FEL2013 - Table of Session: MOPSO (New Lasings, Beam Physics, Novel Concepts & Theory)

Paper	Title	Page
MOPSO02	Measurement of Electron-Beam and Seed Laser Properties Using an Energy Chirped Electron Beam	24
	E. Allaria, G. De Ninno, S. Di Mitri, W.M. Fawley, E. Ferrari, L. Fröhlich, G. Penco, P. Sigalotti, S. Spampinati, C. Spezzani, M. Trovò Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy G. De Ninno, S. Spampinati University of Nova Gorica, Nova Gorica, Slovenia E. Ferrari Università degli Studi di Trieste, Trieste, Italy
	We present a new method that uses CCD images of the FERMI electron beam at the dump spectrometer after the undulator to determine various electron beam and external seed laser properties. By taking advantage of the correlation between time and electron beam energy for a quasi-linearly chirped electron beam and the fact that the FERMI seed laser pulse (~180 fs) is much shorter than the electron beam duration (~1 ps), measurements of the e-beam pulse length and temporally local energy chirp and current are possible. Moreover, the scheme allows accurate determination of the timing jitter between the electron beam and the seed laser, as well as a measure of the latter's effective pulse length in the FEL undulators. The scheme can be also provide an independent measure of the energy transferred from the electron beam to the FEL output radiation. We describe the proposed method as well as some experimental results obtained at the seeded FERMI FEL.

MOPSO04	Theoretical Analysis of a Laser Undulator-Based High Gain FEL	27
	P. Baxevanis, R.D. Ruth SLAC, Menlo Park, California, USA
	The use of laser (or RF) undulators is nowadays considered attractive for FEL applications, particularly those that aim to utilize relatively low-energy electron beams. In the context of the standard theoretical analysis, the counter-propagating laser pulse is usually treated in the plane-wave approximation, neglecting amplitude and phase variation. In this paper, we develop a three-dimensional, analytical theory of a high-gain FEL based on a laser or RF undulator, taking into account the longitudinal variation of the undulator field amplitude, the laser Gouy phase and the effects of emittance and energy spread in the electron beam. Working in the framework of the Vlasov-Maxwell formalism, we derive a self-consistent equation for the radiation amplitude in the linear regime, which is then solved to good approximation by means of an orthogonal expansion technique []. Numerical results obtained from our analysis are used in the study of an example of a compact, laser undulator-based, X-ray FEL. P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).

MOPSO06	Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method	32
	D. A. Bizzozero, J.A. Ellison, K.A. Heinemann, S.R. Lau UNM, Albuquerque, New Mexico, USA
	Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico. We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study. * See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2. ** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012).

MOPSO07	Channeling Radiation With Low-Energy Electron Beams: Experimental Plans and Status at Fermilab	38
	B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot Northern Illinois University, DeKalb, Illinois, USA C.A. Brau, B.K. Choi, B.L. Ivanov, M.H. Mendenhall Vanderbilt University, Nashville, TN, USA W.E. Gabella Vanderbilt University, W.M. Keck Foundation Free-Electron Laser Center, Nashville, USA W.S. Wagner Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
	Funding: This work was supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 with Vanderbilt University and Northern Illinois University. Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams. In this contribution we describe the anticipated performance and preliminary results from a channeling radiation experiment to produce ~ 1.2-keV radiation from a ~ 4-MeV electron beam at Fermilab's high-brightness electron source lab(HBESL). We also discuss plans to produce X-ray radiation ([10,80]-keV photon energy) at Fermilab's advanced superconducting test accelerator (ASTA).

MOPSO08	Unaveraged Modelling of a LWFA Driven FEL	43
	L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom F.J. Grüner, A.R. Maier CFEL, Hamburg, Germany F.J. Grüner, A.R. Maier Uni HH, Hamburg, Germany F.J. Grüner LMU, Garching, Germany
	Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed. [1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012)

MOPSO09	Investigation of a 2-Colour Undulator FEL Using Puffin	47
	L.T. Campbell, B.W.J. MᶜNeil USTRAT/SUPA, Glasgow, United Kingdom S. Reiche PSI, Villigen PSI, Switzerland
	The unaveraged FEL code Puffin* is used to investigate a 2 color FEL. In the scheme under investigation, undulator modules are tuned alternately to generate 2 frequencies quasi-simultaneously, which should result in greater stability than generating them consecutively. The advantage of using Puffin is that it provides the capability of modelling a broad bandwidth spectrum. For example, radiation at 1nm and 2.4nm is difficult to model simultaneously in standard averaged FEL codes. An unaveraged code like Puffin is able to model 2 (or more) wavelengths with a much wider spacing. * LT Campbell and BWJ McNeil, Phys. Plasmas 19, 093119 (2012)

MOPSO17	The Present Status of the Theory of the FEL-based Hadron Beam Cooling	52
	A. Elizarov, V. Litvinenko 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 (CeC)* device is one of the new facilities under construction in BNL. The CeC is a realization of the stochastic cooling with an electron beam serving as a pick-up and kicker. Hadrons generate electron density perturbations in the modulator section, then these perturbations are amplified in an FEL, and then, they accelerate (or decelerate) hadrons in the kicker by electric field with respect to their velocities. Here we present the theoretical description of the modulator sector,, where the electron density perturbations are formed and our new results on the time evolution of these perturbations in the FEL section, where they are amplified. V. N. Litvinenko, Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009). A. Elizarov, V. Litvinenko, G. Wang, IPAC'12, weppr099 (2012). * A. Elizarov, V. Litvinenko, IPAC'13, mopwo088 (2013).

MOPSO27	Study of CSR Effects in the Jefferson Laboratory FEL Driver	58
	C.C. Hall, S. Biedron, T.A. Burleson, S.V. Milton, A.L. Morin CSU, Fort Collins, Colorado, USA S.V. Benson, D. Douglas, P.E. Evtushenko, F.E. Hannon, R. Li, C. Tennant, S. Zhang JLAB, Newport News, Virginia, USA B.E. Carlsten, J.W. Lewellen LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work also received supported under U.S. DOE Contract No. DE-AC05-06OR23177. In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped.

