Keyword: laser
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MOOBN2 Inverse Free Electron Laser Accelerators for Driving Compact Light Sources and Detection Applications electron, undulator, acceleration, FEL 1
 
  • A.M. Tremaine, S. Boucher, A.Y. Murokh
    RadiaBeam, Santa Monica, USA
  • S.G. Anderson
    LLNL, Livermore, California, USA
  • W.J. Brown
    MIT, Cambridge, Massachusetts, USA
  • J.P. Duris, P. Musumeci, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
  • I. Pogorelsky, M.N. Polyanskiy, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
 
  Funding: Defense Threat Reduction Agency (DTRA)
Because of the broad application space for compact, 1-2 GeV accelerators, Inverse Free Electron Lasers (IFELs) are enjoying a rebirth of R&D funding. The efforts are under way in industry (RadiaBeam), academia (UCLA), and national laboratories (LLNL and BNL) to develop an ultra-compact IFEL energy booster for the photoinjector driven linear accelerating systems. The RUBICON collaboration integrates many of the institutions for proof-of-principle IFEL driven Inverse Compton Scattering (ICS) compact light source demonstrations. IFELs perform optimally in this mid-energy range, and given continual advances in laser technology, high average power IFELs with gradients well over 500 MeV/m are now feasible, leading to high quality, compact ICS and Free Electron Laser light sources. Importantly, IFEL operation can have excellent shot-to-shot energy stability, which is crucial when not only driving these light sources, but also for the downstream applications such as photofission, nuclear resonance fluorescence and standoff detection.
 
slides icon Slides MOOBN2 [2.625 MB]  
 
MOOBS1 Beam Dynamics Issues in the SNS Linac linac, ion, emittance, optics 12
 
  • A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This research is supported by UT-Battelle, LLC for the U. S. Department of Energy under contract No. DE-AC05-00OR22725
A review of the Spallation Neutron Source (SNS) linac beam dynamics is presented. It describes transverse and longitudinal beam optics, losses, activation, and comparison between the initial design and the existing accelerator. The SNS linac consists of normal conducting and superconducting parts. The peculiarities in operations with the superconducting part of the SNS linac (SCL), estimations of total losses in SCL, the possible mechanisms of these losses, and the progress in the transverse matching are discussed.
 
slides icon Slides MOOBS1 [1.270 MB]  
 
MOP010 Resonance, Particle Stability, and Acceleration in the Micro-Accelerator Platform electron, resonance, acceleration, simulation 121
 
  • J.C. McNeur, J.B. Rosenzweig, G. Travish, J. Zhou
    UCLA, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  Funding: US Defense Threat Reduction Agency
A micron-scale dielectric-based slab-symmetric accelerator is currently being designed and fabricated at UCLA. This Micro-Accelerator Platform (MAP) accelerates electrons in a 800nm wide vacuum gap via a resonant accelerating mode excited by a side-coupled optical-wavelength laser. Detailed results of particle dynamics and field simulations are presented. In particular, we examine various methods of achieving net acceleration and particle stability. Additionally, structural designs that produce accelerating fields synchronous with both relativistic and sub-relativistic electrons are discussed.
 
 
MOP014 Status and Upgrades of the NLCTA for Studies of Advanced Beam Acceleration, Dynamics, and Manipulation cavity, acceleration, radiation, electron 130
 
  • M.P. Dunning, C. Adolphsen, T.S. Chu, E.R. Colby, A. Gilevich, C. Hast, R.K. Jobe, C. Limborg-Deprey, D.J. McCormick, B.D. McKee, J. Nelson, T.O. Raubenheimer, K. Soong, G.V. Stupakov, Z.M. Szalata, D.R. Walz, F. Wang, S.P. Weathersby, M. Woodley, D. Xiang
    SLAC, Menlo Park, California, USA
 
  The Next Linear Collider Test Accelerator (NLCTA) is a low-energy electron accelerator (120 MeV) at SLAC that is used for ultra-high gradient X-band RF structure testing and advanced accelerator research. Here we give an overview of the current program at the facility, including the E-163 direct laser acceleration experiment, the echo-enabled harmonic generation (EEHG) FEL experiment, narrow-band THz generation, coherent optical transition radiation (COTR) studies, microbunching instability studies, and X-band structure testing. We also present the upgrades that are currently underway and some future programs utilizing these upgrades, including extension of the EEHG experiments to higher harmonics, and an emittance exchange experiment.  
 
