and frequency spectrum for coherent spontaneous radiation, including conditions for generation of minimum narrow and very broadband spectra. The developed theory has been applied for estimation of a powerful terahertz radiation source with a moderate energy of electrons.

TUP016

Quasi-optical Theory of Terahertz Superradiance from an Extended Electron Bunch

radiation, simulation, resonance, wakefield

391

N.S. Ginzburg, A. Malkin, A. Sergeev, V.Yu. Zaslavsky, I.V. Zotova
IAP/RAS, Nizhny Novgorod, Russia

Funding: This study was supported by the Russian Foundation for Basic Research (project no. 14-08-01180) and the Dynasty Foundation.
We consider superradiance of an extended relativistic electron bunch moving over a periodically corrugated surface for the generation of multi-megawatt terahertz pulses*. To study the above process we have developed a three-dimensional, self-consistent, quasi-optical theory of Cherenkov stimulated emission which includes a description of the formation of evanescent waves near the corrugated surface and its excitation by RF current induced in the electron bunch. Results obtained in the framework of a quasi-optical model were confirmed by direct CST STUDIO PIC simulations. There is a possibility of advancement towards still shorter wavelengths (infrared and optical), which can be achieved by decreasing the period of the diffraction gratings and increasing the density and energy of the particles in the electron bunches. Increase of coupling impedance can be obtained by using inclined incidence of electron bunch on corrugated surface (clinotron configuration).
Ginzburg N.S et al. Phys. Rev. Lett. 2013. V.110, Iss.18. 184801.

TUP017

Using Lorentz Transformations for Simulations of Wiggler Superradiance from the Picosecond Electron Bunches

undulator, simulation, radiation, scattering

395

A. Malkin, N.S. Ginzburg, A.A. Golovanov, I.V. Zotova
IAP/RAS, Nizhny Novgorod, Russia
V.P. Tarakanov
LPI, Moscow, Russia

Funding: This work was supported by Russian Foundation for Basic Research under Grant No 12-02-01152.
In this paper we present a theoretical analysis of superradiance (SR) from picosecond electron bunches wiggling in periodical undulator field based both on the method of averaged ponderomotive force and on a direct numerical PIC (particle-in-cell) simulation. Within both approaches the analysis takes place in the reference frame co-moving with electrons which allows simplifying the procedure of simulation significantly due to the fact that all the spatial scales including the radiation wavelength, the length of the beam and the length of the pump field pacet into which the undulator field is transformed are of the same order. We show that in the reference frame the SR effect can be interpreted as a formation of the distributed Bragg mirror in the bulk of the electron beam which is effectively reflecting (scattering) the pump wave. A possibility of generation of multimegawatt pulses in terahertz and far infrared wave ranges is demonstrated.

TUP018

Sensitivity Study of a Tapered Free-Electron Laser

FEL, emittance, undulator, free-electron-laser

399

A.W.L. Mak, F. Curbis, S. Werin
MAX-lab, Lund, Sweden

The output power of a free-electron laser (FEL) can be greatly enhanced by tapering the undulator line. In this work, a sensitivity study of a tapered FEL is presented. The study is conducted using the numerical simulation code GENESIS and a taper optimization method. Starting from a possible case for the future X-ray FEL at the MAX IV Laboratory in Lund, Sweden, a number of parameters are varied systematically and the impact on the FEL power is investigated. These parameters include the electron beam's initial energy, current, emittance, energy spread, as well as the seed radiation power.

TUP019

Update on the FEL Code Genesis 1.3

undulator, radiation, lattice, FEL

403

S. Reiche
PSI, Villigen PSI, Switzerland

The widely used time-dependent code Genesis 1.3 has been modified to address new needs of users worldwide. The existing limitation of tracking isolated slices of the FEL beam has been overcome by keeping the entire electron beam in memory, which is tracked as a whole through the undulator. This modification allows for additional features such as allowing particles to migrate into other slices or applying self-consistent wakefield and space charge models.

TUP020

MINERVA, a New Code to Model Free-Electron Lasers

FEL, undulator, experiment, simulation

408

H. Freund, P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA
P.J.M. van der Slot
Mesa+, Enschede, The Netherlands

Simulation codes modelling the interaction of electrons with an optical field inside an undulator are an essential tool for understanding and designing free-electron lasers (FELs). As there exists a large variety of FELs ranging from long-wavelength oscillators using partial wave guiding to soft and hard x-ray FELs that are either seeded or starting from noise, a simulation code should be capable of modelling this huge variety of FEL configurations. A new code under development, named MINERVA, will be capable of modelling such a large variety of FELs. The code uses a modal expansion for the optical field, e.g., a Gaussian expansion for free-space propagation, and an expansion in waveguide modes for propagation at long wavelengths, or a combination of the two for partial guiding at THz frequencies. MINERVA uses the full Newton-Lorentz force equation to track the particles through the optical and magnetic fields. To allow propagation of the optical field outside the undulator and interact with optical elements, MINERVA interfaces with the optical propagation code OPC to model oscillators. Here we describe the main features of MINERVA and give various examples of its capabilities.

TUP021

Recent Updates to the Optical Propagation Code OPC

diagnostics, FEL, undulator, free-electron-laser

412

P.J.M. van der Slot, K.J. Boller
Mesa+, Enschede, The Netherlands
P.J.M. van der Slot
CSU, Fort Collins, Colorado, USA

Funding: This research is supported in part by Office of Naval Research Global, grant number N62909-10-1-7151
In order to understand and design free-electron lasers (FELs), simulation codes modeling the interaction of electrons with a co-propagating optical field in the magnetic field of an undulator are essential. However, propagation of the optical field outside the undulator is equally important for evaluation of the optical field at the location of the application or to model FEL oscillators. The optical propagation code OPC provides such capabilities and can interface with FEL gain codes like GENESIS 1.3, MEDUSA and MINERVA. Here we present recent additions and modifications to the code that (i) improves the speed of the code and (ii) extends the modeling capabilities. These include amongst other, inline diagnostics that results in considerable faster runtimes, the ability to convert from free-space modes to guided modes (currently only cylindrical waveguides), and the possibility to determine the spectrum at each transverse location. The latter opens the possibility to include dispersion in the optical propagation. Finally, work is underway to support HDF5 to remain compatible with the upcoming new release of GENESIS 1.3.

TUP022

The Implementation of 3D Undulator Fields in the Unaveraged FEL Simulation Code Puffin

undulator, FEL, focusing, simulation

416

J. Henderson, L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
A.R. Maier
CFEL, Hamburg, Germany
A.R. Maier
Uni HH, Hamburg, Germany

Funding: We acknowledge STFC MoA 4132361; ARCHIE-WeSt HPC, EPSRC grant EP/K000586/1; John von Neumann Institute for Computing (NIC) on JUROPA at Jlich Supercomputing Centre (JSC), under project HHH20
The FEL simulation code Puffin is modified to include 3D magnetic undulator fields. Puffin, having previously used a 1D undulator field, is modified to accommodate general 3D magnetic fields. Both plane and curved pole undulators have been implemented. The electron motion for both agrees with analytic predictions.

TUP025

TW X-ray Free Electron Laser Optimisation by Transverse Pulse Shaping

FEL, radiation, undulator, simulation

425

C. Emma, C. Pellegrini
UCLA, Los Angeles, USA
C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA

We study the dependence of the peak power of a 1.5 Angstrom TW, tapered X-ray free-electron laser on the transverse electron density distribution. Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of 1.5 Angstrom using the fully 3-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30-70 % reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian.

TUP026

Transverse Coherence Properties of a TGU-based FEL

FEL, undulator, radiation, emittance

429

P. Baxevanis, Z. Huang, R.D. Ruth
SLAC, Menlo Park, California, USA
C.B. Schroeder
LBNL, Berkeley, California, USA

The use of a transverse gradient undulator (TGU) is considered an attractive option for FELs driven by electron beams with a relatively large energy spread. In this scheme, a dispersion is introduced in the beam while the undulator poles are inclined so that the undulator field acquires a linear dependence upon the transverse position in the direction of dispersion. By suitably selecting the dispersion and the field gradient, the energy spread effect can be significantly mitigated, thus avoiding a drastic reduction in the FEL gain. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the output FEL radiation can become significant. To investigate this effect, we study the properties of the higher-order eigenmodes of a TGU-based, high-gain FEL, using both a simplified, analytically-solvable model and a variational technique. This formalism is then used to provide an estimate of the degree of transverse coherence for a representative soft X-ray, TGU FEL example.

TUP027

Initial Value Problem for an FEL Driven by an Asymmetric Electron Beam

FEL, radiation, undulator, simulation

433

P. Baxevanis, R.D. Ruth
SLAC, Menlo Park, California, USA

FEL configurations in which the driving electron beam is not axially symmetric (round) are important in the study of novel concepts (such as TGU-based FELs) but also become relevant when one wishes to explore the degree to which the deviation from symmetry-inevitable in practical cases-affects the performance of more conventional FEL schemes. In this paper, we present a technique for solving the initial value problem of such an asymmetric FEL. Extending an earlier treatment of ours, we start from a self-consistent, fully 3D, evolution equation for the complex amplitude of the electric field of the FEL radiation, which is then solved by expanding the radiation amplitude in terms of a set of orthogonal transverse modes. The numerical results from such an analysis are in good agreement with simulation and provide a full description of the radiation in the linear regime. Moreover, when the electron beam sizes are constant, this approach can be used to verify the predictions of the standard eigenmode formalism.

TUP028

Mode Contents Analysis of a Tapered Free Electron Laser

FEL, undulator, laser, simulation

437

S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S.D. Chen, C.-S. Hwang
NCTU, Hsinchu, Taiwan
C. Emma, C. Pellegrini
UCLA, Los Angeles, USA
K. Fang, S.-Y. Lee
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S. Serkez
DESY, Hamburg, Germany

For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP029

iSASE Study

FEL, radiation, undulator, simulation

442

K. Fang
Indiana University, Bloomington, Indiana, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
C. Emma, C. Pellegrini
UCLA, Los Angeles, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

TUP030

Mode Component Evolution and Coherence Analysis in Terawatt Tapered FEL

FEL, undulator, radiation, laser

446

K. Fang, S.D. Chen, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
C. Emma, C. Pellegrini
UCLA, Los Angeles, USA
K. Fang
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S. Serkez
DESY, Hamburg, Germany

A fast and robust algorithm is developed to decompose FEL radiation field transverse distribution into a set of orthonormal basis. Laguerre Gaussian and Hermite Gaussian can be used in the analysis. The information of mode components strength and Gaussian beam parameters allows users in downstream better utilize FEL. With this method, physics of mode components evolution from starting stage, to linear regime and post saturation are studied with detail. With these decomposed modes, correlation function can be computed with less complexity. Eigenmodes of the FEL system can be solved using this method.

TUP031

FEL Code Comparison for the Production of Harmonics via Harmonic Lasing

FEL, simulation, radiation, undulator

451

G. Marcus, W.M. Fawley
SLAC, Menlo Park, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Harmonic lasing offers an attractive option to significantly extend the photon energy range of FEL beamlines. Here, the fundamental FEL radiation is suppressed by various combinations of phase shifters, attenuators, and detuned undulators while the radiation at a desired harmonic is allowed to grow linearly. The support of numerical simulations is extensively used in evaluating the performance of this scheme. This paper compares the results of harmonic growth in the harmonic lasing scheme using three FEL codes: FAST, GENESIS, and GINGER.

TUP032

FEL Simulation and Performance Studies for LCLS-II

undulator, FEL, simulation, radiation

456

G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang, J. Wu
SLAC, Menlo Park, California, USA

The design and performance of the LCLS-II free-electron laser beamlines are presented using start-to-end numerical particle simulations. The particular beamline geometries were chosen to cover a large photon energy tuning range with x-ray pulse length and bandwidth flexibility. Results for self-amplified spontaneous emission and self-seeded operational modes are described in detail for both hard and soft x-ray beamlines in the baseline design.

TUP033

Broadly Tunable Free-Electron Laser for Four-wave Mixing Experiments with Soft X-ray Pulses

undulator, FEL, laser, simulation

461

G. Marcus
SLAC, Menlo Park, California, USA
G. Penn
LBNL, Berkeley, California, USA
A. Zholents
ANL, Argonne, Illinois, USA

This paper examines a FEL design for the production of three soft x-ray pulses from a single electron beam suitable for four-wave mixing experiments. Independent control of the wavelength, timing and angle of incidence of the three ultra-short, ultra-intense pulses with exquisite synchronization is critical. A process of selective amplification where a chirped electron beam and a tapered undulator are used to isolate the gain region to only a short fraction of the electron beam is explored in detail. Numerical particle simulations are used to demonstrate the essential features of this scheme in the context of the LCLS-II design study.