MOPSO30	Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation	63
	J. Hebling, G. Almási, J.A. Fülöp, M.I. Mechler, Z. Tibai, Gy. Tóth University of Pecs, Pécs, Hungary
	Funding: Work supported by Hungarian Research Fund (OTKA), grant number 101846, and from SROP-4.2.1.B-10/2/KONV-2010-0002 and SROP-4.2.2/B-10/1-2010-0029 Robust methods for producing waveform-controlled half-cycle–few-cycle pulses in the mid-infrared (MIR)–extreme ultraviolet (EUV) spectral range are proposed. They are based on coherent Thomson scattering of THz pulses on relativistic ultrathin electron layers and coherent undulator radiation of relativistic ultrathin electron layers, respectively. The ultrathin electron layers are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers if a single-period modulator undulator with period length significantly shorter than the resonant one is used and the undulator parameter is only K=0.25. Thomson scattering of THz pulses on ultrathin electron layers with only 50 MeV energy can generate for example 170 as long single-cycle pulses at 80 nm wavelength with 0.1 nJ energy. Coherent undulator radiation of ultrathin electron layers with 450 MeV energy can generate single-cycle radiation in the 20 nm – 1000 nm wavelength range. The corresponding pulse energy and pulse duration vary in the 10 pJ – 2 nJ and 47 as – 2.1 fs ranges, respectively.

MOPSO31	Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave	762
	K.A. Heinemann, J.A. Ellison UNM, Albuquerque, New Mexico, USA M. Vogt DESY, Hamburg, Germany
	Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY. We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds. * J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph]

MOPSO34	Highly Efficient, High-energy THz Pulses from Cryo-cooled Lithium Niobate for Accelerator and FEL Applications	68
	K.-H. Hong, E. Granados, S.-W. Huang, W.R. Huang, F.X. Kaertner, R. Koustuban, L.E. Zapata MIT, Cambridge, Massachusetts, USA F.X. Kaertner CFEL, Hamburg, Germany
	Funding: This work was supported by DARPA under contract N66001-1-11-4192. Intense, ultrafast THz fields are of great interest for electron acceleration, beam manipulation and measurement, and pump-probe experiments with coherent soft/hard x-ray sources based on FELs or inverse Compton scattering sources. Acceleration at THz frequencies has an advantage over RF in terms of accessing high electric-field gradients (>100 MV/cm), while the beam delivery can be treated quasi-optically. However, high-field THz pulse generation is still demanding when compared with conventional RF generation. In this paper, we present highly efficient, single-cycle, 0.45 THz pulse generation by optical rectification of 1.03 μm pulses in cryogenically cooled lithium niobate (LN). Using a near-optimal duration of 680 fs and a pump energy of 1.2 mJ, we report conversion efficiencies above 3% [1], >10 times higher than previous report (0.24%) [2]. Cryogenic cooling of lithium niobate significantly reduces the THz absorption, which will enable the scaling of THz pulse energies to the mJ. We will also report on polarization and mode conversion using segmented THz waveplates to generate radially-polarized TEM01 modes, suitable for THz electron acceleration in dielectric waveguide. [1] S.-W. Huang et al., Opt. Lett. 38, 796-798 (2013). [2] J. A. Fülöp et al., Opt. Lett. 37, 557-559 (2012).

MOPSO40	CLARA Accelerator Design and Simulations	72
	P.H. Williams, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Science & Technology Facilities Council We present the accelerator design for CLARA (Compact Linear Advanced Research Accelerator) at Daresbury Laboratory. CLARA will be a testbed for novel FEL configurations. The accelerator will consist of an RF photoinjector, S-band acceleration and transport to 250MeV including X-band linearisation and magnetic bunch compression. We describe the transport in detail. Beam dynamics simulations are then used to define a set of operating working points suitable for the different FEL schemes intended to be tested on CLARA.

MOPSO43	High Power Laser Transport System for Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns	75
	J.M.D. Kowalczyk, M.R. Hadmack, J. Madey, E.B. Szarmes, M.H.E.H. Vinci University of Hawaii, Honolulu, HI, USA
	Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03. Heat from a high power, short pulse laser deposited on the surface of a thermionic electron gun cathode will diffuse into the bulk producing a surface cooling effect that counteracts the electron back-bombardment (BB) heating intrinsic to the gun. The resulting constant temperature stabilizes the current allowing extension of the gun’s peak current and duty cycle. To enable this laser cooling, high power laser pulses must be transported to the high radiation zone of the electron gun, and their transverse profile must be converted from Gaussian to top-hat to uniformly cool the cathode. A fiber optic transport system is simple, inexpensive, and will convert a Gaussian to a top-hat profile. Coupling into the fiber efficiently and without damage is difficult as tight focusing is required at the input and, if coupled in air, the high fluence will breakdown the air resulting in lost energy. We have devised a vacuum fiber coupler (VFC) that allows the focus to occur in vacuum, avoiding the breakdown of air, and have successfully transported 10 ns long, 85 mJ pulses from a 1064 nm Nd:YAG laser through 20 m of 1 mm diameter fiber enabling testing of the laser cooling concept.

MOPSO44	Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns	79
	J.M.D. Kowalczyk, M.R. Hadmack, J. Madey University of Hawaii, Honolulu, HI, USA
	Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03. A theoretical study of the use of laser cooling to counteract electron back-bombardment heating (BB) in thermionic electron guns is presented. Electron beams with short bunches, minimum energy spread, and maximum length pulse trains are required for many applications, including the inverse-Compton X-ray source being developed at UH. Currently, these three electron beam parameters are limited by BB which causes the cathode temperature and emission current to increase leading to beam loading. Beam loading elongates the bunches by shifting the electrons’ relative phases, introduces energy spread by reducing the energy of electrons emitted later in the macropulse, and forces the use of shorter macropulses to minimize energy spread. Irradiation of the electron gun cathode with a short laser pulse prior to beam acceleration allows the laser heat to diffuse into the cathode bulk effectively cooling the surface and counteracting the BB. Calculation of the the cooling produced by laser pulses of various duration and energy is presented.

MOPSO49	Numerical Accuracy When Solving the FEL Equations	82
	R.R. Lindberg ANL, Argonne, USA
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 The usual method of numerically solving the FEL equations involves dividing both the e-beam and radiation field into "slices" that are loaded one at a time into memory. This scheme is only first order accurate in the discretization of the ponderomotive phase because having only one slice in memory effectively results in a first order interpolation of the field-particle coupling. While experience has shown that FEL simulations work quite well, the first order accuracy opens the door to two possible ways of speeding up simulation time. First, one can consider higher order algorithms; unfortunately, these methods appear to require all the particle and field data in memory at the same time, and therefore will typically only be important for either small (probably 1D) problems or for parallel simulations run on many processors. Second, one may consistently solving the equations to some low order using faster, simpler algorithms (replacing, for example, the usual RK4). The latter is particularly attractive, although in practice it may be desirable to retain higher order methods when integrating along z. We investigate some of the possibilities.