MOP064 Asymmetric Laser Radiant Cooling in Storage Rings electron, photon, damping, simulation 229
 
  • E.V. Bulyak
    NSC/KIPT, Kharkov, Ukraine
  • J. Urakawa
    KEK, Ibaraki, Japan
  • F. Zimmermann
    CERN, Geneva, Switzerland
 
  Laser pulses with small spatial and temporal dimensions can interact with a fraction of the electron bunches circulating in Compton storage rings. We studied synchrotron dynamics of such bunches when laser photons scatter off from the electrons with energy higher than the synchronous energy. In this case of ‘asymmetric cooling', as shown theoretically, the stationary energy spread is much smaller than under conditions of regular scattering; the oscillations are damped faster. Coherent oscillations of large amplitude may be damped in one synchrotron period, which makes this method feasible for injection the bunches into a ring in the longitudinal phase space. The theoretical results are validated with simulations.  
 
MOP072 Design of On-Chip Power Transport and Coupling Components for a Silicon Woodpile Accelerator coupling, electron, simulation, optics 241
 
  • Z. Wu, E.R. Colby, C. McGuinness, C.-K. Ng
    SLAC, Menlo Park, California, USA
 
  Three-dimensional woodpile photonic bandgap (PBG) waveguide enables high-gradient and efficient laser driven acceleration, while various accelerator components, including laser couplers, power transmission lines, woodpile accelerating and focusing waveguides, and energy recycling resonators, can be potentially integrated on a single monolithic structure via lithographic fabrications. This paper will present designs of this on-chip accelerator based on silicon-on-insulator (SOI) waveguide. Laser power is coupled from free-space or fiber into SOI waveguide by grating structures on the silicon surface, split into multiple channels to excite individual accelerator cells, and eventually gets merged into the power recycle pathway. Design and simulation results will be presented regarding various coupling components involved in this network.  
 
MOP081 Proton Acceleration by Trapping in a Relativistic Laser Driven Uphill Plasma Snowplow plasma, proton, electron, simulation 247
 
  • A. Sahai, T.C. Katsouleas
    Duke ECE, Durham, North Carolina, USA
  • W.B. Mori, A. Tableman, J. Tonge, F.S. Tsung
    UCLA, Los Angeles, California, USA
 
  We explore a novel regime of proton and ion acceleration off of overdense Plasma created by a Laser pulse. In Coulomb explosion, Target Normal Sheath, Acoustic shock acceleration regimes the protons are neither high-energy nor monoenergetic enough for applications such as hadron radiation therapy, fast ignition fusion research and particle physics. This calls out for exploration of effective regimes of acceleration. The proposed Snowplow regime of acceleration uses a Snowplow of charge created by a relativistic Laser pulse at the critical density on a uphill Plasma density gradient. The relativistically moving Snowplow's space charge drags the protons and its velocity can be controlled to effectively trap the protons using laser pulse shape and the uphill density profile. We describe the principles behind this mechanism. We derive analytical expressions for the Snowplow velocity and its dependence on the parameter space. We primarily explore the density gradient and laser pulse shape to optimally accelerate protons from rest to the desired velocities. Preliminary, 1-D simulation results are presented and analyzed.  
 
MOP082 Modeling a 10 GeV Laser-Plasma Accelerator with INF&RNO plasma, simulation, injection, electron 250
 
  • C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The numerical modeling code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde, pronounced "inferno") is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a particle-in-cell (PIC) or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged ponderomotive force. These and other features allow for a significant speedup compared to standard full PIC simulations while still retaining physical fidelity. A boosted Lorentz frame (BLF) modeling capability has been introduced within the fluid framework enhancing the performance of the code. An example of a 10 GeV laser-plasma accelerator modeled using INF&RNO in the BLF is presented.
 