TUP036

Observation of Smith-Purcell Radiation at 32 GHz from a Multi-channel Grating with Sidewalls

radiation, experiment, simulation, free-electron-laser

470

J.T. Donohue
CENBG, Gradignan, France
J. Gardelle, P. Modin
CEA, LE BARP cedex, France

In a demonstration experiment at 5 GHz, we found copious emission of coherent Smith-Purcell (SP) radiation at the fundamental frequency of the evanescent surface wave, when the grating had sidewalls. Reaching higher frequencies requires a reduction in the size of the grating, which leads to a considerable reduction in power. To partially compensate this, we suggested superposing several copies of the reduced grating in parallel. A test of this concept has been performed with a seven-channel grating, at a frequency near 32 GHz. The SP radiation signals were observed directly with a fast oscilloscope. Power levels were of order 5 kW, in fair agreement with three-dimensional simulations made using the code "MAGIC".

TUP040

Flying RF Undulator

undulator, radiation, resonance, focusing

474

A.V. Savilov, I.V. Bandurkin, S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

A new concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the -1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton’s photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particles and the co-propagating rf pulse. This work is supported by the Russian Foundation for Basic Research (Projects 14-08-00803 and 14-02-00691).

Poster TUP040 [0.189 MB]

TUP042

High Efficiency Lasing with a Strongly Tapered Undulator

undulator, laser, radiation, experiment

478

J.P. Duris, P. Musumeci
UCLA, Los Angeles, California, USA

Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073 and University of California Office of the President award 09-LR-04-117055-MUSP.
Typical electrical to optical energy conversion efficiencies for FELs are limited by the Pierce parameter to 10^-3 or smaller. Undulator tapering schemes have enabled extraction of as much as 1 or 2% of the electron energy. Recently, the UCLA BNL helical inverse free electron laser (IFEL) experiment at ATF demonstrated energy doubling and acceleration of 30% of an electron beam from 52 to 93 MeV with a modest 10¹¹ W power CO2 laser pulse. By reversing and retuning the undulator, the electrons may be violently decelerated, thereby transferring energy from the beam to the laser pulse. Simulations show that by sending a 1 kA, 70 MeV electron beam and 100 GW laser into a prebuncher and the reversed undulator, 41% of the electron beam energy should be converted to radiation, allowing the laser pulse power to grow to 127 GW.

TUP045

IFEL Driven Micro-Electro-Mechanical System Free Electron Laser

undulator, FEL, laser, radiation

481

N.S. Sudar, J.P. Duris, P. Musumeci
UCLA, Los Angeles, USA

The Free Electron Laser has provided modern science with a tunable source of high frequency, high power, coherent radiation. To date, short wavelength FEL's have required large amounts of space in order to achieve the necessary beam energy to drive the FEL process and to reach saturation of the output radiation power. By utilizing new methods for beam acceleration as well as new undulator technology, we can decrease the space required to build these machines. In this paper, we investigate a scheme by which a tabletop XUV FEL might be realized. Utilizing the Rubicon Inverse Free Electron Laser (IFEL) at BNL together with micro-electro-mechanical system (MEMS) undulator technology being developed at UCLA, we propose a design for a compact XUV FEL.

TUP046

Terahertz FEL based on Photoinjector Beam in RF Undulator

undulator, focusing, FEL, radiation

485

S.V. Kuzikov, I.V. Bandurkin, M.E. Plotkin, A.V. Savilov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
A.V. Savilov
NNGU, Nizhny Novgorod, Russia

Photoinjectors, which can produce picosecond electron bunches of MeV-level, are attractive for THz generation. Fortunately, a long distance to reach scattering power saturation in FEL is not necessary, if bunch length is shorter than the produced THz half-wavelength. However, the energy of several MeVs does not allow providing long traveling of the flying bunch without longitudinal divergence. That is why, we suggest using specific RF undulator in a form of the normal wave in the helical waveguide at 3 cm wavelength. The mentioned wave has the -1st space harmonic with transverse fields and negative phase velocity (responsible for particle wiggling). This wave has also the 0th harmonic with longitudinal field and positive phase velocity equal to bunch velocity. Due to the synchronous 0th harmonic one can channel low-energy bunches (due to longitudinal focusing field) as far as several meters distance. One might also inject electron bunches in slightly accelerating field, in this case the output THz pulse obtain nearly linear frequency modulation. Such long THz pulses with the mentioned modulation of the frequency can be effectively compressed by pair of diffraction gratings.

Poster TUP046 [2.914 MB]

TUP047

Chirped Pulse Superradiant Free-electron Laser

radiation, undulator, laser, FEL

489

Y.-C. Huang, C.H. Chen
NTHU, Hsinchu, Taiwan
J. Wu, Z. Zhang
SLAC, Menlo Park, California, USA

Funding: This work is supported by Ministry of Science and Technology under Contract NSC 102-2112-M-007-002-MY3
When a short electron bunch traverses an undulator and radiates a wavelength significantly longer than the bunch length, the electrons quickly loses energy through so-called superradiance and generate a negatively chirped radiation frequency at the output. In this paper, we develop a theory to describe this chirped-pulse radiation and numerically demonstrate pulse compression by using a quadratic phase filter. As a design example at THz, a photoinjector/linac system generates a 15 MeV electron bunch containing 15-pC charge in a 60-fs duration. The electrons radiate a chirped pulse at 2.5 THz from a 1.5 m long undulator with a period of 5.6 cm and undulator parameter of 1.7. By using a grating pair, the output THz field can be compressed from 27 to 3 cycles. As another example at EUV, a future dielectric laser accelerator [1] is assumed to generate a 100 MeV electron bunch containing 75-fC charge in 1-nm long length. The electrons radiate a chirped EUV pulse at 13.5 nm from a 15.8 cm long dielectric laser undulator [2] with a period of 1.05 mm and undulator field of 3.3 T. By using a quadratic phase filter as a pulse compressor, the peak power of the EUV radiation is increased from 0.7 to 10 kW.
*Y.C. Huang and R.L. Byer, Appl. Phys. Lett. 69 (15), (1996) 2185-2177.
**T. Plettner, R. L. Byer., Phys. Rev. ST Accel. Beams 11, (2008) 030704.

TUP054

Status of Electron Beam Slicing Project at NSLS-II, BNL

radiation, storage-ring, photon, linac

496

A. He, F.J. Willeke, L.-H. Yu
BNL, Upton, Long Island, New York, USA

The Electron Beam Slicing (e-beam slicing) at NSLS-II, Brookhaven National Laboratory, supported by the Laboratory Directed Research and Development (LDRD) Program, is focused on the development of the new method to generate ultra-short x-ray pulses using focused short low energy (∼20 MeV) electron bunches to create short slices of electrons from the circulating electron bunches in a synchrotron radiation storage ring. The e-beam slicing activities are staged in 3 main phases. In Phases 0, the theory of e-beam slicing is developed, the low energy linac compressor is simulation designed, the radiation separation between the satellite and core is analyzed by simulation and the properties of the e-beam slicing system are discussed and compared with other ultra-short x- ray sources. Phase 0 has completed successfully, Phase 1 is under way. This paper presents an update on the status of Phase 0.

TUP057

Development of Compact THz-FEL System at Kyoto University

undulator, gun, FEL, simulation

501

S. Suphakul, T. Kii, H. Ohgaki, Y. Tsugamura, H. Zen
Kyoto University, Kyoto, Japan
Q.K. Jia
USTC/NSRL, Hefei, Anhui, People's Republic of China

We are developing a compact accelerator based terahertz (THz) radiation source by free-electron laser (FEL) at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6 cell BNL type photocathode RF-gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles and an undulator. The system generates an ultra-short electron pulse in a few hundred femtoseconds shorter than radiation wavelength, resulting in super-radiant emission from the undulator. The target radiation wavelength is 100 to 300 μm. A tracking simulation and optimization are performed by using PARMELA and General Particle Tracer (GPT) code. The FEL radiations are analyzed by a 1 dimensional FEL theory. The design parameters, simulation results and status are reported and discussed in this paper.

TUP060

Potential Photochemical Applications of the Free Electron Laser Irradiation Technique in Living Organisms

FEL, experiment, radiation, laser

505

F. Shishikura, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan
T. Sakae
Nihon University School of Dentistry at Matsudo, Matsudo-shi, Japan

In 2001, the Laboratory for Electron Beam Research and Application (LEBRA) achieved the first lasing of 0.9–6.5 microns near-infrared free electron lasers (FELs), in which higher harmonics were generated by using nonlinear optical crystals. Following this breakthrough, we have paid considerable attention to LEBRA-FEL’s potential for investigating photochemical reactions in living organisms. We have established a micro-irradiation technique using an optical fiber connected to a fine tapered glass rod of <5 microns in diameter, enabling FEL irradiation of a single cell and even the inner organelles of live cells. We then verified that visible LEBRA-FEL light can control the germination of lettuce seeds, a well-known photochemical reaction, and determined that red light (660 nm FEL) promotes germination and far-red light (740 nm FEL) inhibits it. Here, we summarize the efficiency of various visible wavelengths of LEBRA-FEL light, ranging from 0.4–0.8 microns, for regulating photoreactions in lettuce seeds and we also summarize the efficiency of infrared wavelengths up to 20 microns, which can be generated by combined use of the LEBRA-FEL and the Kyoto University FEL.
We thank the staff of Prof. T. Morii (Institute of Advanced Energy, Kyoto Univ.) for helpful assistance.

TUP064

Narrow Linewidth, Chirp-Control and Radiation Extraction Optimization in an Electrostatic Accelerator FEL Oscillator

FEL, laser, radiation, wiggler

509

H. S. Marks, A. Gover, H. Kleinman, J. Wolowelsky
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
D. Borodin, M. Einat, M. Kanter, Y. Lasser, Yu. Lurie
Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel

In recent years the electrostatic accelerator FEL based in Ariel has undergone many upgrades. By varying the accelerating potential the resonator allows lasing between 95-110 GHz. It is now possible to remotely control the output reflectivity of the resonator and thereby vary both the power built up in the resonator and that emitted. This has allowed fine control over the power for different user experiments. A voltage ramping device has been installed at the resonator/wiggler to correct drops in voltage which occur due to electrons striking the walls of the beam line. This has allowed stable pulses of just over 50 μs with a chirp rate of ~80 kHz/μs.

TUP066

Facility for Coherent THz and FIR Radiation

bunching, FEL, undulator, radiation

512

A. Meseck
HZB, Berlin, Germany
V.G. Ziemann
Uppsala University, Uppsala, Sweden

Linac based THz sources are increasingly becoming the method of choice for a variety of research fields, justifying the increasing demand for high repetition rate THz FEL facilities world wide. In particular, pump and probe experiments with THz and IR radiation are of major interest for the user community. In this paper, we propose a facility which accommodates an SRF-linac driven cw THz-FEL in combination with an IR undulator which utilizes the microbunched beam. The layout permits almost perfect synchronization between pump and probe pulse as well as nearly independently tunable THz and IR radiation.

Poster TUP066 [1.655 MB]

TUP070

Numerical Calculation of Diffraction Loss for Characterisation of a Partial Waveguide FEL Resonator

FEL, laser, simulation, radiation

521

Q. Fu, B. Qin, P. Tan, K. Xiong, Y.Q. Xiong
HUST, Wuhan, People's Republic of China

Waveguide is widely used in long wavelength Free-Electron Lasers to reduce diffraction losses. In this paper the amplitude and phase transverse distribution of light emission produced in a partial-waveguide FEL resonator is calculated by Fresnel principle. To acquire high power out-coupled and optimize resonator structure of HUST THz-FEL, the characterisation of reflecting mirror is discussed to reduce diffraction loss.