MOPSO51	Feasibility of an XUV FEL Oscillator at ASTA	88
	A.H. Lumpkin Fermilab, Batavia, USA H. Freund LANL, Los Alamos, New Mexico, USA M.W. Reinsch LBNL, Berkeley, California, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. A significant opportunity exists at the Advanced Superconducting Test Accelerator (ASTA) facility presently under construction at Fermilab to enable the first XUV free electron laser (FEL) oscillator experiments. The ultrabright beam from the L-band photoinjector will provide sufficient gain to compensate for reduced mirror reflectances in the VUV-XUV regimes, the 3-MHz micropulse repetition rate for 1 ms will support an oscillator configuration, the SCRF linac will provide stable energy, and the eventual GeV-scale energy with three TESLA-type cryomodules will satisfy the FEL resonance condition in the XUV regime. Concepts based on combining such beams with a 5-cm-period undulator and optical resonator cavity for an FEL oscillator are described. We used the 68% reflectances for normal incidence on multilayer metal mirrors developed at LBNL. Initial simulations using GINGER with an oscillator module and MEDUSA:OPC show saturation for the 13.4-nm case after 300 and 350 passes, respectively,of the 3000 pulses. Initially, VUV experiments could begin in the 180- to 120-nm regime using MgF2-coated Al mirrors with only one cryomodule installed and beam energies of 250-300 MeV. LBNL X-ray optics site: http://xdb.lbl.gov/Section4

MOPSO57	Measurement of Wigner Distribution Function for Beam Characterization of FELs	92
	T. Mey, K. Mann, B. Schäfer LLG, Goettingen, Germany B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke DESY, Hamburg, Germany
	Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

MOPSO59	The Influence of the Magnetic Field Inhomogeneity on the Spontaneous Radiation and the Gain in the Plane Wiggler	97
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC We calculate the spectral distribution of spontaneous emission and the gain of electrons moving in plane wiggler with inhomogeneous magnetic field. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. We average the equations of motion over fast undulator part and obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearence of additional peaks in the spectral distribution of spontaneous radiation and the gain.

MOPSO60	Channeled Positrons as a Source of Gamma Radiation	101
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC A possibility of channeling of low-energy (5 / 20Mev) relativistic positrons with coaxial symmetry around separate crystal axes of negative ions in some types of crystals, is shown. The annihilation processes of positrons with medium electrons are investigated in details. The lifetime of a positron in the regime of channeling is estimated 〖10〗^-6 sec which on a 〖10〗⁹/〖10〗⁸ times is bigger than at usual cases.

MOPSO61	Modulated Medium for Generation of Transition Radiation	105
	K.B. Oganesyan ANSL, Yerevan, Armenia
	Funding: ISTC It is shown on an example of amorphous quartz, under the influence of a standing microwave field, at its certain parameters, superlattice is created in the medium where difference in values of dielectric constants of neighboring layers can be up to third order. This superlattice exists during the nanosecond, however it is sufficient for using it as a radiator for generation of transition radiation by relativistic electrons.

MOPSO65	Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping	108
	J. Qiang, C.E. Mitchell LBNL, Berkeley, California, USA
	Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO66	Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons	112
	J. Qiang, J.N. Corlett, P. Emma, C.E. Mitchell, C. F. Papadopoulos, G. Penn, M.W. Reinsch, R.D. Ryne, M. Venturini LBNL, Berkeley, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation.

MOPSO69	Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion	117
	C.B. Schroeder, E. Esarey, W. Leemans, J. van Tilborg LBNL, Berkeley, California, USA Y. Ding, Z. Huang SLAC, Menlo Park, California, USA F.J. Grüner, A.R. Maier CFEL, Hamburg, Germany
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Laser-plasma accelerators (LPAs) compactly produce fs beams with kA peak current and low (sub-micron) transverse emittance. Presently, the energy spread (percent-level) hinders the FEL application. Slippage of the fs beam in the FEL also suppresses lasing in the soft-x-ray, and longer, wavelength regimes. Given experimentally demonstrated LPA electron beam parameters, we discuss methods of beam phase space manipulation after the LPA to achieve FEL lasing. Decompression is examined as a solution to reduce the slice energy spread and slippage effects. We present a theoretical analysis of the stretched (and chirped) LPA beam in the FEL and determine the optimal decompression. Dispersion, coupled to a transverse gradient undulator (TGU), is also considered to enable LPA-driven FELs. Using a TGU has the advantages of shorter pulse duration, smaller bandwidth, and wavelength stabilization. We present numerical modeling for SASE and seeded XUV and soft x-ray FELs driven by LPAs after beam manipulation (decompression and/or dispersion). Recent advances in LPA performance will be presented, and experimental plans to demonstrate LPA-driven FEL lasing at LBNL will be discussed.

MOPSO70	Crystal Channeling Acceleration Research for High Energy Linear Collider at ASTA Facility	122
	Y.-M. Shin Northern Illinois University, DeKalb, Illinois, USA K. Carlson, M.D. Church, V.D. Shiltsev, D.A. Still Fermilab, Batavia, USA J.C. Tobin UMD, College Park, Maryland, USA
	The density of charge carriers in solids is significantly higher than what was considered above in plasma, and correspondingly, the longitudinal fields of up to 10 TV/m are possible. It was suggested that particles are accelerated along major crystallographic directions, which provide a channeling effect in combination with low emittance determined by an Angstrom-scale aperture of the atomic “tubes.” However, the major challenge of this channeling acceleration is that ultimate acceleration gradients might require relativistic intensities at hard x-ray regime (~ 40 keV), exceeding those conceivable for x-rays as of today, though x-ray lasers can efficiently excite solid plasma and accelerate particles inside a crystal channel. However, the acceleration will take place only in a short time before full dissociation of the lattice. Carbon nanotubes have great potential with a wide range of flexibility and superior physical strength, which can be applied to channeling acceleration and possibly fast cooling. This talk will present past and current efforts on crystal acceleration research and discuss feasible experiments with the ASTA and beyond.

MOPSO73	Suface Roughness Wakefield in FEL Undulator	127
	G.V. Stupakov SLAC, Menlo Park, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL. [1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.