 
MOP083 Plasma Wake Excitation by Lasers or Particle Beams plasma, electron, focusing, acceleration 253
 
  • C.B. Schroeder, C. Benedetti, E. Esarey, C.G.R. Geddes, W. Leemans, C. Tóth
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed.
 
 
MOP084 A High Repetition Plasma Mirror for Staged Electron Acceleration plasma, acceleration, electron, coupling 256
 
  • T. Sokollik, E.S. Evans, A.J. Gonsalves, W. Leemans, C. Lin, K. Nakamura, J. Osterhoff, S. Shiraishi, C. Tóth, J. van Tilborg
    LBNL, Berkeley, California, USA
 
  Funding: Acknowledgment: This work is supported by the National Science Foundation and DTRA.
In order to build a compact, staged laser plasma accelerator the in-coupling of the laser beam to the different stages represents one of the key issues. To limit the spatial foot print and thus to realize a high overall acceleration gradient, a concept has to be found which realizes this in-coupling within a few centimeters. We present experiments on a tape-drive based plasma mirror which could be used to reflect the focused laser beam into the acceleration stage.
References:
* W. Leemans et. al, Phys. Today, 62, 44 (2009)
** G. Doumy et. al, Phys. Rev. E 69, 026402 (2004)
*** B. Dromey et. al,, Rev. Sci. Instrum. 75, 645 (2004)
 
 
MOP086 Fabrication of a Prototype Micro-Accelerator Platform electron, vacuum, coupling, simulation 259
 
  • J. Zhou, J.C. McNeur, G. Travish
    UCLA, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  Funding: Work supported by U.S. Defense Threat Reduction Agency, Grant no. HDTRA1-09-1-0043.
The Micro-Accelerator Platform is a laser powered particle acceleration device made from dielectric materials. Its main building blocks, distributed Bragg reflectors and nanoscale coupling slots are fabricated using cutting-edge nanofabrication techniques. In this report, a prototype device will be presented, and technical details with fabrication will be discussed. Optical property of the DBR films is measured by ellipsometry, and film surface roughness is measured using profilometer. In addition, a few remaining challenges with manufacture of this device will be discussed.
 
 
MOP087 A Laser-Driven Linear Collider: Sample Machine Parameters and Configuration emittance, focusing, collider, linear-collider 262
 
  • E.R. Colby, R.J. England, R.J. Noble
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by Department of Energy contracts DE-AC03-76SF00515 (SLAC) and DE-FG03-97ER41043-III (LEAP).
We present a design concept for an e+ e- linear collider based on laser-driven dielectric accelerator structures, and discuss technical issues that must be addressed to realize such a concept. With a pulse structure that is quasi-CW, dielectric laser accelerators potentially offer reduced beamstrahlung and pair production, reduced event pileup, and much cleaner environment for high energy physics and. For multi-TeV colliders, these advantages become significant.
 
 
MOP094 Development of Advanced Beam Halo Diagnostics at the Jefferson Lab Free-Electron-Laser Facility electron, FEL, radiation, monitoring 274
 
  • S. Zhang, S.V. Benson, D. Douglas, F.G. Wilson
    JLAB, Newport News, Virginia, USA
  • R.B. Fiorito, A.G. Shkvarunets, H.D. Zhang
    UMD, College Park, Maryland, USA
 
  Funding: Many colleagues at JLab FEL provided help with the installation of the present experimental setup. This work is partially supported by DOE Contract DE-AC05-060R23171.
High average current and high brightness electron beams are needed for many applications. At the Jefferson Lab FEL facility, the search for dark matter with the FEL laser beam has produced interesting results*, and a second very promising method for dark matter search using JLab Energy-recovery-linac (ERL) machine has been put forward**. Although the required beam current has been achieved on this machine, one key challenge is the management of beam halo. UMD has demonstrated a high dynamic range halo measurement method using a digital micro-mirror array device. A similar system has been established at JLab FEL facility as a joint effort by UMD and JLab to measure the beam halo on the high current ERL machine***. The experiment and characterization are being performed while the new UV FEL is running for optimization. In this paper, the limitations of the current system will be analyzed and study of other approaches (such as an optimized coronagraph) for further extending measuring dynamic range will be presented. In particular, we will discuss in detail the possibility of performing both longitudinal and transverse (3D) halo measurement altogether on one single system.
* A. Afanasev, et al., PRL. 101 120401 (2008).
** J. Thale, Searching for a New Gauge Boson at JLab, Newport News, VA, September 20-21, 2010
*** H. Zhang, et al., this conference.
 