TUP072

Present Status of Coherent Electron Cooling Proof-of-principle Experiment

cavity, ion, gun, laser

524

I. Pinayev, Z. Altinbas, D.R. Beavis, S.A. Belomestnykh, I. Ben-Zvi, K.A. Brown, J.C. Brutus, A.J. Curcio, L. DeSanto, A. Elizarov, C. Folz, D.M. Gassner, H. Hahn, Y. Hao, C. Ho, Y. Huang, R.L. Hulsart, M. Ilardo, J.P. Jamilkowski, Y.C. Jing, F.X. Karl, D. Kayran, R. Kellermann, N. Laloudakis, R.F. Lambiase, V. Litvinenko, G.J. Mahler, M. Mapes, W. Meng, R.J. Michnoff, T.A. Miller, M.G. Minty, P. Orfin, A. Pendzick, F. Randazzo, T. Rao, J. Reich, T. Roser, J. Sandberg, B. Sheehy, J. Skaritka, K.S. Smith, L. Snydstrup, A.N. Steszyn, R. Than, C. Theisen, R.J. Todd, J.E. Tuozzolo, E. Wang, G. Wang, D. Weiss, M. Wilinski, T. Xin, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
G.I. Bell, J.R. Cary, K. Paul, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb
Tech-X, Boulder, Colorado, USA
C.H. Boulware, T.L. Grimm, R. Jecks, N. Miller
Niowave, Inc., Lansing, Michigan, USA
M.A. Kholopov, P. Vobly
BINP SB RAS, Novosibirsk, Russia
V. Litvinenko
Stony Brook University, Stony Brook, USA
P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work supported by Stony Brook University and by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The status of FEL-based Coherent Electron Cooling Proof-of-principle Experiment at BNL is presented. The experimental set-up is comprised of a 2 MeV CW SRF electron gun and 20 MeV CW SRF linac and 8-m long helical FEL amplifier. The status of the accelerator commissioning, and progress in the construction of the helical undulator at Budker INP, is also reported

TUP073

High Power Operation of the THz FEL at ISIR, Osaka University

FEL, operation, linac, gun

528

K. Kawase, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, G. Isoyama, R. Kato, K. Kubo, K. Miyazaki, S. Suemine, A. Tokuchi, R. Tsutsumi, M. Yaguchi
ISIR, Osaka, Japan

The THz FEL at Osaka University is based on the L-band linac that provides a multi-bunch electron beam with an 8 us duration in the energy range from 12.5 to 20 MeV. Although the RF frequency of the linac is 1.3 GHz, the bunch intervals are expanded to 9.2 ns for the FEL using a sub-harmonic buncher system that operates at 10⁸ MHz, to enhance the bunch charge to 1 nC/bunch. The FEL covers the wavelength range from 30 to 150 um, and maximum energies of the macropulse and the micropulse are 3.7 mJ and 11 uJ, respectively, at ~70 um measured at an experimental station. To enhance the FEL power further, the electron beam current cannot be increased simply because the beam loading in the acceleration tube is too high. To solve this problem, we have developed a 27 MHz grid pulser for the thermionic electron gun that makes the bunch intervals 4 times longer and increases charge of the bunch 4 times higher whereas the beam loading is the same as that in the 108 MHz mode. In this new operation mode, where a single FEL pulse lases in the cavity, we have succeeded in obtaining the micropulse energy exceeding 100 uJ at a wavelength of 68 um.

TUP077

Characteristics of Transported Terahertz-wave Coherent Synchrotron Radiation at LEBRA

FEL, radiation, synchrotron-radiation, synchrotron

541

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan

Funding: This work has been supported in part under the Visiting Researcher's Program of the Research Reactor Institute, Kyoto University, and ZE Research Program ZE25B-7, Kyoto University.
Nihon University and National Institute of Advanced Industrial Science and Technology have jointly developed terahertz-wave coherent synchrotron radiation (CSR) at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University since 2011. We have already observed intense terahertz-wave radiation from a bending magnet located above an undulator dedicated for an infrared free-electron laser (FEL), and confirmed it to be CSR [*]. Moreover, we have transported the CSR to an experimental room, which is next to the accelerator room across a shield wall, using an infrared FEL beamline. The transported CSR beam can be applied to two-dimensional imaging and spectroscopy experiments. In this presentation, characteristics of the CSR beam and applications for the CSR beam at LEBRA will be reported.
* N. Sei et al., “Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA”, J. Phys. D, 46 (2013) 045104.

TUP079

A Swedish Compact Linac-based THz/X-ray Source at FREIA

cavity, radiation, gun, linac

545

V.A. Goryashko
Private Address, Uppsala, Sweden
A. Opanasenko
NSC/KIPT, Kharkov, Ukraine
V. Zhaunerchyk
University of Gothenburg, Gothenburg, Sweden

THz radiation enables probing and controlling low-energy excitations in matter such as molecular rotations, DNA dynamics, spin waves and Cooper pairs. In view of growing interest to the THz radiation, the Swedish FEL Center and FREIA Laboratory are working on the conceptual design of a compact multicolor photon source for multidisciplinary research. We present the design of such a source driven by high-brightness electron bunches produced by a superconducting linear accelerator. A THz source is envisioned as an FEL oscillator since this enables not only generation of THz pulses with a bandwidth down to 0.01% (with inter-pulse locking technique) but also generation of short pulses with several cycles in duration by detuning the resonator. For pump-probe experiments, the THz source will be complemented with an X-ray source. One of the most promising options is the inverse Compton scattering of quantum laser pulses from electron bunches. Such an X-ray source will operate in water window with output intensity comparable to a second generation synchrotron. The envisioned THz/X-ray source is compact with a cost comparable to the cost of one beamline at a synchrotron.

TUP080

Towards an X-ray FEL at the MAX IV Laboratory

FEL, linac, gun, laser

549

S. Werin, F. Curbis, M. Eriksson, C. Quitmann, S. Thorin
MAX-lab, Lund, Sweden
P. Johnsson
Lund University, Lund, Sweden

The design of the 3 GeV linac for the MAX IV facility was done to provide the ability to host a future FEL in the hard X-ray as well as in the soft X-ray range. The linear accelerator, with its two bunch compressors, is now under commissioning. Through the years increasing details for the actual FEL have been discussed and presented. In parallel a steering group for the science case for a Swedish FEL has worked and engaged a large number of Swedish user groups. These two paths are now converging into a joint project to develop the concept of an FEL at MAX IV. We will report on the paths to FEL performance based on the 3 GeV injector, FEL design considerations, the scientific preparation of the project, the linac commissioning and the strategy and priorities.

TUP081

Configuration and Status of the Israeli THz Free Electron Laser

FEL, wiggler, laser, RF-structure

553

A. Friedman, N. Balal, V.L. Bratman, E. Dyunin, Yu. Lurie, E. Magori
Ariel University, Ariel, Israel
A. Gover
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel

Funding: This project is funded in part by Israel Ministry of Defense.
A THz FEL is being built in Ariel University. This project is a collaboration between Ariel University, and Tel Aviv University. Upon completion it is intended to become a user facility. The FEL is based on a compact photo cathode gun (60 cm) that will generate an electron beam at energies of 4.5 - 6.5 MeV. The pulses are planned to be of 300 pico Coulomb for a single pulse, and of up to 1.5 nano Coulomb for a train of pulses. The FEL is designed to emit radiation between 1 and 5 THz. It is planned to operate in the super radiance regime. The configuration of the entire system will be presented, as well as theoretical and numerical results for the anticipated output of the FEL, which is in excess of 150 KW instantaneous power. The bunching of the electron bean will be achieved by mixing two laser beams on the photo-cathode. The compression of the beam will be achieved be introducing an energy chierp to the beam and passing it through a helical chicane. We plan on compressing the single pulse to less than 150 femto seconds. The status of the project at the time of the conference will be presented.

Poster TUP081 [3.276 MB]

TUP082

Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation

laser, radiation, undulator, experiment

556

A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

TUP083

ALPHA – The THz Radiation Source based on AREAL

radiation, undulator, FEL, emittance

561

T.L. Vardanyan, G.A. Amatuni, V.S. Avagyan, A. Grigoryan, B. Grigoryan, M. Ivanyan, V.G. Khachatryan, V.H. Petrosyan, V. Sahakyan, A. Sargsyan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan, G.S. Zanyan
CANDLE SRI, Yerevan, Armenia

Advanced Research Electron Accelerator Laboratory (AREAL) based on photo cathode RF gun is under construction at the CANDLE. The basic aim of this new facility is to generate sub-picosecond duration electron bunches with an extremely small beam emittance and energies up to 50 MeV. One of the promising directions of the facility development is the creation of ALPHA (Amplified Light Pulse for High-end Applications) experimental stations with coherent radiation source in THz region based on the concept of both conventional undulator and novel radiation sources. The status of the AREAL facility, the main features and outlooks for the ALPHA station are presented in this work.

TUP085

FERMI Status Report

FEL, experiment, laser, operation

564

M. Svandrlik, E. Allaria, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, L. Fröhlich, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, C. Spezzani, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI, the seeded FEL located at the Elettra laboratory in Trieste, Italy, is now in regular operation for users with its first FEL line, FEL-1, which covers the wavelength range between 100 and 20 nm. We will give an overview of the typical operating modes of the facility for users and we will report on the status of beamlines and experimental stations. Three beamlines are now opened for users, three more are in construction. Meanwhile, the second FEL line of FERMI, FEL-2, a HGHG double stage cascade covering the wavelength range 20 to 4 nm is still under commissioning; we will report on the latest results in particular at the shortest wavelength, 4 nm in the fundamental.

TUP086

Experiment Preparation Towards a Demonstration of Laser Plasma Based Free Electron Laser Amplification

laser, undulator, FEL, free-electron-laser

569

M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Cassinari, L. Chapuis, M.E. El Ajjouri, C. Herbeaux, N. Hubert, M. Labat, A. Lestrade, A. Loulergue, J. Lüning, O. Marcouillé, J.L. Marlats, F. Marteau, C. Miron, P. Morin, F. Polack, K. Tavakoli, M. Valléau, D. Zerbib
SOLEIL, Gif-sur-Yvette, France
I.A. Andriyash, G. Lambert, V. Malka, C. Thaury
LOA, Palaiseau, France
S. Bielawski, C. Evain, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
X. Davoine
CEA/DAM/DIF, Arpajon, France

One direction towards compact Free Electron Laser is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence. Applying seeding techniques also enables to reduce the required undulator length. Rapidly developing Laser Wakefield Accelerators (LWFA) are already able to generate synchrotron radiation. With the presently achieved electron divergence and energy spread an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract in the more general context of LUNEX5. Electron beam transport follows different steps with strong focusing thanks to variable strength permanent magnet quadrupoles, demixing chicane with conventional dipoles, and a second set of quadrupoles for further focusing in the undulator. Progress on the equipment preparation and expected performance are described.

TUP087

The Status of LUNEX5 Project

FEL, laser, undulator, operation

574

M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Cassinari, L. Chapuis, J. Daillant, M. Diop, M.E. El Ajjouri, C. Herbeaux, N. Hubert, M. Labat, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, C. Miron, P. Morin, A. Nadji, F. Polack, F. Ribeiro, J.P. Ricaud, P. Roy, K. Tavakoli, M. Valléau, D. Zerbib
SOLEIL, Gif-sur-Yvette, France
S. Bielawski
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
B. Carré, D. Garzella
CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
X. Davoine
CEA/DAM/DIF, Arpajon, France
N. Delerue
LAL, Orsay, France
G. Devanz, A. Mosnier
CEA/DSM/IRFU, France
A. Dubois, J. Lüning
CCPMR, Paris, France
C. Evain, E. Roussel, C. Szwaj
PhLAM/CERLA, Villeneuve d'Ascq, France
G. Lambert, R. Lehé, V. Malka, A. Rousse, C. Thaury
LOA, Palaiseau, France
C. Madec
CEA/IRFU, Gif-sur-Yvette, France

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, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling seeding with High order Harmonic in Gas and echo configurations and pilot user applications. Concerning the superconducting linac, the electron beam dynamics has been modified from a scheme using a third harmonic linearizer and a compression chicane to dog-leg coupled to sextupoles. Besides, the choice of the gun is under revision for fulfilling to 10 kHz repetition rate. Following transport theoretical studies of longitudinal and transverse manipulation of a LWFA electron beam enabling to provide theoretical amplification, a test experiment is under preparation in collaboration with the Laboratoire d’Optique Appliquée towards an experimental demonstration.

TUP088

Free Electron Lasers in 2014

FEL, undulator, laser, free-electron-laser

580

J. Blau, K. R. Cohn, W.B. Colson, W.W. Tomlinson
NPS, Monterey, California, USA

Funding: This work has been supported by the Office of Naval Research and the High Energy Laser Joint Technology Office.
Thirty-eight 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.

TUP089

The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) Project

undulator, FEL, radiation, linac

585

A.A. Aksoy, Ö. Karslı, C. Kaya, O. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
P. Arıkan
Gazi University, Faculty of Arts and Sciences, Teknikokullar, Ankara, Turkey
S. Özkorucuklu
Istanbul University, Istanbul, Turkey

Funding: Work is supported by Ministry of Development of Turkey with Grand No: DPT2006K-120470
The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) which is proposed as a first facility of Turkish Accelerator Center (TAC) Project will operate two Infra-Red Free Electron Lasers (IR-FEL) covering the range of 3-250 microns. The facility will consist of an injector fed by a thermionic triode gun with two-stage RF bunch compression, two superconducting accelerating modules operating at continuous wave (CW) mode and two independent optical resonator systems with different undulator period lengths. The electron beam will also be used to generate Bremsstrahlung radiation. The facility aims to be first user laboratory in the region of Turkey in which both electromagnetic radiation and particles will be used. In this paper, we discuss design goals of the project and present status and road map of the project.

TUP093

A Beam Test of Corrugated Structure for Passive Linearizer

simulation, quadrupole, linac, controls

593

H.-S. Kang, J.H. Hong
PAL, Pohang, Kyungbuk, Republic of Korea

A dechirper which is a vacuum chamber of two corrugated, metallic plates with adjustable gap was successfully tested at Pohang, in August 2013. Another beam test was carried out to test the same structure to see if the corrugated plates may work as a linearizer. The test result will be presented together with the simulation result.