MOPSO74	Reevaluation of Coherent Electron Cooling Gain Factor	132
	G.V. Stupakov SLAC, Menlo Park, California, USA M.S. Zolotorev LBNL, Berkeley, California, USA
	In Ref. [1] the authors put forward a concept of coherent electron cooling of hadrons. At the core of the concept lies the following idea: a density perturbation induced by an hadron in a co-propagating relativistic electron beam is amplified by several orders of magnitude in a free electron laser (FEL). After the FEL the electron beam is merged again with the hadron one and the amplified electric field in the electron beam acts back on each hadron resulting, after many repetitions, in cooling of the hadron beam. The efficiency of the process is critically determined by the amplification factor of the longitudinal electric field induced by the hadron in the electron beam. In this work we show that this factor is actually considerably smaller than the (conventionally defined) FEL gain with the smallness parameter to be the relative bandwidth of the FEL amplifier. [1] V. N. Litvinenko and Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

MOPSO76	FEL Operation With the Superconducting RF Photo Gun at ELBE	136
	J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, R. Schurig, W. Seidel, H. Vennekate, R. Xiang HZDR, Dresden, Germany T. Kamps, J. Rudolph HZB, Berlin, Germany I. Will MBI, Berlin, Germany
	The superconducting RF photoinjector (SRF gun) operating with a 31/2-cell niobium cavity and Cs2Te photocathodes is installed at the ELBE radiation center. The gun provides beams for ELBE as well as in a separate diagnostics beam line for beam parameter measurements. Since 2012 a new UV driver laser system developed by MBI has been installed for the SRF gun . It delivers CW or bust mode pulses with 13 MHz repetition rate or with reduced rates of 500, 200, and 100 kHz at an average UV power of about 1 W. The new laser allows the gun to serve as the driver for the infrared FELs at ELBE. In the first successful experiment a 250 μA beam with 3.3 MeV from SRF gun was injected into ELBE, further accelerated in the ELBE superconducting linac modules and then guided to the U100 undulator. First lasing was achieved at the wavelength of 41 μm. The spectrum, detuning curve and further parameters were measured.

MOPSO77	Timing Jitter Measurements of the SwissFEL Test Injector	140
	C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger PSI, Villigen PSI, Switzerland C.P. Hauri EPFL, Lausanne, Switzerland
	To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

MOPSO81	Broad-band Amplifier Based on Two-stream Instability	144
	G. Wang, Y.C. Jing, V. Litvinenko BNL, Upton, Long Island, New York, USA
	A broadband FEL amplifier is of great interests for short-pulse generation in FEL technology as well as for novel hadron beam cooling technique, such as CeC. We present our founding of a broadband amplification in 1D FEL based on electron beam with two energy peaks and a strong space charge forces. We present the optimization of such amplifier and connect its origin to the two-stream instability in electron plasma. In this work, we study how the two-stream instability affects the FEL process and consider various applications in amplifying short spikes of electron current modulation.

MOPSO82	JLIFE: The Jefferson Lab Interactive Front End for the Optical Propagation Code	149
	A.M. Watson, M.D. Shinn JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC and supported by the ONR, the Joint Technology Office, and the DOE under U.S. DOE Contract No. DE-AC05-06OR23177. We present details on a graphical interface for the open source software program Optical Propagation Code, or OPC. [1] This interface, written in Java, allows a user with no knowledge of OPC to create an optical system, with lenses, mirrors, apertures, etc. and the appropriate drifts between them. The Java code creates the appropriate Perl script that serves as the input for OPC. The mode profile is then output at each optical element. The display can be either an intensity profile along the x axis, or as an isometric 3D plot which can be tilted and rotated. These profiles can be saved. Examples of the input and output will be presented. [1] J. G. Karssenberg, P. J. M. van der Slot, I. V. Volokhine, J. W. J. Verschuur, and K.-J. Boller, “Modeling paraxial wave propagation in free-electron laser oscillators”, JAP 100, 093106 (2006).

MOPSO84	Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources	152
	T. Zhang, D. Wang, G.L. Wang, H.F. Yao SINAP, Shanghai, People's Republic of China J.S. Liu, C. Wang, W.T. Wang, Z.N. Zeng Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China J.Q. Wang, S.H. Wang IHEP, Beijing, People's Republic of China
	With the stat-of-the-art laser technique, the quality of electron beam generated from laser-plasma accelerator (LPA) is now becoming much more better. The natural merits LPA beam, e.g. high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much compact X-ray light sources, e.g. table-top X-ray free-electron laser, although the radiation power is limited by the rather larger energy spread than conventional LINAC. Luckily, much more power could be extracted by using the undulator with transverse gradient (TGU) when energy spread effect could be compensated. Here we introduce a novel soft x-ray light source driven by LPA based on TGU technique. Meanwhile we present a simple idea on how to achieve much higher rep-rate (e.g. ~100 kHz) storage ring based FELs boosted by TGU.

Paper

Title

Page

Measurement of Electron-Beam and Seed Laser Properties Using an Energy Chirped Electron Beam

24

E. Allaria, G. De Ninno, S. Di Mitri, W.M. Fawley, E. Ferrari, L. Fröhlich, G. Penco, P. Sigalotti, S. Spampinati, C. Spezzani, M. Trovò
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. De Ninno, S. Spampinati
University of Nova Gorica, Nova Gorica, Slovenia
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy

We present a new method that uses CCD images of the FERMI electron beam at the dump spectrometer after the undulator to determine various electron beam and external seed laser properties. By taking advantage of the correlation between time and electron beam energy for a quasi-linearly chirped electron beam and the fact that the FERMI seed laser pulse (~180 fs) is much shorter than the electron beam duration (~1 ps), measurements of the e-beam pulse length and temporally local energy chirp and current are possible. Moreover, the scheme allows accurate determination of the timing jitter between the electron beam and the seed laser, as well as a measure of the latter's effective pulse length in the FEL undulators. The scheme can be also provide an independent measure of the energy transferred from the electron beam to the FEL output radiation. We describe the proposed method as well as some experimental results obtained at the seeded FERMI FEL.

MOPSO04

Theoretical Analysis of a Laser Undulator-Based High Gain FEL

27

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

The use of laser (or RF) undulators is nowadays considered attractive for FEL applications, particularly those that aim to utilize relatively low-energy electron beams. In the context of the standard theoretical analysis, the counter-propagating laser pulse is usually treated in the plane-wave approximation, neglecting amplitude and phase variation. In this paper, we develop a three-dimensional, analytical theory of a high-gain FEL based on a laser or RF undulator, taking into account the longitudinal variation of the undulator field amplitude, the laser Gouy phase and the effects of emittance and energy spread in the electron beam. Working in the framework of the Vlasov-Maxwell formalism, we derive a self-consistent equation for the radiation amplitude in the linear regime, which is then solved to good approximation by means of an orthogonal expansion technique [*]. Numerical results obtained from our analysis are used in the study of an example of a compact, laser undulator-based, X-ray FEL.
*P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).

