Novel Concepts
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.  
 
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) 		 
 
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. 		 
 
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).
 		 
 
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. 		 
 
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. 		 
 
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.  
 
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). 		 
 
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.  
 
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.  
 
WEIANO01 Towards Zeptosecond-scale Pulses From X-ray Free Electron Lasers 458
 
  • D.J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  
  The short wavelength and high peak power of the present generation of Free-Electron Lasers (FELs) opens the possibility of ultra-short pulses even surpassing the present (~10-100 attosecond) capabilities of other light sources – but only if x-ray FELs can be made to generate pulses consisting of just a few optical cycles. For hard x-ray operation (<~0.1nm), this corresponds to durations of approximately a single attosecond, and below into the zeptosecond scale. This talk will describe a proposed method [1] to generate trains of few-cycle pulses, at GW peak powers, from existing x-ray FEL facilities by using a relatively short 'afterburner'. Such pulses would enhance research opportunity in atomic dynamics and push capability towards the investigation of electronic-nuclear and nuclear dynamics. The corresponding multi-colour spectral output, with a bandwidth envelope increased by up to two orders of magnitudes over SASE, also has potential applications.
[1] D.J. Dunning, B.W.J. McNeil, N.R. Thompson, Phys. Rev. Lett. 110, 104801 (2013). 		 
slides icon Slides WEIANO01 [3.492 MB]  
 
WEOANO01 New Scheme to Generate a Multi-terawatt and Attosecond X-ray Pulse in XFELs 464
 
  • T. Tanaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  
  A new scheme to be applied in XFELs has been recently proposed*, which effectively compresses the X-ray pulse, i.e., shortens the pulse length and enhances the peak power by means of inducing a periodic current enhancement with an optical laser and applying a temporal shift between the X-ray and electron beams. In this paper, detailed mechanism of the new scheme is explained together with numerical results applied to the SACLA XFEL facility.
*T. Tanaka, PRL 110, 084801 (2013) 		 
slides icon Slides WEOANO01 [4.177 MB]  
 
WEOANO03 Longitudinal Coherence in an FEL With a Reduced Level of Shot Noise 469
 
  • V.A. Goryashko
    Private Address, Uppsala, Sweden
  • V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  
  For a planar free electron laser (FEL) configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches [1]. We calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses and the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. We also propose a scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.
V.A. Goryashko and V. Ziemann, Phys. Rev. ST Accel. Beams 16, 030702 (2013). 		 
slides icon Slides WEOANO03 [1.999 MB]  
 
WEOANO04
 Two-stream Instability at Soft X-ray Wavelengths for Increasing Brightness of Compton Sources  
 
  • N.A. Yampolsky, G.L. Delzanno, C. Huang, D.Y. Shchegolkov
    LANL, Los Alamos, New Mexico, USA
  
  Two-stream instability at soft X-ray wavelengths for increasing brightness of Compton sources. We propose a novel scheme which may result in the next generation Compton source for soft X-rays. The scheme is based on creating an electron beam distribution consisting of several energy bands and allowing for the two-stream instability to develop resulting in a short scale density modulation. The multi-stream beam distribution is created within a single bunch through EEHG mechanism which results in well separated bands with close energies. The wavelength of the microbunching caused by the two-stream instability strongly depends on the beam parameters and can be reduced down to soft X-ray wavelengths that are not achievable with other mechanisms. The microbunching can be used for  
slides icon Slides WEOANO04 [1.362 MB]