TUP095

Design of a Compact Light Source Accelerator Facility at IUAC, Delhi

gun, radiation, undulator, laser

596

S. Ghosh, R.K. Bhandari, G.K. Chaudhari, D. Kanjilal, J. Karmakar, N. Kumar, A. Pandey, P. Patra, A. Rai, B.K. Sahu
IUAC, New Delhi, India
A.S. Aryshev, J. Urakawa
KEK, Ibaraki, Japan
A. Deshpande, T.S. Dixit
SAMEER, Mumbai, India
V. Naik, A. Roy
VECC, Kolkata, India

Funding: * The project is supported jointly by Board of Research in Nuclear Sciences and Inter University Accelerator Center
The demand for a light source with high brightness and short pulse length from the researchers in the field of physical, chemical, biological and medical sciences is growing in India. To cater to the experimental needs of multidisciplinary sciences, a project to develop a compact Light Source at Inter University Accelerator Centre (IUAC) has been taken up. In the first phase of the project, prebunched [1] electron beam of ~ 8 MeV will be produced by a photocathode RF gun and coherent THz radiation will be produced by a short undulator magnet. In the second phase, the energy of the electron beam will be increased up to 50 MeV by two sets of superconducting niobium resonators. The coherent IR radiation will be produced by using an undulator magnet (conventional method) and X-rays by Inverse Compton Scattering. To increase the average brightness of the electromagnetic radiation, fabrication of superconducting RF gun is going to be started in a parallel development. In this paper the detailed design of the LSI accelerator complex as well as construction timetable will be presented. The physical principles of THz generation and major accelerator subsystems will be discussed.
[1] S. Liu & J.Urakawa, Proc. of FEL 2011, page-92

TUP097

Fast, Multi-band Photon Detectors based on Quantum Well Devices for Beam-monitoring in New Generation Light Sources

detector, laser, photon, monitoring

600

T. Ganbold
University of Trieste, School of Nanotechnology, Trieste, Italy
M. Antonelli, G. Cautero, R. Cucini, D.M. Eichert, W.H. Jark, R.H. Menk
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. Biasiol
IOM-CNR, Trieste, Italy

In order to monitor the photon-beam position for both diagnostics and calibration purposes, we have investigated the possibility to use InGaAs/InAlAs Quantum Well (QW) devices as position-sensitive photon detectors for Free-Electron Laser (FEL) or Synchrotron Radiation (SR). Owing to their direct, low-energy band gap and high electron mobility, such QW devices may be used also at Room Temperature (RT) as fast multi-band sensors for photons ranging from visible light to hard X-rays. Moreover, internal charge-amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. Segmented QW sensors have been preliminary tested with 100-fs-wide UV laser pulses and X-ray SR. The reported results indicate that these devices respond with 100-ps rise-times to ultra-fast UV laser pulses. Besides, X-ray tests have shown that these detectors are sensitive to beam position and exhibit a good efficiency in the collection of photo-generated carriers.

TUC01

Hard X-ray Self-Seeding Setup and Results at SACLA

undulator, FEL, radiation, photon

603

T. Inagaki, N. Adumi, T. Hara, T. Ishikawa, R. Kinjo, H. Maesaka, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
S. Goto, Y. Inubushi, T.K. Kameshima, T. Ohata, K. Tono
JASRI/SPring-8, Hyogo, Japan
T. Hasegawa, S. Tanaka
SES, Hyogo-pref., Japan
H. Kimura, A. Miura, H. Ohashi, H. Yamazaki
Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), Hyogo, Japan

In order to improve the spectral and temporal properties of XFEL, the self-seeding option based on the transmission crystal optics has been implemented in SACLA since 2012. The self-seeding setup composed of four dipole magnets that can generate up to 50 fs temporal delay and a diamond single crystal with the thickness of 180 micro-m has been installed at the position of the 9th undulator segment, which has been moved downstream. In 2013, the installation of all the components has been completed in August and the commissioning has been started in October. After a number of tuning processes such as the beam collimation and undulator K-value optimization, significant spectral narrowing has been confirmed at 10 keV with the C(400) Bragg reflection. The spectral bandwidth of seeded FEL is about 3 eV, which is nearly one order narrower than that of SASE measured without the diamond crystal. The peak spectral intensity of seeded FEL is about 5 times higher than that of SASE. Systematic optimization on beam properties is now in progress towards experimental use of seeded XFELs. This talk gives the overview of the plan, achieved results and ongoing R&D.

Slides TUC01 [20.337 MB]

TUC03

Generation of Optical Orbital Angular Momentum Using a Seeded Free Electron Laser

laser, FEL, radiation, free-electron-laser

609

P. Rebernik Ribič, G. De Ninno, D. Gauthier
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Funding: The research was in part funded by the TALENTS UP Programme (7th R&D Framework Programme, Specific Programme: PEOPLE - Marie Curie Actions - COFUND).
We propose an effective scheme for the generation of intense extreme-ultraviolet light beams carrying orbital angular momentum (OAM). The light is produced by a high-gain harmonic-generation free-electron laser (HGHG FEL), seeded using a laser pulse with a transverse staircase-like phase pattern. The transverse phase modulation in the seed laser is obtained by putting a phase-mask in front of the focusing lens, before the modulator. The staircase-like phase pattern is effectively transferred onto the electron beam in the modulator and the microbunching structure is preserved after frequency up-conversion in the radiator. During light amplification in the radiator, diffraction and mode selection drive the radiation profile towards a dominant OAM mode at saturation. With a seed laser at 260 nm, gigawatt power levels are obtained at wavelengths approaching those of soft x-rays. Compared to other proposed schemes to generate OAM with FELs, our approach is robust, easier to implement, and can be integrated into already existing FEL facilities without extensive modifications of the machine layout.

WEA04

First Lasing from a High Power Cylindrical Grating Smith-Purcell Device

radiation, simulation, experiment, cathode

611

H. Bluem, R.H. Jackson, J.D. Jarvis, A.M.M. Todd
AES, Medford, New York, USA
J.T. Donohue
CENBG, Gradignan, France
J. Gardelle, P. Modin
CEA, LE BARP cedex, France

Funding: Work supported by ONR under Contract No. N00014-10-C-0191 and N62909-13-1-N62.
Many applications of THz radiation remain impractical or impossible due to an absence of compact sources with sufficient power. A source where the interaction occurs between an annular electron beam and a cylindrical grating is capable of generating high THz power in a very compact package. The strong beam bunching generates significant power at the fundamental frequency and harmonics. A collaboration between Advanced Energy Systems and CEA/CESTA has been ongoing in performing proof-of-principle tests on cylindrical grating configurations producing millimeter wave radiation. First lasing was achieved in such a device. Further experiments performed with a 6 mm period grating produced fundamental power at 15 GHz, second harmonic power at 30 GHz and although not measured, simulations show meaningful third harmonic power at 45 GHz. Comparison with simulations shows very good agreement and high conversion efficiency. Planned experiments will increase the frequency of operation to 100 GHz and beyond. Ongoing simulations indicate excellent performance for a device operating at a fundamental frequency of 220 GHz with realistic beam parameters at 10 kV and simple extraction of the mode.

Slides WEA04 [2.344 MB]

WEB02

Beam Operation of the PAL-XFEL Injector Test Facility

gun, laser, emittance, cavity

615

J.H. Han, S.Y. Baek, M.S. Chae, H. J. Choi, T. Ha, J.H. Hong, J. Hu, W.H. Hwang, S.H. Jung, H.-S. Kang, C. Kim, C.H. Kim, I.Y. Kim, J.M. Kim, S.H. Kim, I.S. Ko, H.-S. Lee, J. Lee, S.J. Lee, W.W. Lee, C.-K. Min, G. Mun, D.H. Na, S.S. Park, S.J. Park, Y.J. Park, Y.G. Son, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

The Pohang Accelerator Laboratory X-ray Free electron Laser (PAL-XFEL) project was launched in 2011. This project aims at the generation of X-ray FEL radiation in a range of 0.1 to 10 nm for photon users with a bunch repetition rate of 60 Hz. The machine consists of a 10 GeV normal conducting S-band linear accelerator and five undulator beamlines. The linac and two undulator beamlines will be constructed by the end of 2015 and first FEL radiation is expected in 2016. As a part of preparation for the project, an Injector Test Facility was constructed in 2012. Since December 2012, beam commissioning is being carried out to find optimum operating conditions and to test accelerator components including RF, laser, diagnostics, magnet, vacuum and control. We present the status of beam commissioning and components tests at the test facility.

Slides WEB02 [10.249 MB]

WEB03

European XFEL Construction Status

photon, undulator, laser, diagnostics

623

W. Decking
DESY, Hamburg, Germany
F. Le Pimpec
XFEL. EU, Hamburg, Germany

The European XFEL is presently constructed in the Hamburg region, Germany. It aims at producing X-rays in the range from 260 eV up to 24 keV out of three undulators that can be operated simultaneously with up to 27000 pulses/second. The FEL is driven by a 17.5 GeV linear accelerator based on TESLA-type superconducting accelerator modules. This paper presents the status of major components, the present project schedule and a summary of beam parameters that are adapted to the evolving needs of the users.

Slides WEB03 [12.982 MB]

WEB04

The New IR FEL Facility at the Fritz-Haber-Institut in Berlin

FEL, cavity, radiation, undulator

629

W. Schöllkopf, W. Erlebach, S. Gewinner, H. Junkes, A. Liedke, G. Meijer, A. Paarmann, G. von Helden
FHI, Berlin, Germany
H. Bluem, D. Dowell, R. Lange, J. Rathke, A.M.M. Todd, L.M. Young
AES, Princeton, New Jersey, USA
S.C. Gottschalk
STI, Washington, USA
U. Lehnert, P. Michel, W. Seidel, R. Wünsch
HZDR, Dresden, Germany

A mid-infrared oscillator FEL has been commissioned at the Fritz-Haber-Institut. The accelerator consists of a thermionic gridded gun, a subharmonic buncher and two S-band standing-wave copper structures [1,2]. It provides a final electron energy adjustable from 15 to 50 MeV, low longitudinal (<50 keV-ps) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micro-pulse repetition rate of 1 GHz and a macro-pulse length of up to 15 μs. Regular user operation started in Nov. 2013 with 6 user stations. Pulsed radiation with up to 100 mJ macro-pulse energy at about 0.5% FWHM bandwidth is routinely produced in the wavelength range from 4 to 48 μm. We will describe the FEL design and its performance as determined by IR power, bandwidth, and micro-pulse length measurements. Further, an overview of the new FHI FEL facility and first user results will be given. The latter include, for instance, spectroscopy of bio-molecules (peptides and small proteins) conformer selected or embedded in superfluid helium nano-droplets at 0.4 K, as well as vibrational spectroscopy of mass-selected metal-oxide clusters and protonated water clusters in the gas phase.
[1] W. Schöllkopf et al., MOOB01, Proc. FEL 2012.
[2] W. Schöllkopf et al., WEPSO62, Proc. FEL 2013.

Slides WEB04 [12.785 MB]

WEB05

FLASH: First Soft X-ray FEL Operating Two Undulator Beamlines Simultaneously

operation, laser, undulator, photon

635

K. Honkavaara, B. Faatz, J. Feldhaus, S. Schreiber, R. Treusch, M. Vogt
DESY, Hamburg, Germany

FLASH, the free electron laser user facility at DESY (Hamburg, Germany), has been upgraded with a second undulator beamline FLASH2. After a shutdown to connect FLASH2 to the FLASH linac, FLASH1 is back in user operation since February 2014. Installation of the FLASH2 electron beamline has been completed early 2014, and the first electron beam was transported into the new beamline in March 2014. The commissioning of FLASH2 takes place in 2014 parallel to FLASH1 user operation. This paper reports the status of the FLASH facility, and the first experience of operating two FEL beamlines.

Slides WEB05 [2.481 MB]

THA01

THz Streak Camera for FELTemporal Diagnostics: Concepts and Considerations

FEL, laser, photon, free-electron-laser

640

P.N. Juranic, R. Abela, I. Gorgisyan, C.P. Hauri, R. Ischebeck, B. Monoszlai, L. Patthey, C. Pradervand, M. Radovic, L. Rivkin, V. Schlott, A.G. Stepanov
PSI, Villigen PSI, Switzerland
I. Gorgisyan, C.P. Hauri, L. Rivkin
EPFL, Lausanne, Switzerland
R. Ivanov, P. Peier
DESY, Hamburg, Germany
J. Liu
XFEL. EU, Hamburg, Germany
B. Monoszlai
University of Pecs, Pécs, Hungary
K. Ogawa, T. Togashi, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
S. Owada
JASRI/RIKEN, Hyogo, Japan

The accurate, non-destructive measurements of FEL pulse length and arrival time relative to an experimental laser are necessary for operators and users alike. The FEL operators can get a better understanding of their machine and the optics of an FEL by examining the pulse length changes of the photons coming to the user stations, and the users can use the arrival time and pulse length information to better understand their data. PSI has created the pulse arrival and length monitor (PALM) based on the THz-streak camera concept for measurement at x-ray FELs, meant to be used at the upcoming SwissFEL facility. The first results from the experimental beamtime at SACLA will be presented, showcasing the accuracy and reliability of the device. Further plans for improvement and eventual integration into SwissFEL will also be presented.