MOPSO06

Paraxial Approximation in CSR Modeling Using the Discontinuous Galerkin Method

32

D. A. Bizzozero, J.A. Ellison, K.A. Heinemann, S.R. Lau
UNM, Albuquerque, New Mexico, USA

Funding: This work was primarily supported by DOE under DE-FG-99ER41104. The work of DB and SL was partially supported by NSF grant PHY 0855678 to the University of New Mexico.
We continue our study* of CSR from a bunch moving on an arbitrary curved trajectory. In that study we developed an accurate 2D CSR Vlasov-Maxwell code (VM3@A) and applied it to a four dipole chicane bunch compressor. Our starting point now is the well-established paraxial approximation** with boundary conditions for a perfectly conducting vacuum chamber with uniform cross-section. This is considerably different from our previous approach* where we calculated the fields from an integral over history, using parallel plate boundary conditions. In this study, we present a Discontinuous Galerkin (DG) method for the paraxial approximation equations. Our basic tool is a MATLAB DG code on a GPU using MATLAB's gpuArray; the code was developed by one of us (DB). We discuss our results in the context of previous work and outline future applications for DG, including a Vlasov-Maxwell study.
* See PRST-AB 12 080704 (2009) and Proceedings from ICAP2012 TUSDC2.
** See PRST-AB 7 054403 (2004), PRST-AB 12 104401 (2009) and Jpn. J. Appl. Phys. 51 016401 (2012).

MOPSO07

Channeling Radiation With Low-Energy Electron Beams: Experimental Plans and Status at Fermilab

38

B.R. Blomberg, D. Mihalcea, H. Panuganti, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
C.A. Brau, B.K. Choi, B.L. Ivanov, M.H. Mendenhall
Vanderbilt University, Nashville, TN, USA
W.E. Gabella
Vanderbilt University, W.M. Keck Foundation Free-Electron Laser Center, Nashville, USA
W.S. Wagner
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany

Funding: This work was supported by the DARPA Axis program under contract AXIS N66001-11-1-4196 with Vanderbilt University and Northern Illinois University.
Channeling radiation is an appealing radiation process to produce x-ray radiation with low-energy electron beams. In this contribution we describe the anticipated performance and preliminary results from a channeling radiation experiment to produce ~ 1.2-keV radiation from a ~ 4-MeV electron beam at Fermilab's high-brightness electron source lab(HBESL). We also discuss plans to produce X-ray radiation ([10,80]-keV photon energy) at Fermilab's advanced superconducting test accelerator (ASTA).

MOPSO08

Unaveraged Modelling of a LWFA Driven FEL

43

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

Preliminary simulations of a Laser Wakefield Field Accelerator driven FEL are presented using the 3D unaveraged, broad bandwidth FEL simulation code Puffin. The radius of the matched low emittance electron beam suggests that the FEL interaction will be strongly affected by radiation diffraction. The parameter scaling and comparison between 3D and equivalent 1D simulations appears to confirm the interaction is diffraction dominated. Nevertheless, output powers are predicted to be greater than those of similar unaveraged FEL models. Possible reasons for the discrepancies between the averaged and unaveraged simulation results are discussed.
[1] - AR Maier, A Meseck, S Reiche, CB Schroeder, T Seggebrock, and F Gruner, Phys Rev X 2, 031019 (2012)

MOPSO09

Investigation of a 2-Colour Undulator FEL Using Puffin

47

L.T. Campbell, B.W.J. MᶜNeil
USTRAT/SUPA, Glasgow, United Kingdom
S. Reiche
PSI, Villigen PSI, Switzerland

The unaveraged FEL code Puffin* is used to investigate a 2 color FEL. In the scheme under investigation, undulator modules are tuned alternately to generate 2 frequencies quasi-simultaneously, which should result in greater stability than generating them consecutively. The advantage of using Puffin is that it provides the capability of modelling a broad bandwidth spectrum. For example, radiation at 1nm and 2.4nm is difficult to model simultaneously in standard averaged FEL codes. An unaveraged code like Puffin is able to model 2 (or more) wavelengths with a much wider spacing.
* LT Campbell and BWJ McNeil, Phys. Plasmas 19, 093119 (2012)

MOPSO17

The Present Status of the Theory of the FEL-based Hadron Beam Cooling

52

A. Elizarov, V. Litvinenko
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 (CeC)* device is one of the new facilities under construction in BNL. The CeC is a realization of the stochastic cooling with an electron beam serving as a pick-up and kicker. Hadrons generate electron density perturbations in the modulator section, then these perturbations are amplified in an FEL, and then, they accelerate (or decelerate) hadrons in the kicker by electric field with respect to their velocities. Here we present the theoretical description of the modulator sector**,***, where the electron density perturbations are formed and our new results on the time evolution of these perturbations in the FEL section, where they are amplified.
* V. N. Litvinenko, Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).
** A. Elizarov, V. Litvinenko, G. Wang, IPAC'12, weppr099 (2012).
*** A. Elizarov, V. Litvinenko, IPAC'13, mopwo088 (2013).

MOPSO27

Study of CSR Effects in the Jefferson Laboratory FEL Driver

58

C.C. Hall, S. Biedron, T.A. Burleson, S.V. Milton, A.L. Morin
CSU, Fort Collins, Colorado, USA
S.V. Benson, D. Douglas, P.E. Evtushenko, F.E. Hannon, R. Li, C. Tennant, S. Zhang
JLAB, Newport News, Virginia, USA
B.E. Carlsten, J.W. Lewellen
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work also received supported under U.S. DOE Contract No. DE-AC05-06OR23177.
In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped.

MOPSO30

Simple Setups for Carrier-envelope-phase Stable Single-cycle Attosecond Pulse Generation

63

J. Hebling, G. Almási, J.A. Fülöp, M.I. Mechler, Z. Tibai, Gy. Tóth
University of Pecs, Pécs, Hungary

Funding: Work supported by Hungarian Research Fund (OTKA), grant number 101846, and from SROP-4.2.1.B-10/2/KONV-2010-0002 and SROP-4.2.2/B-10/1-2010-0029
Robust methods for producing waveform-controlled half-cycle–few-cycle pulses in the mid-infrared (MIR)–extreme ultraviolet (EUV) spectral range are proposed. They are based on coherent Thomson scattering of THz pulses on relativistic ultrathin electron layers and coherent undulator radiation of relativistic ultrathin electron layers, respectively. The ultrathin electron layers are produced by microbunching of ultrashort electron bunches by a TW power laser in a modulator undulator. According to our numerical calculations it is possible to generate as short as 10 nm long electron layers if a single-period modulator undulator with period length significantly shorter than the resonant one is used and the undulator parameter is only K=0.25. Thomson scattering of THz pulses on ultrathin electron layers with only 50 MeV energy can generate for example 170 as long single-cycle pulses at 80 nm wavelength with 0.1 nJ energy. Coherent undulator radiation of ultrathin electron layers with 450 MeV energy can generate single-cycle radiation in the 20 nm – 1000 nm wavelength range. The corresponding pulse energy and pulse duration vary in the 10 pJ – 2 nJ and 47 as – 2.1 fs ranges, respectively.

MOPSO31

Quasiperiodic Method of Averaging Applied to Planar Undulator Motion Excited by a Fixed Traveling Wave

762

K.A. Heinemann, J.A. Ellison
UNM, Albuquerque, New Mexico, USA
M. Vogt
DESY, Hamburg, Germany

Funding: The work of JAE and KH was supported by DOE under DE-FG-99ER41104. The work of MV was supported by DESY.
We present a mathematical analysis of planar motion of energetic electrons moving through a planar dipole undulator, excited by a fixed planar polarized plane wave Maxwell field in the X-Ray FEL regime.* We study the associated 6D Lorentz system as the wavelength of the traveling wave varies. The 6D system is reduced, without approximation, to a 2D system (for a scaled energy deviation and generalized ponderomotive phase) in a form for a rigorous asymptotic analysis using the Method of Averaging (MoA), a long time perturbation theory. As the wavelength varies the system passes through resonant and nonresonant (NR) zones and we develop NR and near-to-resonant (NtoR) normal form approximations. For a special initial condition, on resonance, we obtain the well-known FEL pendulum system. We prove NR and NtoR first-order averaging theorems, in a novel way, which give optimal error bounds for the approximations. The NR case is an example of quasiperiodic averaging where the small divisor problem enters in the simplest possible way. To our knowledge the analysis has not been done with the generality here nor has the standard FEL pendulum system been derived with error bounds.
* J.A. Ellison, K. Heinemann, M. Vogt, M. Gooden: arXiv:1303.5797 [physics.acc-ph]

MOPSO34

Highly Efficient, High-energy THz Pulses from Cryo-cooled Lithium Niobate for Accelerator and FEL Applications

68

K.-H. Hong, E. Granados, S.-W. Huang, W.R. Huang, F.X. Kaertner, R. Koustuban, L.E. Zapata
MIT, Cambridge, Massachusetts, USA
F.X. Kaertner
CFEL, Hamburg, Germany

Funding: This work was supported by DARPA under contract N66001-1-11-4192.
Intense, ultrafast THz fields are of great interest for electron acceleration, beam manipulation and measurement, and pump-probe experiments with coherent soft/hard x-ray sources based on FELs or inverse Compton scattering sources. Acceleration at THz frequencies has an advantage over RF in terms of accessing high electric-field gradients (>100 MV/cm), while the beam delivery can be treated quasi-optically. However, high-field THz pulse generation is still demanding when compared with conventional RF generation. In this paper, we present highly efficient, single-cycle, 0.45 THz pulse generation by optical rectification of 1.03 μm pulses in cryogenically cooled lithium niobate (LN). Using a near-optimal duration of 680 fs and a pump energy of 1.2 mJ, we report conversion efficiencies above 3% [1], >10 times higher than previous report (0.24%) [2]. Cryogenic cooling of lithium niobate significantly reduces the THz absorption, which will enable the scaling of THz pulse energies to the mJ. We will also report on polarization and mode conversion using segmented THz waveplates to generate radially-polarized TEM01 modes, suitable for THz electron acceleration in dielectric waveguide.
[1] S.-W. Huang et al., Opt. Lett. 38, 796-798 (2013).
[2] J. A. Fülöp et al., Opt. Lett. 37, 557-559 (2012).

MOPSO40

CLARA Accelerator Design and Simulations

72

P.H. Williams, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, B.P.M. Liggins, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Science & Technology Facilities Council
We present the accelerator design for CLARA (Compact Linear Advanced Research Accelerator) at Daresbury Laboratory. CLARA will be a testbed for novel FEL configurations. The accelerator will consist of an RF photoinjector, S-band acceleration and transport to 250MeV including X-band linearisation and magnetic bunch compression. We describe the transport in detail. Beam dynamics simulations are then used to define a set of operating working points suitable for the different FEL schemes intended to be tested on CLARA.

MOPSO43

High Power Laser Transport System for Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns

75

J.M.D. Kowalczyk, M.R. Hadmack, J. Madey, E.B. Szarmes, M.H.E.H. Vinci
University of Hawaii, Honolulu, HI, USA

Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03.
Heat from a high power, short pulse laser deposited on the surface of a thermionic electron gun cathode will diffuse into the bulk producing a surface cooling effect that counteracts the electron back-bombardment (BB) heating intrinsic to the gun. The resulting constant temperature stabilizes the current allowing extension of the gun’s peak current and duty cycle. To enable this laser cooling, high power laser pulses must be transported to the high radiation zone of the electron gun, and their transverse profile must be converted from Gaussian to top-hat to uniformly cool the cathode. A fiber optic transport system is simple, inexpensive, and will convert a Gaussian to a top-hat profile. Coupling into the fiber efficiently and without damage is difficult as tight focusing is required at the input and, if coupled in air, the high fluence will breakdown the air resulting in lost energy. We have devised a vacuum fiber coupler (VFC) that allows the focus to occur in vacuum, avoiding the breakdown of air, and have successfully transported 10 ns long, 85 mJ pulses from a 1064 nm Nd:YAG laser through 20 m of 1 mm diameter fiber enabling testing of the laser cooling concept.

MOPSO44

Laser Cooling to Counteract Back-Bombardment Heating in Microwave Thermionic Electron Guns

79

J.M.D. Kowalczyk, M.R. Hadmack, J. Madey
University of Hawaii, Honolulu, HI, USA

Funding: This work was funded by the Department of Homeland Security through grant #2011-DN-077-ARI055-03.
A theoretical study of the use of laser cooling to counteract electron back-bombardment heating (BB) in thermionic electron guns is presented. Electron beams with short bunches, minimum energy spread, and maximum length pulse trains are required for many applications, including the inverse-Compton X-ray source being developed at UH. Currently, these three electron beam parameters are limited by BB which causes the cathode temperature and emission current to increase leading to beam loading. Beam loading elongates the bunches by shifting the electrons’ relative phases, introduces energy spread by reducing the energy of electrons emitted later in the macropulse, and forces the use of shorter macropulses to minimize energy spread. Irradiation of the electron gun cathode with a short laser pulse prior to beam acceleration allows the laser heat to diffuse into the cathode bulk effectively cooling the surface and counteracting the BB. Calculation of the the cooling produced by laser pulses of various duration and energy is presented.