Slides THA01 [5.798 MB]

THA03

A Plan for the Development of Superconducting Undulator Prototypes for LCLS-II and Future FELs

undulator, FEL, linac, vacuum

649

P. Emma, N.R. Holtkamp, H.-D. Nuhn
SLAC, Menlo Park, California, USA
D. Arbelaez, J.N. Corlett, S.A. Myers, S. Prestemon, D. Schlueter
LBNL, Berkeley, California, USA
C.L. Doose, J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, M. Kasa, G. Pile, E. Trakhtenberg
ANL, Argonne, Ilinois, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515, DE-AC02-05CH11231, and DE-AC02-06CH11357.
Undulators serve as the primary source of radiation for modern storage rings, and more recently for the advent of Free-Electron Lasers (FELs). The performance of future FELs can be greatly enhanced using the much higher magnetic fields of superconducting undulators (SCU). For example, the LCLS-II hard x-ray undulator can be shortened by up to 70 m using an SCU in place of a PMU (permanent magnet undulator), or its spectral performance can be critically improved when using a similar length. In addition, SCUs are expected to be orders of magnitude less sensitive to radiation dose; a major issue at LCLS-II with its 1-MHz electron bunch rate. We present a funded R&D collaboration between SLAC, ANL, and LBNL, which aims to demonstrate the viability of superconducting undulators for FELs by building, testing, measuring, and tuning two 1.5-m long planar SCU prototypes using two different technologies: NbTi at ANL and Nb3Sn at LBNL. Our goal is to review and reassess the LCLS-II HXR baseline plans (PMU) in July of 2015, after the development and evaluation of both prototypes, possibly in favor of an SCU for LCLS-II.

Slides THA03 [29.468 MB]

THB01

Simultaneous Measurement of Electron and Photon Pulse Duration at FLASH

photon, laser, free-electron-laser, FEL

654

S. Düsterer
DESY, Hamburg, Germany

One of the most challenging tasks for extreme ultraviolet, soft and hard X-ray free-electron laser photon diagnostics is the precise determination of the photon pulse duration, which is typically in the sub 100 fs range. In a larger campaign nine different methods, which are able to determine such ultrashort photon pulse durations were compared at FLASH. Radiation pulses at a wavelength of 13.5 nm and 24.0 nm together with the corresponding electron bunch duration were measured by indirect methods like analyzing spectral correlations, statistical fluctuations and energy modulations of the electron bunch, and also direct methods like autocorrelation techniques, THz streaking or reflectivity changes of solid state samples.

Slides THB01 [4.520 MB]

THB02

Experimental Results of Diagnostics Response for Longitudinal Phase Space

diagnostics, laser, radiation, free-electron-laser

657

F. Frei, V.R. Arsov, H. Brands, R. Ischebeck, B. Kalantari, R. Kalt, B. Keil, W. Koprek, F. Löhl, G.L. Orlandi, A. Saá Hernández, T. Schilcher, V. Schlott
PSI, Villigen PSI, Switzerland

At SwissFEL, electron bunches will be accelerated, shaped, and longitudinally compressed by different radio frequency (RF) structures (S-, C-, and X-band) in combination with magnetic chicanes. In order to meet the envisaged performance, it is planned to regulate the different RF parameters based on the signals from numerous electron beam diagnostics. Here we will present experimental results of the diagnostics response on RF phase and field amplitude variations that were obtained at the SwissFEL Injector Test Facility.

Slides THB02 [6.110 MB]

THP006

Optimization of the PITZ Photo Injector Towards the Best Achievable Beam Quality

laser, emittance, cathode, flattop

685

M. Khojoyan, M. Krasilnikov, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany

Funding: The work is supported by the German Federal Ministry of education and Research, project 05K10CHE and RFBR grant 13-02-91323.
Uniform 3D ellipsoids are proven to be the best distributions for high brightness charged particle beam applications due to the linear dependence of the space charge fields on the position within the distribution. Such electron bunches have lower emittance and are less sensitive to the machine settings and, therefore, should allow more reliable operation, which is one of the key requirements for single-pass free-electron lasers (FELs). The Photo Injector test facility at DESY, Zeuthen site (PITZ) is optimizing high brightness electron sources for linac based FELs such as the European XFEL. Recent measurements at PITZ using a photocathode laser with a flat-top temporal profile have revealed record low transverse emittance values at different bunch charges. As a next step towards the further improvement of the high quality beams, a cathode laser system, capable of producing quasi-3D ellipsoidal bunches is intended to be used at PITZ. In this work the beam dynamics optimization results for various bunch charges and for flat-top and 3D ellipsoidal cathode laser shapes are presented. For each working point the relative emittance growth is estimated due to possible deviations of the machine parameters.

THP007

Recent Electron Beam Optimization at PITZ

emittance, laser, gun, cathode

689

G. Vashchenko, P. Boonpornprasert, J.D. Good, M. Groß, I.I. Isaev, D.K. Kalantaryan, M. Khojoyan, G. Kourkafas, M. Krasilnikov, D. Malyutin, D. Melkumyan, A. Oppelt, M. Otevřel, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
G. Pathak
Uni HH, Hamburg, Germany
D. Richter
HZB, Berlin, Germany

High brightness electron sources for linac based freee-lectron lasers operating at short wavelength such as FLASH and the European XFEL are characterized and optimized at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). In the last few years PITZ mainly was used to condition RF guns for their later operation at FLASH and the European XFEL. Only limited time could be spent for beam characterization. However, recently we have performed emittance measurements and optimization for a reduced gun accelerating gradient which is similar to the usual operation conditions at FLASH. The results of these measurements are presented in this paper.

THP008

Evolution of a Warm Bunched Electron Beam in a Free Drift Region

plasma, space-charge, FEL, bunching

692

B. Maly, A. Friedman
Ariel University, Ariel, Israel

The state of the art of FELs development at present is "Table-Top X Ray Free Electron Lasers". Almost any such scheme involves a pre-bunched electron beam. In this paper we will analyze the evolution and "survivability" of bunching introduced into the beam in the free drift region prior to the wiggler. We examined analytically the first order degradation in beam bunching due to space charge effect. It will be shown that there is a limited interaction region, characterized by an exponential decay of the bunching factor, having a length inversely proportional to the square of the electron beam normalized temperature, followed by a stable bunch region. We will present examples of the effect for several schemes of X Ray and Tera Hertz FELs considered or being constructed presently.

THP010

Analysis of Beam Stability in the KAERI Ultrashort Pulse Accelerator

timing, kicker, septum, linac

697

H.W. Kim, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, Y. Kim, K. Lee, S.V. Miginsky, J. Mun, S. H. Park, S. Park, N. Vinokurov
KAERI, Daejon, Republic of Korea
K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, S.V. Miginsky, S. H. Park, N. Vinokurov
UST, Daejeon City, Republic of Korea
S.V. Miginsky, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

An RF-photogun-based linear accelerator for the Korea Atomic Energy Research Institute (KAERI) ultrashort pulse facility is under construction. It has a symmetry structure with four different beamlines. The UED beamlines will generate ultrashort electron pulses with over 10⁶ electrons per pulse for the single-shot measurements on femtoseconds dynamics of atomic or molecular structures. Electron bunches with an energy of ~3 MeV from the RF photogun can be compressed up to less than 50 fs by achromatic and isochronous bends. The intrinsic r.m.s. timing jitter of the pulses through the bends is estimated to be less than 30 fs with the r.m.s. energy fluctuation of 0.1%. In the THz pump and X-ray probe beamline, two successive laser pulses with a time interval of ~10 ns are used to generate two electron bunches having bunch charges more than 100 pC. Two electron bunches are accelerated by a linac up to ~25 MeV and separated into individual beamlines by a fast kicker. We will present on estimated timing jitter and effects of magnet errors to the beam dynamics in the accelerator by considering beam dilution effects.

THP011

Beam Measurement of Photocathode RF-gun for PAL-XFEL

laser, emittance, gun, solenoid

699

J.H. Hong, M.S. Chae, J.H. Han, H.-S. Kang, C.-K. Min, S.J. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea

The Injector Test Facility (ITF) at Pohang Accelerator Laboratory (PAL) was constructed to develop an injector for the PAL X-ray free-electron laser (PAL-XFEL) project. The PAL-XFEL design requires the injector to produce an electron beam with a slice emittance of 0.4 mm-mrad at the charge of 200 pC. A 4-hole type RF-gun has been successfully fabricated and tested at ITF. In this paper we report the recent beam-measurement results using the RF-gun at ITF. Emittance measurements have been carried out by changing laser and RF parameters.

THP013

Slice Emittance Measurement using RF Deflecting Cavity at PAL-XFEL ITF

emittance, quadrupole, cavity, gun

707

J. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, J.H. Hong, I.S. Ko, S.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

One of key characteristic for operating PAL-XFEL is the time-dependent transverse properties of a bunch, slice emittance. To achieve the design FEL performance of PAL-XFEL a slice emittance of 0.4 mm mrad at 0.2 nC is required. An Injector Test Facility (ITF) was constructed to study beam properties. In addition to projected emittance measurement, slice emittance measurement is being done using a transverse RF deflecting cavity. We presents results of slice emittance measurement at ITF and future plan for the optimization of operating condition.

THP014

Cyclotron-Undulator Cooling of a Free-Electron-Laser Beam

undulator, radiation, cyclotron, FEL

710

A.V. Savilov, I.V. Bandurkin, S.V. Kuzikov
IAP/RAS, Nizhny Novgorod, Russia

We propose methods of fast cooling of an electron beam, based on wiggling of particles in an undulator in presence of an axial magnetic field. We use a strong dependence of the axial electron velocity on the oscillatory velocity, when the electron cyclotron frequency is close to the frequency of electron wiggling in the undulator field. Such cooling may open a way for creating a compact X-ray free-electron laser based on the stimulated scattering of a powerful laser pulse on a moderately-relativistic (several MeV) electron beam. This work is supported by the Russian Foundation for Basic Research (Projects 14-08-00803 and 14-02-00691).

Poster THP014 [0.166 MB]

THP016

Optimization of FEL Performanceby Dispersion-based Beam-tilt Correction

FEL, simulation, lattice, radiation

714

M.W. Guetg, S. Reiche
PSI, Villigen PSI, Switzerland

In Free Electron Lasers (FEL) the beam quality is of crucial importance for the radiation power. A transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch. This leads to a reduced bunching and decreased FEL performance. The dominant sources of slice misalignments in FELs are the coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression, which is required for one of the key operation modes for the SwissFEL under construction at the Paul Scherrer Institute in Switzerland. The slice centroid shift can be corrected using multi-pole magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane.

THP018

The Seed Laser System for the Proposed VUV FEL Facility at NSRRC

laser, FEL, radiation, undulator

718

M.C. Chou, N.Y. Huang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan

The possibility of establishing a free electron laser facility in Taiwan has been a continuing effort at NSRRC in the past several years. The baseline design of the envisioned NSRRC FEL is a high gain harmonic generation (HGHG) FEL seeded by a 266 nm laser. The seed laser is produced by adding an optical parametric amplification (OPA) system pumped by upgrading the existing IR laser system. To provide broad tunability of the FEL radiation, the seed laser will be tunable. The spectrum considered for seeding the FEL is between 266 - 800 nm with peak power of 200 MW. The spatial and temporal overlap between the sub-100 fs electron bunch and the 100 fs UV seed laser is under study.

Poster THP018 [0.152 MB]

THP019

Higher-Order Moment Models of Longitudinal Pulse Shape Evolution in Photoinjectors

space-charge, wakefield, FEL, cavity

722

C.E. Mitchell, D. Filippetto, R. Huang, C. F. Papadopoulos, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA

The presence of longitudinal asymmetry, sometimes in the form of a one-sided tail, in the current profile emerging from low-energy photoinjectors can strongly impact the beam quality downstream of the compression system of the FEL beam delivery system. To understand the origin of this feature, an approximate model for the evolution of higher-order beam moments is developed in the presence of nonlinear kinematic effects and longitudinal space-charge. This model is applied to investigate the evolution of beam skewness for injector systems with parameters similar to the APEX Injector under investigation at Lawrence Berkeley National Laboratory.

THP020

Electron Beam Dynamics Optimization Using A Unified Differential Evolution Algorithm

emittance, controls, cavity, solenoid

726

J. Qiang, C.E. Mitchell
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
Accelerator beam dynamics design depends heavily on the use of control parameter optimization to achieve the best performance. In this paper, we report on electron beam dynamics optimization of a model photoinjector using a new unified differential evolution algorithm. We present the new unified differential evolution algorithm and benchmark its performance using several test examples. We also discuss the application of the algorithm in the multi-objective optimization of the photoinjector.

THP022

Theoretical Investigation of Coherent Synchrotron Radiation Induced Microbunching Instability in Transport and Recirculation Arcs

lattice, emittance, recirculation, damping

730

C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as recirculation or transport arcs, may lead to the microbunching instability. We extend and develop a semi-analytical approach of the CSR-induced microbunching instability for a general lattice, based on the previous formulation with 1-D CSR model [Phys. Rev. ST Accel. Beams 5, 064401 (2002)] and apply it to investigate the physical processes of microbunching amplification for two example transport arc lattices. We find that the microbunching instability in transport arcs has a distinguishing feature of multistage amplification (e.g, up to 6th stage for our example arcs in contrast to two stage amplification for a 3-dipole chicane). By further extending the concept of stage gain as proposed by Huang and Kim [Phys. Rev. ST Accel. Beams 5, 074401 (2002)], we developed a method to quantitatively characterize the microbunching amplification in terms of iterative or staged orders that allows the comparison of optics impacts on microbunching gain for different lattices. The parametric dependencies and Landau damping for our example lattices are also studied. Excellent agreement of the gain functions and spectra from Vlasov analysis with results from ELEGANT is achieved which helps to validate our analyses.

Poster THP022 [1.316 MB]

THP023

Simulation of Alpha Magnet Elements in Dipole-only Tracking Codes

dipole, simulation, beam-transport, coupling

735

J.W. Lewellen, F.L. Krawczyk
LANL, Los Alamos, New Mexico, USA

Alpha magnets are used in a variety of ion-beam and low-energy (< 5 MeV) electron-beam transport systems as both “switchyard” elements and as bunch compressors. A unique feature of the alpha-magnet is its natively achromatic transport. Particles of different energies, injected at a specific location and angle, will exit at the same location and (symmetry-reflected) angle but with a different time-of-flight. Despite the general usefulness of alpha magnets in low-energy beam transport and compression schemes, few simulation codes support them as native elements. The (arguably) most-common codes used for injector design, PARMELA, ASTRA and GPT (listed in order of their release) do not support alpha magnets natively, but do support modeling of space-charge-dominated beams through dipole magnets. As a result, the most commonly used injector design codes are unable to incorporate one of the most useful and interesting beam transport devices. We present a method for simulating an alpha magnet in a tracking code using dipole elements. As elegant supports both dipoles and alpha magnets, it is used to provide a basic check of the approximation and a means of estimating the induced errors.

THP024

High-gradient Cathode Testing for MaRIE

cathode, gun, cavity, laser

739

J.W. Lewellen, F.L. Krawczyk, N.A. Moody
LANL, Los Alamos, New Mexico, USA

X-ray free-electron lasers (X-FELs) provide unprecedented capabilities for characterizing and controlling matter at temporal, spatial and energetic regimes which have been previously inaccessible. The quality of the electron beam is critical to X-FEL performance; a degradation of beam quality by a factor of two, for instance, can prevent the X-FEL from lasing at all, rather than yielding a simple reduction in output power. While conceptual designs for new beam sources exist, they incorporate assumptions about the behavior of the photocathode, under extreme operating conditions. The combined requirements for high bunch charge, short bunch duration, and small emission area, dictate the use of high-efficiency photocathodes operating at electric field gradients of ~140 MV/m. No suitable cathode has been operated at these gradients, however, so the success of next-generation X-FELs rests on a series of untested assumptions. We present our plans to address these knowledge gaps, including the design of a high-gradient RF cavity specifically designed for testing cathodes under MaRIE-relevant conditions.

THP025

Linear Accelerator Design for the LCLS-II FEL Facility

linac, undulator, FEL, laser

743

P. Emma, J.C. Frisch, Z. Huang, H. Loos, A. Marinelli, T.J. Maxwell, Y. Nosochkov, T.O. Raubenheimer, L. Wang, J.J. Welch, M. Woodley
SLAC, Menlo Park, California, USA
J. Qiang, M. Venturini
LBNL, Berkeley, California, USA
A. Saini, N. Solyak
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
The LCLS-II is an FEL facility proposed in response to the July 2013 BESAC advisory committee, which recommended the construction of a new FEL light source with a high-repetition rate and a broad photon energy range from 0.2 keV to at least 5 keV. A new CW 4-GeV electron linac is being designed to meet this need, using a superconducting (SC) L-band (1.3 GHz) linear accelerator capable of operating with a continuous bunch repetition rate up to 1 MHz at ~16 MV/m. This new 700-m linac is to be built at SLAC in the existing tunnel, making use of existing facilities and providing two separate FELs, preserving the operation of the existing FEL, which can be fed from either the existing copper or the new SC linac. We briefly describe the acceleration, bunch compression, beam transport, beam switching, and electron beam diagnostics. The high-power and low-level RF, and cryogenic systems are described elsewhere.

Poster THP025 [0.627 MB]

THP027

LCLS-II Bunch Compressor Study: 5-Bend Chicane

emittance, FEL, radiation, wakefield

755

D. Khan, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

In this paper, we present a potential design for a bunch compressor consisting of 5 bend magnets which is designed to compensate the transverse emittance growth due to Coherent Synchrotron Radiation (CSR). A specific implementation for the second bunch compressor in the LCLS-II is considered. The design has been optimized using the particle tracking code, ELEGANT. Comparisons of the 5-bend chicane’s performance with that of a symmetric 4-bend chicane are shown for various compression ratios and bunch charges. Additionally, a one-dimensional, longitudinal CSR model for the 5-bend design is developed and its accuracy compared against ELEGANT simulations.

Poster THP027 [0.881 MB]

THP031

Further Understanding the LCLS Injector Emittance

emittance, collimation, laser, radiation

774

F. Zhou, K.L.F. Bane, Y. Ding, Z. Huang, H. Loos
SLAC, Menlo Park, California, USA

Funding: US DOE under contract No. DE-AC02-76SF00515
Notable COTR effect from the LCLS laser heater chicane is recently observed at the LCLS injector OTR screen, used for routine emittance measurements. The emittance with the OTR screen is under-estimated by about 30% compared to the values with the wire scanner located next to the OTR screen. The emittance with the OTR and wire scanner is compared and relevant analyses are presented. Slice emittance upstream of the LCLS BC1 is measured using a traditional transverse cavity. Recently, slice emittance downstream of the BC1 is able to be measured with a newly developed technique, using a collimator located in the middle of the BC1. The parasitic effects of using the collimator for slice emittance measurement are evaluated. The slice emittance before and after the BC1 is compared. The dependence of the slice emittance on the linearizer’s transverse offset and CSR effect from the BC1 is discussed.

THP032

Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems

transverse-dynamics, optics, space-charge, simulation

779

R. Li
JLab, Newport News, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed.

THP033

Mechanical Design for a Corrugated Plate Dechirper System for LCLS

wakefield, vacuum, quadrupole, controls

785

M.A. Harrison, P. Frigola, D.W. Martin, A.Y. Murokh, M. Ruelas
RadiaBeam Systems, Santa Monica, California, USA
Z. Huang, R.H. Iverson, T.J. Maxwell, Z. Zhang
SLAC, Menlo Park, California, USA

Funding: This work is supported by Department of Energy grant number DE-SC0009550.
RadiaBeam Systems is developing a novel passive chirp removal system using corrugated plates as studied by Bane and Stupakov.* Following on from low-energy experiments at BNL-ATF,** RBS will install a much larger and powerful system for removing the chirp from the 3-GeV beams in the LTU section at LCLS. The larger plates will present new challenges in the areas of manufacturing and mechanical control. In this paper we review the requirements for the dimensions of the corrugated plates for proper operation and the infrastructure necessary for precisely placing the plates so as not to adversely disrupt the beam.
* K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012
** Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013

THP034

Further Analysis of Corrugated Plate Dechirper Experiment at BNL-ATF

wakefield, simulation, experiment, free-electron-laser

788

M.A. Harrison, G. Andonian, P. Frigola, A.Y. Murokh, M. Ruelas, A.V. Smirnov
RadiaBeam Systems, Santa Monica, California, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by Department of Energy grant number DE-SC0009550.
RadiaBeam Systems successfully completed testing of a proof-of-concept corrugated plate dechirper at the Brookhaven National Laboratory Accelerator Test Facility.* Such passive devices should prove indispensable for the efficient operation of future XFEL facilities. These experiments demonstrated a narrowing of the energy spectrum in chirped beam bunches at 57.6 MeV. In this paper, we compare these results with results from Elegant simulations of the BNL-ATF beam. We also compare GdfidL simulations of the wakefield with the analytic results of Bane and Stupakov.**
* Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
** K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012

THP035

Relativistic Effects in Micro-bunching

bunching, plasma, space-charge, dipole

790

V. Litvinenko
Stony Brook University, Stony Brook, USA
G. Wang
BNL, Upton, Long Island, New York, USA

In this paper we present our theoretical studies of limits on bunching using magnetic systems. We discuss the connection of this limit with plasma oscillations in electron beams and present simple formulae for an additional limit of micro-bunching amplification.

THP036

Benchmark and Simulation Design of a Low Energy Bunch Compressor

gun, simulation, space-charge, focusing

795

A. He, F.J. Willeke, L. Yang, L.-H. Yu
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.

THP041

Development of All-metal Stacked-double Gate Field Emitter Array Cathodes for X-ray Free-electron Laser Applications

emittance, laser, collimation, resonance

811

S. Tsujino, H.-H. Braun, P. Das Kanungo, V. Guzenko, C. Lee, Y. Oh, M. Paraliev
PSI, Villigen PSI, Switzerland
T. Feurer
Universität Bern, Institute of Applied Physics, Bern, Switzerland

Funding: This work was partially supported by the Swiss National Science Foundation Nos. 200020₁43428 and 2000021₁47101.
We report the design, fabrication, and characterization of all-metal stacked-double-gate field emitter array (FEA) cathodes as a potential upgrade option of SwissFEL cathode at the Paul Scherrer Institute. Single-gate FEAs have demonstrated stable operation and gated field emission in pulsed diode gun with gradient up to 30 MV/m with pulse duration down to 200 ps and generation of 5 pC electron bunches by near infrared laser-induced field emission. However for high brightness applications it is crucial to reduce the beam divergence of individual beamlet by a suitable double-gate structure. The challenge lies in suppressing the concomitant decrease of the emission current when a negative focusing potential is applied to the second gate. To solve this problem, a stacked-double-gate FEAs with large collimation gate aperture diameter has been proposed. The intrinsic transverse emittance evaluated from a beam measurement for 1 mm-diameter FEA was below 0.1 mm-mrad. Compatibility with neon-gas conditioning to improve the beam uniformity and high emission current with double-gate FEAs were also demonstrated recently. The current research is focusing on the combination of the surface-plasmon-polariton resonance of the gate electrode and the near infrared laser-induced field emission to realize an ultrafast and ultrabright FEA cathode.

THP044

RF Pulse Flattening in the SwissFEL Test Facility based on Model-free Iterative Learning Control

controls, klystron, feedback, flattop

824

A. Řežaeizadeh, R. Smith
Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland
A. Řežaeizadeh, T. Schilcher
PSI, Villigen PSI, Switzerland

Funding: Paul Scherrer Institut
This paper introduces an iterative approach to producing flat-topped radio frequency (RF) pulses for driving the pulsed linear accelerators in the Swiss free electron laser (SwissFEL). The method is based on model-free iterative learning control which iteratively updates the input pulse shape in order to generate the desired amplitude and phase pulses at the output of the RF system. The method has been successfully applied to the klystron output to improve the flatness of the amplitude and phase pulse profiles.
* P. Janssens,et.al, "Model-free iterative learning control for LTI systems …", 18th IFAC. <CR>
** N. Amann, et.al , "ILC for discrete-time systems …", IEE Control Theory Apps.

THP045

Development of Photocachode Drive Laser System for RF Guns in KU-FEL

laser, FEL, gun, target

828

H. Zen, T. Kii, H. Ohgaki, S. Suphakul
Kyoto University, Kyoto, Japan
R. Kuroda, Y. Taira
AIST, Tsukuba, Ibaraki, Japan

Funding: This research was supported by ZE Research Program, IAE, Kyoto University (ZE26A-22).
We have been developing an accelerator based infrared light sources at Institute of Advanced Energy, Kyoto University. An MIR-FEL has been developed* and a THz-FEL is under development**. A thermionic RF gun has been used as the electron source of MIR-FEL. A project of photocathode upgrade of the current thermionic RF gun is now undergoing to increase the peak power of the FEL. We need to develop multi-bunch laser for this purpose. On the other hand, the THz-FEL will be a single-pass FEL using an S-band 1.6-cell photocathode RF gun. For this purpose, a single-bunch laser is enough. A photocathode drive laser system for those purposes has been developed. The laser system consists of an Nd:YVO4 mode-locked oscillator with an integrated AOM, a laser pointing stabilizer, two diode pumped Nd:YAG amplifiers, and harmonic generators. In case of single-bunch operation of the laser, the pulse energy of higher than 150 micro-J at 266 nm has been obtained. For multi-bunch operation, 70 micro-J/micro-pulse and 70 pulses have been obtained. Optimization for multi-bunch operation of the laser is under going. In the conference, status of development of the drive laser will be presented.
*H. Zen, et al., Infrared Physics & Technology, vol. 51, pp.382-385 (2008).
**S. Suphakul, et al., in this conference.