MOPSO49

Numerical Accuracy When Solving the FEL Equations

82

R.R. Lindberg
ANL, Argonne, USA

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The usual method of numerically solving the FEL equations involves dividing both the e-beam and radiation field into "slices" that are loaded one at a time into memory. This scheme is only first order accurate in the discretization of the ponderomotive phase because having only one slice in memory effectively results in a first order interpolation of the field-particle coupling. While experience has shown that FEL simulations work quite well, the first order accuracy opens the door to two possible ways of speeding up simulation time. First, one can consider higher order algorithms; unfortunately, these methods appear to require all the particle and field data in memory at the same time, and therefore will typically only be important for either small (probably 1D) problems or for parallel simulations run on many processors. Second, one may consistently solving the equations to some low order using faster, simpler algorithms (replacing, for example, the usual RK4). The latter is particularly attractive, although in practice it may be desirable to retain higher order methods when integrating along z. We investigate some of the possibilities.

MOPSO51

Feasibility of an XUV FEL Oscillator at ASTA

88

A.H. Lumpkin
Fermilab, Batavia, USA
H. Freund
LANL, Los Alamos, New Mexico, USA
M.W. Reinsch
LBNL, Berkeley, California, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A significant opportunity exists at the Advanced Superconducting Test Accelerator (ASTA) facility presently under construction at Fermilab to enable the first XUV free electron laser (FEL) oscillator experiments. The ultrabright beam from the L-band photoinjector will provide sufficient gain to compensate for reduced mirror reflectances in the VUV-XUV regimes, the 3-MHz micropulse repetition rate for 1 ms will support an oscillator configuration, the SCRF linac will provide stable energy, and the eventual GeV-scale energy with three TESLA-type cryomodules will satisfy the FEL resonance condition in the XUV regime. Concepts based on combining such beams with a 5-cm-period undulator and optical resonator cavity for an FEL oscillator are described. We used the 68% reflectances for normal incidence on multilayer metal mirrors developed at LBNL*. Initial simulations using GINGER with an oscillator module and MEDUSA:OPC show saturation for the 13.4-nm case after 300 and 350 passes, respectively,of the 3000 pulses. Initially, VUV experiments could begin in the 180- to 120-nm regime using MgF2-coated Al mirrors with only one cryomodule installed and beam energies of 250-300 MeV.
*LBNL X-ray optics site: http://xdb.lbl.gov/Section4

MOPSO57

Measurement of Wigner Distribution Function for Beam Characterization of FELs

92

T. Mey, K. Mann, B. Schäfer
LLG, Goettingen, Germany
B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke
DESY, Hamburg, Germany

Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

MOPSO59

The Influence of the Magnetic Field Inhomogeneity on the Spontaneous Radiation and the Gain in the Plane Wiggler

97

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
We calculate the spectral distribution of spontaneous emission and the gain of electrons moving in plane wiggler with inhomogeneous magnetic field. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. We average the equations of motion over fast undulator part and obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearence of additional peaks in the spectral distribution of spontaneous radiation and the gain.

MOPSO60

Channeled Positrons as a Source of Gamma Radiation

101

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
A possibility of channeling of low-energy (5 / 20Mev) relativistic positrons with coaxial symmetry around separate crystal axes of negative ions in some types of crystals, is shown. The annihilation processes of positrons with medium electrons are investigated in details. The lifetime of a positron in the regime of channeling is estimated 〖10〗^-6 sec which on a 〖10〗⁹/〖10〗⁸ times is bigger than at usual cases.

MOPSO61

Modulated Medium for Generation of Transition Radiation

105

K.B. Oganesyan
ANSL, Yerevan, Armenia

Funding: ISTC
It is shown on an example of amorphous quartz, under the influence of a standing microwave field, at its certain parameters, superlattice is created in the medium where difference in values of dielectric constants of neighboring layers can be up to third order. This superlattice exists during the nanosecond, however it is sufficient for using it as a radiator for generation of transition radiation by relativistic electrons.

MOPSO65

Suppression of Wakefield Induced Energy Spread Inside an Undulator Through Current Shaping

108

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

Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Wakefields from resistive wall and surface roughness inside an undulatory can cause significant growth of beam energy spread and limit the performance of x-ray FEL radiation. In this paper, we propose a method to mitigate such energy modulation by appropriately conditioning the electron beam current profile. Numerical example and potential applications will also be discussed.

MOPSO66

Start-to-end Simulation of a Next Generation Light Source Using the Real Number of Electrons

112

J. Qiang, J.N. Corlett, P. Emma, C.E. Mitchell, C. F. Papadopoulos, G. Penn, M.W. Reinsch, R.D. Ryne, M. Venturini
LBNL, Berkeley, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Funding: This research was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Start-to-end simulation plays an important role in design and optimization of next generation light sources. In this paper, we will present start-to-end (from the photocathode to the end of undulator) simulations of a high repetition rate FEL-based Next Generation Light Source driven by CW superconducting linac with the real number of electrons (~2 billion electrons/bunch) using the multi-physics parallel beam dynamics code IMPACT. We will discuss challenges, numerical methods and physical models used in the simulation. We will also present simulation results of a beam transporting through photoinjector, beam delivery system, and final X-ray FEL radiation.

MOPSO69

Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion

117

C.B. Schroeder, E. Esarey, W. Leemans, J. van Tilborg
LBNL, Berkeley, California, USA
Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA
F.J. Grüner, A.R. Maier
CFEL, Hamburg, Germany

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Laser-plasma accelerators (LPAs) compactly produce fs beams with kA peak current and low (sub-micron) transverse emittance. Presently, the energy spread (percent-level) hinders the FEL application. Slippage of the fs beam in the FEL also suppresses lasing in the soft-x-ray, and longer, wavelength regimes. Given experimentally demonstrated LPA electron beam parameters, we discuss methods of beam phase space manipulation after the LPA to achieve FEL lasing. Decompression is examined as a solution to reduce the slice energy spread and slippage effects. We present a theoretical analysis of the stretched (and chirped) LPA beam in the FEL and determine the optimal decompression. Dispersion, coupled to a transverse gradient undulator (TGU), is also considered to enable LPA-driven FELs. Using a TGU has the advantages of shorter pulse duration, smaller bandwidth, and wavelength stabilization. We present numerical modeling for SASE and seeded XUV and soft x-ray FELs driven by LPAs after beam manipulation (decompression and/or dispersion). Recent advances in LPA performance will be presented, and experimental plans to demonstrate LPA-driven FEL lasing at LBNL will be discussed.