THP048

Formation of the Electron Bunch Longitudinal Profile for Coherent Electron Cooling Experiment

cavity, gun, experiment, laser

840

I. Pinayev, D. Kayran, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Proof-of-princilpe experiment of the coherent electron cooling is ongoing at Brookhaven National Lab. CeC mechanism utilizes amplification of density modulation, induced by hadrons, by an FEL structure. To fully utilize electron beam cooling capacity we need uniform longitudinal beam profile. In this paper we present two frequency injector system tuned for this requirement.

THP053

Steady State Multipacting in a Micro-pulse Electron Gun

cavity, cathode, experiment, gun

851

K. Zhou, X.Y. Lu, X. Luo, S.W. Quan, Z.Q. Yang, J. Zhao
PKU, Beijing, People's Republic of China

Multipacting is a resonant electron discharge phenomenon via secondary electron emission, while micro-pulse electron gun (MPG) utilizes the multipacting current in a radio-frequency (RF) cavity to produce short pulse electron beams. The concept of MPG has been proposed for many years. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady state mulitpacting in a MPG. The requirements for steady state multipacting are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed and constructed. Various kinds of grid-anodes are tested in our primary experiments. Both the unstable and stable multipacting current have been observed. Presently, the stable output beam current has been detected at about 12.2 mA. Further experimental study is under way now.

Poster THP053 [2.525 MB]

THP054

Dark Current Studies at the APEX Photoinjector

gun, cathode, simulation, solenoid

855

R. Huang
USTC/NSRL, Hefei, Anhui, People's Republic of China
D. Filippetto, C. F. Papadopoulos, F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The increasing scientific demand for a high repetition rate FEL light source is driving the development of electron sources with high beam quality, delivering electron bunches at rates in the MHz range. An ongoing project to develop such a source is the Advanced Photoinjector Experiment (APEX) at LBNL. High brightness electron beams require high fields at the cathode during the electron emission. Such high fields associated with imperfections on the cathode surface area can induce undesired electron field emission (dark current). Excessive dark current can generate quenching of SRF structures and undesired radiation doses activating accelerator components and damaging undulator structures. In the present paper, we discuss the dark current studies performed at APEX. Field emitters in the cathode area have been localized and characterized, and techniques for minimizing dark current emission and to passively remove it have been investigated.

THP057

Longitudinal and Transverse Optimization for a High Repetition Rate Injector

gun, emittance, cavity, brightness

864

C. F. Papadopoulos, D. Filippetto, R. Huang, G.J. Portmann, H.J. Qian, F. Sannibale, S.P. Virostek, R.P. Wells
LBNL, Berkeley, California, USA
A.C. Bartnik, I.V. Bazarov, B.M. Dunham, C.M. Gulliford, C.E. Mayes
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Brachmann, D. Dowell, P. Emma, Z. Li, T.O. Raubenheimer, J.F. Schmerge, T. Vecchione, F. Zhou
SLAC, Menlo Park, California, USA
A. Vivoli
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The injector is the low energy part of a linac, where space charge and kinematic effects may affect the electron beam quality significantly, and in the case of single pass systems determines the brightness in the downstream components. Following the increasing demand for high repetition rate user facilities, the VHF-gun, a normal conducting, high repetition rate (1 MHz) RF gun operating at 186 MHz has been constructed at LBNL within the APEX project and is under operation. In the current paper, we report on the status of the beam dynamics studies. For this, a multi-objected approach is used, where both the transverse and the longitudinal phase space quality is optimized, as quantified by the transverse emittance and the bunch length and energy spread respectively. We also report on different bunch charge operating modes.

THP058

Solid-State Switch for a Klystron Modulator for Stable Operation of a THz- FEL

FEL, klystron, operation, linac

868

G. Isoyama, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, R. Kato, K. Kawase, K. Miyazaki, A. Tokuchi, R. Tsutsumi, M. Yaguchi
ISIR, Osaka, Japan
F. Kamitsukasa
Osaka University, Graduate School of Science, Osaka, Japan

We have been conducting studies on upgrade of the THz-FEL and its applications, using the L-band electron linac at ISIR, Osaka University. The stability of the FEL is crucial for these studies and the operation of the FEL depends on characteristics of the electron beam, especially on stability of the electron energy, which is strongly affected by the RF power and its phase provided to the linac. We uses a klystron modulator with the a highly stable charging system to the PFN with a fractional variation of 8×10^-5 (peak-to-peak), but the klystron voltage varies by one order of magnitude larger due probably to the thyratron used as a high voltage and high current switch in the klystron modulator. In order to make the stability of the FEL higher, we have developed a solid-state switch using static induction thyristors. The performance of the switch is as follows; the maximum holding voltage is 25 kV, the maximum current is 6 kA for the pulse duration of 10 us, the switching time is 270 ns, and the maximum repetition frequency is 10 Hz. The intensity fluctuation of the FEL macropulse is reduced to a few percents using the solid state switch.

THP059

The Laser Heater System of SwissFEL

laser, undulator, emittance, operation

871

M. Pedrozzi, M. Calvi, R. Ischebeck, S. Reiche, C. Vicario
PSI, Villigen PSI, Switzerland
B.D. Fell, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Short wavelength FELs are generally driven by high-brilliance photo-cathode RF-guns which generate electron beams with an uncorrelated energy spread on the order of 1 keV or less. These extremely cold beams can easily develop micro-bunching instabilities caused by longitudinal space charge forces after the compression process. This can result in a blow up of the energy spread and emittance beyond the tolerable level for SASE emission. It has been demonstrated theoretically and experimentally [1] that a controlled increase of the uncorrelated energy spread to typically a few keV is sufficient to strongly reduce the instability growth. In the laser heater system, one achieves a controlled increase of the beam energy spread by a resonant interaction of the electron beam with a transversally polarized laser beam inside of an undulator magnet. The momentum modulation resulting from the energy exchange within the undulator is consequently smeared out in the transmission line downstream of the laser heater system. In SwissFEL, the laser heater system is located after the first two S-band accelerating structures at a beam energy of 150 MeV. This paper describes the layout and the sub-components of this system.
[1] Z. Huang, et al, Phys. Rev. Special Topics – Accelerator and beams 13, 020703 (2010)

THP060

Design of a Spatio-temporal 3-D Ellipsoidal Photo Cathode Laser System for the High Brightness Photo Injector PITZ

laser, cathode, simulation, photon

878

T. Rublack, J.D. Good, M. Khojoyan, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
IAP/RAS, Nizhny Novgorod, Russia
I. Hartl, S. Schreiber
DESY, Hamburg, Germany
E. Syresin
JINR, Dubna, Moscow Region, Russia

Funding: German Federal Ministry of education and Research, project 05K10CHE “Development and experimental test of a laser system for producing quasi 3D ellipsoidal laser pulses” and RFBR grant 13-02-91323.
Minimized emittance is crucial for improved operation of linac-based free electron lasers. Simulations have thus shown 3-D ellipsoidal photocathode laser pulses are superior to the standard Gaussian or cylindrical laser pulses in this manner. Therefore, in collaboration with the Joint Institute of Nuclear Research (JINR, Dubna, Russia) and the Photo Injector Test facility at DESY, Zeuthen (PITZ), a prototype system capable of producing spatio-temporal 3-D ellipsoidal pulses has been constructed at the Institute of Applied Physics (IAP, Nizhny Novgorod, Russia). The system consists of a dual-output, 1030 nm fiber laser coupled with disc amplifiers, a scheme based on Spatial Light Modulators for spatial and temporal pulse shaping of the primary output, a cross-correlator set up utilizing the secondary output to characterize the primary output, and finally frequency conversion to the UV. A preliminary, temporal ellipsoidal shaped IR pulse has been observed and measured so far at IAP RAS. As of writing, improvements and refinements of the system are ongoing and it is expected to replicate the finalized prototype at PITZ soon.

THP069

Performance Study of High Bandwidth Pickups Installed at FLASH and ELBE for Femtosecond-Precision Arrival Time Monitors

pick-up, laser, operation, experiment

893

M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
DESY, Hamburg, Germany
A. Angelovski, R. Jakoby, A. Penirschke
TU Darmstadt, Darmstadt, Germany
M. Gensch, M. Kuntzsch
HZDR, Dresden, Germany
M. Kuntzsch
TU Dresden, Dresden, Germany
T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

At today's free-electron lasers, high-resolution electron bunch arrival time measurements have become increasingly more important in fast feedback systems for a timing jitter reduction down to the femtosecond level as well as for time-resolved pump-probe experiments. This is fulfilled by arrival time monitors which employ an electro-optical detection scheme by means of synchronised ultrashort laser pulses. Even more, at FLASH and the European XFEL the measurement has to cover a wide range of bunch charges from 1 nC down to 20 pC with equally sub-10 fs resolution. To meet these requirements, recently a high bandwidth pickup electrode with a cut-off frequency above 40 GHz has been developed. These pickups are installed at the macro-pulsed SRF accelerator of the free-electron laser FLASH and at the macro-pulsed continuous wave SRF accelerator ELBE. In this paper we present an evaluation of the pickup performance by direct signal measurements with high bandwidth oscilloscopes and by use of the electro-optical arrival time monitor.

THP070

A Tool for Real Time Acquisitions and Correlation Studies at FERMI

FEL, controls, GUI, TANGO

898

E. Allaria, W.M. Fawley, E. Ferrari
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy

In this work we report the recent implementation of a Matlab based acquisition program that, exploiting the real time capabilities of TANGO, can be used at FERMI for acquiring various machine parameter and electron beam properties together with most FEL signals. Analysis of the saved datafiles is performed with a second code that allows to retrieve correlations and to study dependence of FEL properties on machine parameters. An overview of the two codes is reported.

THP074

Infrared Diagnostics Instrumentation Design for the Coherent Electron Cooling Proof of Principle Experiment

wiggler, FEL, ion, experiment

905

T.A. Miller, D.M. Gassner, V. Litvinenko, M.G. Minty, I. Pinayev, B. Sheehy
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The Coherent Electron Cooling Proof-of-Principle experiment [*] based on an FEL is currently under construction in the RHIC tunnel at BNL. Diagnostics for the experimental machine [**] are currently being designed, built and installed. This paper focuses on the design of the infrared diagnostic instrumentation downstream of the three tandem 2.8m long helical wiggler sections that will act on a 22MeV 68uA electron beam co-propagating with the 40GeV/u RHIC gold beam. The 14 um FEL radiation, or wiggler light, will be extracted from RHIC via a viewport in a downstream DX magnet cryostat and analysed by instrumentation on a nearby optics bench. Instruments concentrating on three parameters, namely intensity, spectral content, and transverse profile, will extract information from the wiggler light in an attempt to quantify the overlap of the electron and ion beams and act as an indicator of coherent cooling.
* V. Litvinkenko, et al THOBN3, PAC2011, New York, NY
** D. M. Gassner, et al WEAP01, BIW2012, Newport News, VA

THP075

Design of TDS-based Multi-screen Electron Beam Diagnostics for the European XFEL

kicker, emittance, operation, timing

909

J. Wychowaniak
TUL-DMCS, Łódź, Poland
C. Gerth, M. Yan
DESY, Hamburg, Germany

Dedicated longitudinal electron beam diagnostics is essential for successful operation of modern free-electron lasers. Demand for diagnostic data includes the longitudinal bunch profile, bunch length and slice emittance of the electron bunches. Experimental setups based on transverse deflecting structures (TDS) are excellent candidates for this purpose. At the Free-Electron Laser in Hamburg (FLASH), such a longitudinal bunch profile monitor utilizing a TDS, a fast kicker magnet and an off-axis imaging screen, has been put into operation. It enables the measurement of a single bunch out of a bunch train without affecting the remaining bunches. At the European X-ray Free-Electron Laser (XFEL) multiscreen stations in combination with TDS are planned to be installed. In order to allow for flexible measurements of longitudinal bunch profile and slice emittance, a configurable timing and trigger distribution to the fast kicker magnets and screen stations is required. In this paper, we discuss various operation patterns and the corresponding realization based on MTCA.4 technology.

THP076

Measurements of the Timing Stability at the FLASH1 Seeding Experiment

laser, experiment, timing, FEL

913

C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz
DESY, Hamburg, Germany
G. Angelova Hamberg
Uppsala University, Uppsala, Sweden
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany
P.M. Salen, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355.
For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.

THP082

Measurements of Compressed Bunch Temporal Profile using Electro-Optic Monitor at SITF

laser, vacuum, diagnostics, optics

922

Ye. Ivanisenko, V. Schlott
PSI, Villigen PSI, Switzerland
P. Peier
DESY, Hamburg, Germany

Funding: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.°290605 (PSI-FELLOW/COFUND)
The SwissFEL Injector Test Facility (SITF) is an electron linear accelerator with a single bunch compression stage at Paul Scherrer Institute (PSI) in Switzerland. Electro-optic monitors (EOMs) are available for bunch temporal profile measurements before and after the bunch compressor. The profile reconstruction is based upon spectral decoding technique. This diagnostic method is non-invasive, compact and cost-effective. It does not have high resolution and wide dynamic range of an RF transverse deflecting structure (TDS), but it is free of transverse beam size influence, what makes it a perfect tool for fast compression tuning. We present results of EOM and TDS measurements with down to 150 fs long bunches after the compression stage at SITF.

THP083

Coherent Radiation Diagnostics for Longitudinal Bunch Characterization at European XFEL

radiation, detector, feedback, diagnostics

925

P. Peier, H. Dinter, C. Gerth
DESY, Hamburg, Germany

European XFEL comprises a 17.5 GeV linear accelerator for the generation of hard X-rays. Electron bunches from 20 pC to 1 nC will be produced with a length of a few ps in the RF gun and compressed by three orders of magnitude in three bunch compressor (BC) stages. European XFEL is designed to operate at 10 Hz delivering bunch trains with up to 2700 bunches separated by 222 ns. The high intra-bunch train repetition rate offers the unique possibility of stabilizing the machine with an intra-bunch train feedback, which puts in turn very high demand on fast longitudinal diagnostics. Two different systems will be installed in several positions of the machine. Five bunch compression monitors (BCM) will monitor the compression factor of each BC stage and used for intra-bunch train feedbacks. A THz spectrometer will be used to measure parasitically the longitudinal bunch profile after the energy collimator at 17.5 GeV beam energy. We will present concepts for fast longitudinal diagnostic for European XFEL based on coherent radiation, newest developments for high repetition rate measurements and simulations for the feedback capability of the system.

THP084

Longitudinal Diagnostics of RF Electron Gun using a 2-cell RF Deflector

gun, cavity, laser, experiment

929

M. Nishiyama, K. Sakaue, T. Takahashi, T. Toida, M. Washio
Waseda University, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.
We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are using this high quality electron bunch for many application researches. It is necessary to measure the bunch length and temporal distribution for evaluating application researches and for improving an rf gun itself. Thus we adopted the rf deflector system. It kicks the electron bunch with resonated rf electromagnetic field. Using this technique, the longitudinal distribution is mapped into the transverse space. The rf deflector has a 2-cell standing wave π-mode structure, operating in TM120 dipole mode at 2856 MHz. It provides a maximum vertical kick of 1.00MV with 750 kW input rf-power which is equivalent to the temporal resolution of around 58 femtoseconds bunch length. In this conference, we report the details of our rf deflector, the latest progress of longitudinal phase space diagnostics and future prospective.

THP087

Electron Beam Diagnostics for COXINEL

diagnostics, undulator, plasma, FEL

937

M. Labat, C. Bourassin-Bouchet, L. Cassinari, M.-E. Couprie, M.E. El Ajjouri, N. Hubert, A. Loulergue
SOLEIL, Gif-sur-Yvette, France

On the path towards more compact free electron lasers (FELs), the project COXINEL was recently funded: a transfer line will be installed to adapt a plasma accelerated beam (from LOA) into an in-vacuum undulator built by SOLEIL. This experiment should enable to demonstrate the first FEL based on a plasma accelerator. Because plasma beams are intrinsically very different from RF acceletor beams (much shorter, divergent and smaller with a higher energy spread and energy jitter), their transport and matching in the undulator is critical if willing to obtain a significant amplification. This is why special care has to be taken in the design of the beam diagnostics to be able to measure the transverse beam sizes, energy spread and jitter, emittance and bunch length. For these purposes, several diagnostics will be implemented from the plasma accelerator exit down to the undulator exit. In each station, several screen types will be available and associated to high resolution imaging screens. In this paper, we present the experimental layout and associated simulation of the diagnostics performances.

THP091

Design and Test of Wire-Scanners for SwissFEL

vacuum, FEL, monitoring, booster

948

G.L. Orlandi, M. Baldinger, H. Brands, P. Heimgartner, R. Ischebeck, A. Kammerer, F. Löhl, R. Lüscher, P. Mohanmurthy, C. Ozkan, B. Rippstein, V. Schlott, L. Schulz, C. Seiler, S. Trovati, P. Valitutti, D. Zimoch
PSI, Villigen PSI, Switzerland

The SwissFEL light-facility will provide coherent X-rays in the wavelength region 7-0.7 nm and 0.7-0.1 nm. In SwissFEL, view-screens and wire-scanners will be used to monitor the transverse profile of a 200/10pC electron beam with a normalized emittance of 0.4/0.2 mm.mrad and a final energy of 5.7 GeV. Compared to view screens, wire-scanners offer a quasi-non-destructive monitoring of the beam transverse profile without suffering from possible micro-bunching of the electron beam. The main aspects of the design, laboratory characterization and beam-test of the SwissFEL wire-scanner prototype will be presented.

THP092

Transition Radiation of an Electron Bunch and Imprint of Lorentz-Covariance and Temporal-Causality

radiation, diagnostics, optics, simulation

952

G.L. Orlandi
PSI, Villigen PSI, Switzerland

The study of Transition Radiation (TR) of a bunch of N electrons offers a precious insight into the role that Lorentz-covariance and temporal-causality play in an electromagnetic radiative mechanism of a relativistic beam. The contributions of the N single electrons to the radiation field are indeed characterized by emission phases from the metallic surface which are in a causality relation with the temporal sequence of the N particle collisions onto the radiating screen. The Lorentz-covariance characterizing the virtual quanta field of the relativistic charge is also expected to imprint the radiation field and the related energy spectrum. The main aspects of a Lorentz-covariance and temporal-causality consistent formulation of the TR energy spectrum of an electron bunch will be described.

THP093

Coherent Electron Cooling Proof of Principle Phase 1 Instrumentation Status

detector, instrumentation, status, electronics

956

D.M. Gassner, J.C. Brutus, R.L. Hulsart, V. Litvinenko, R.J. Michnoff, T.A. Miller, M.G. Minty, I. Pinayev, M. Wilinski
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The purpose of the Coherent electron Cooling Proof-of- Principle (CeC PoP) [1] experiment being designed at RHIC is to demonstrate longitudinal (energy spread) cooling before the expected CD-2 for eRHIC. The scope of the experiment is to longitudinally cool a single bunch of 40 GeV/u gold ions in RHIC. The cooling facility will be installed inside the RHIC tunnel in 3 phases. The status of the instrumentation systems planned for phase 1 commissioning efforts will be described. This paper will also describe updates to the instrumentation systems proposed to meet the diagnostics challenges during the final phase of cooling commissioning [2]. These include measurements of beam intensity, emittance, energy spread, bunch length, position, and transverse alignment of electron and ion beams.

THP095

Evolvement of the Laser and Synchronization System for the Shanghai DUV-FEL Test Facility

laser, FEL, experiment, free-electron-laser

960

B. Liu, L. Feng, T. Lan, X.Q. Liu, D. Wang, X.T. Wang, W.Y. Zhang, S.P. Zhong
SINAP, Shanghai, People's Republic of China

Funding: supported by the National Natural Science Foundation of China (Grant No. 11175241)
Many attractive experiments including HGHG, EEHG, cascaded HGHG, chirped pulse amplification etc. are carried out or planned on the Shanghai Deep Ultra-Violet Free Electron Laser test facility. These experiments are all utilizing a laser as seed, and need precise synchronization between the electron beam and the laser pulse. We will describe the history and current status of the seeding and synchronization scheme for the SDUV-FEL together with some related experiment results in this paper.

THP097

Longitudinal Response Matrix Simulations for the SwissFEL Injector Test Facility

diagnostics, simulation, laser, free-electron-laser

964

Á. Saá Hernández, F. Frei, R. Ischebeck
PSI, Villigen PSI, Switzerland
B. Beutner
DESY, Hamburg, Germany

The Singular Value Decomposition (SVD) method has been applied to the SwissFEL Injector Test Facility to identify and better expose the various relationships among the possible jitter sources affecting the longitudinal phase space distribution and the longitudinal diagnostic elements that measure them. To this end, several longitudinal tracking simulations have been run using the Litrack code. In these simulations the RF and laser jitter sources are varied one-by-one within a range spanning twice their expected stability. The particle distributions have been dumped at the diagnostic locations and the measured quantities analyzed. A matrix has been built by linearly fitting the response of each measured quantity to each jitter source. This response matrix is normalized to the jitter source stability and the instrumentation accuracy, and it is inverted and analyzed using SVD. From the eigenvalues and eigenvectors the sensitivity of the diagnostics to the jitters can be evaluated and their specifications and locations optimized.

THC02

Thermal Emittance Measurements at the SwissFEL Injector Test Facility

emittance, cathode, laser, gun

970

E. Prat, S. Bettoni, H.-H. Braun, M.C. Divall, R. Ganter, C.P. Hauri, T. Schietinger, A. Trisorio, C. Vicario
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

In a laser-driven RF-gun the ultimate limit of the beam emittance is the transverse momentum of the electrons as they exit the cathode, the so-called intrinsic or thermal emittance. In this contribution we present measurements of the thermal emittance at the SwissFEL Injector Test Facility for electron beam charges down to a few tens of fC. We have studied the thermal emittance and QE dependence on the laser wavelength, the RF-gun gradient and the cathode material (Cu and Cs2Te).

Slides THC02 [1.063 MB]

FRA04

Optimization of High Average Power FEL Beam for EUV Lithography Application

FEL, laser, plasma, optics

990

A. Endo, K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
H. Mizoguchi
Gigaphoton Inc, Hiratsuka, Kanagawa, Japan

Extreme Ultraviolet Lithography (EUVL) is realized with 100W plasma EUV source at 13.5nm. It is recommended by the EUVL community to evaluate an alternative approach based on high repetition rate FEL, to avoid the power limit of the plasma source. Several papers discuss on the possibility to realize superconducting FEL to generate multiple kW 13.5nm light. We must notice that the present SASE FEL pulse has higher beam fluence than the resist ablation threshold*, and high spatial coherence which results in speckle patterns, and random longitudinal mode beat which leads to high peak powerμspikes. An expanding mirror is installed after the undulator to reduce the beam fluence, external-seeding configuration is employed to reduce the longitudinal mode beat, and total reflection beam homogenizer is used for spatial mode mixing. Pulse repetition rate is more than 3MHz to cancel the speckle patter formation by averaging illumination. This paper discusses on the lowest risk approach to construct a prototype to demonstrate a high average power 13.5nm FEL for the best optimization in EUVL application, including the scaling to 6.7nm wavelength.
*J. Chalupský, L. Juha et.al, “Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic molecular solids”, OPTICS EXPRESS 15, 6036 (2007)

Slides FRA04 [1.413 MB]

FRB02

A Collinear Wakefield Accelerator for a High Repetition Rate Multi-beamline Soft X-ray FEL Facility

wakefield, FEL, acceleration, emittance

993

A. Zholents, W. Gai, R.R. Lindberg, J.G. Power, Y.-E. Sun
ANL, Argonne, Ilinois, USA
C.-J. Jing, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
C. Li, C.-X. Tang
TUB, Beijing, People's Republic of China
D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Supported by U.S. Department of Energy under Contract No. DE-AC02-06CH11357 and by the U.S. Department of Energy Laboratory LDRD program at Los Alamos National Laboratory.
A concept is presented for a multi beamline soft x-ray free-electron laser (FEL) facility where several FEL undulator lines are driven by an equal number of high repetition rate single-stage collinear wakefield accelerators (CWA). A practical design of the CWA, extending over 30 meters and embedded into a quadrupole wiggler, is considered. The wiggler’s structure of alternating focusing and defocusing quadrupoles is used to control single-bunch breakup instability. It is shown that practical restrictions on the maximum attainable quadrupole field limit the maximum attainable charge in the drive bunch whose sole purpose is to produce a high accelerating field in the CWA for the following main bunch. It is also pointed out that the distance between drive and main bunches varies along the accelerator, causing a measurable impact on the energy gain by the main bunch and on the energy spread of electrons in it. Means to mitigate these effects are proposed and results are presented for numerical simulations demonstrating the main bunch with plausible parameters for FEL application including a relatively small energy spread. Finally, results are presented for the expected FEL performance using an appropriately chosen undulator.

Slides FRB02 [6.512 MB]