MOPSO70

Crystal Channeling Acceleration Research for High Energy Linear Collider at ASTA Facility

122

Y.-M. Shin
Northern Illinois University, DeKalb, Illinois, USA
K. Carlson, M.D. Church, V.D. Shiltsev, D.A. Still
Fermilab, Batavia, USA
J.C. Tobin
UMD, College Park, Maryland, USA

The density of charge carriers in solids is significantly higher than what was considered above in plasma, and correspondingly, the longitudinal fields of up to 10 TV/m are possible. It was suggested that particles are accelerated along major crystallographic directions, which provide a channeling effect in combination with low emittance determined by an Angstrom-scale aperture of the atomic “tubes.” However, the major challenge of this channeling acceleration is that ultimate acceleration gradients might require relativistic intensities at hard x-ray regime (~ 40 keV), exceeding those conceivable for x-rays as of today, though x-ray lasers can efficiently excite solid plasma and accelerate particles inside a crystal channel. However, the acceleration will take place only in a short time before full dissociation of the lattice. Carbon nanotubes have great potential with a wide range of flexibility and superior physical strength, which can be applied to channeling acceleration and possibly fast cooling. This talk will present past and current efforts on crystal acceleration research and discuss feasible experiments with the ASTA and beyond.

MOPSO73

Suface Roughness Wakefield in FEL Undulator

127

G.V. Stupakov
SLAC, Menlo Park, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Among several wakefield models for the FEL undulator vacuum chamber a simple sinusoidal wall modulation with a small ratio of height to wavelength is especially attractive because of its simplicity [1]. The model neglects a so called resonant mode wakefield and has an (integrable) singularity at the origin which makes difficult its use in practical simulations. In this work we generalize the longitudinal wake of a sinusoidally modulated wall to include the effect of the resonant mode. This also removes the singularity of the wake at the origin. The new wake is used to evaluate the roughness wakefield effect in the undulator of SwissFEL.
[1] G. Stupakov, in "Nonlinear and Collective Phenomena in Beam Physics 1998" Workshop, New York (1999), no. 468 in AIP Conference Proceedings, pp. 334–47.

MOPSO74

Reevaluation of Coherent Electron Cooling Gain Factor

132

G.V. Stupakov
SLAC, Menlo Park, California, USA
M.S. Zolotorev
LBNL, Berkeley, California, USA

In Ref. [1] the authors put forward a concept of coherent electron cooling of hadrons. At the core of the concept lies the following idea: a density perturbation induced by an hadron in a co-propagating relativistic electron beam is amplified by several orders of magnitude in a free electron laser (FEL). After the FEL the electron beam is merged again with the hadron one and the amplified electric field in the electron beam acts back on each hadron resulting, after many repetitions, in cooling of the hadron beam. The efficiency of the process is critically determined by the amplification factor of the longitudinal electric field induced by the hadron in the electron beam. In this work we show that this factor is actually considerably smaller than the (conventionally defined) FEL gain with the smallness parameter to be the relative bandwidth of the FEL amplifier.
[1] V. N. Litvinenko and Y. S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).

MOPSO76

FEL Operation With the Superconducting RF Photo Gun at ELBE

136

J. Teichert, A. Arnold, H. Büttig, M. Justus, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, R. Schurig, W. Seidel, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
T. Kamps, J. Rudolph
HZB, Berlin, Germany
I. Will
MBI, Berlin, Germany

The superconducting RF photoinjector (SRF gun) operating with a 31/2-cell niobium cavity and Cs2Te photocathodes is installed at the ELBE radiation center. The gun provides beams for ELBE as well as in a separate diagnostics beam line for beam parameter measurements. Since 2012 a new UV driver laser system developed by MBI has been installed for the SRF gun . It delivers CW or bust mode pulses with 13 MHz repetition rate or with reduced rates of 500, 200, and 100 kHz at an average UV power of about 1 W. The new laser allows the gun to serve as the driver for the infrared FELs at ELBE. In the first successful experiment a 250 μA beam with 3.3 MeV from SRF gun was injected into ELBE, further accelerated in the ELBE superconducting linac modules and then guided to the U100 undulator. First lasing was achieved at the wavelength of 41 μm. The spectrum, detuning curve and further parameters were measured.

MOPSO77

Timing Jitter Measurements of the SwissFEL Test Injector

140

C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

MOPSO81

Broad-band Amplifier Based on Two-stream Instability

144

G. Wang, Y.C. Jing, V. Litvinenko
BNL, Upton, Long Island, New York, USA

A broadband FEL amplifier is of great interests for short-pulse generation in FEL technology as well as for novel hadron beam cooling technique, such as CeC. We present our founding of a broadband amplification in 1D FEL based on electron beam with two energy peaks and a strong space charge forces. We present the optimization of such amplifier and connect its origin to the two-stream instability in electron plasma. In this work, we study how the two-stream instability affects the FEL process and consider various applications in amplifying short spikes of electron current modulation.

MOPSO82

JLIFE: The Jefferson Lab Interactive Front End for the Optical Propagation Code

149

A.M. Watson, M.D. Shinn
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC and supported by the ONR, the Joint Technology Office, and the DOE under U.S. DOE Contract No. DE-AC05-06OR23177.
We present details on a graphical interface for the open source software program Optical Propagation Code, or OPC. [1] This interface, written in Java, allows a user with no knowledge of OPC to create an optical system, with lenses, mirrors, apertures, etc. and the appropriate drifts between them. The Java code creates the appropriate Perl script that serves as the input for OPC. The mode profile is then output at each optical element. The display can be either an intensity profile along the x axis, or as an isometric 3D plot which can be tilted and rotated. These profiles can be saved. Examples of the input and output will be presented.
[1] J. G. Karssenberg, P. J. M. van der Slot, I. V. Volokhine, J. W. J. Verschuur, and K.-J. Boller, “Modeling paraxial wave propagation in free-electron laser oscillators”, JAP 100, 093106 (2006).

MOPSO84

Numerical Investigations of Transverse Gradient Undulator Based Novel Light Sources

152

T. Zhang, D. Wang, G.L. Wang, H.F. Yao
SINAP, Shanghai, People's Republic of China
J.S. Liu, C. Wang, W.T. Wang, Z.N. Zeng
Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China
J.Q. Wang, S.H. Wang
IHEP, Beijing, People's Republic of China

With the stat-of-the-art laser technique, the quality of electron beam generated from laser-plasma accelerator (LPA) is now becoming much more better. The natural merits LPA beam, e.g. high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much compact X-ray light sources, e.g. table-top X-ray free-electron laser, although the radiation power is limited by the rather larger energy spread than conventional LINAC. Luckily, much more power could be extracted by using the undulator with transverse gradient (TGU) when energy spread effect could be compensated. Here we introduce a novel soft x-ray light source driven by LPA based on TGU technique. Meanwhile we present a simple idea on how to achieve much higher rep-rate (e.g. ~100 kHz) storage ring based FELs boosted by TGU.