 
MOP095 Experimental Determination of Damage Threshold Characteristics of IR Compatible Optical Materials electron, site, photon, accelerating-gradient 277
 
  • K. Soong, E.R. Colby, C. McGuinness
    SLAC, Menlo Park, California, USA
  • R.L. Byer, E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: Work funded by DOE contract DE‐AC02‐76SF00515 (SLAC)
The accelerating gradient in a laser-driven dielectric accelerating structure is often limited by the laser damage threshold of the structure. For a given laser-driven dielectric accelerator design, we can maximize the accelerating gradient by choosing the best combination of the accelerator’s constituent material and operating wavelength. We present here a model of the damage mechanism from ultrafast infrared pulses and compare that model with experimental measurements of the damage threshold of bulk silicon. Additionally, we present experimental measurements of a variety of candidate materials, thin films, and nanofabricated accelerating structures.
 
 
MOP096 Fabrication and Measurement of Dual Layer Silica Grating Structures for Direct Laser Acceleration acceleration, alignment, simulation, vacuum 280
 
  • E.A. Peralta, R.L. Byer
    Stanford University, Stanford, California, USA
  • E.R. Colby, R.J. England, C. McGuinness, K. Soong
    SLAC, Menlo Park, California, USA
 
  Funding: Department of Energy: DE-AC02-76SF00515(SLAC),DE-FG06-97ER41276
We present our progress in the fabrication and measurement of a transmission-based dielectric double-grating accelerator structure. The structure lends itself to simpler coupling to the accelerating mode in the waveguide with negligible group velocity dispersion effects, allowing for operation with ultra-short (fs) laser pulses. This document describes work being done at the Stanford Nanofabrication Facility to create a monolithic guided-wave structure with 800 nm period gratings separated by a fixed sub-wavelength gap using standard optical lithographic techniques on a fused silica substrate. An SEM and other characterization tools were used to measure the fabrication deviations of the grating geometry and simulations were carried out in MATLAB and HFSS to study the effects of such deviations on the resulting accelerating gradient.
 
 
MOP097 Modeling of Quasi-Phase Matching for Laser Electron Acceleration plasma, electron, simulation, acceleration 283
 
  • M.W. Lin
    The Pennsylvania State University, University Park, Pennsylvania, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
 
  Funding: This work is supported by the Defense Threat Reduction Agency through contract HDTRA1-10-1-0034.
Sensing of shielded fissile materials at long range is critically dependent on the development of compact particle accelerators. Direct laser acceleration (DLA) of electrons has the potential to meet this requirement. In DLA, the axial component of the electric field of a focused radially polarized laser pulse accelerates particles. The acceleration gradient could be estimated as 77 MeV/mm for 800 nm laser with power of 0.5 TW and 8.5 μm guided mode radius. The implementation of long guided propagation of laser pulses and the phase matching between electrons and laser pulses may limit the DLA in reality. A preformed corrugated plasma waveguide could be applied to extend the laser beam propagation distance and for quasi-phase matching between laser and electron pulses for net acceleration. We perform numerical calculations to estimate the phase matching conditions for a radially polarized laser pulse propagating in a corrugated plasma waveguide. Further, the electric field distribution of a radially polarized laser pulse propagating in this waveguide is also analyzed via particle-in-cell simulations, and will be used to guide future experiments.
* P. Serafim, et al., IEEE Trans. Plasma Sci. 28, 1155 (2000).
** A.G. York, et al., Phys. Rev. Lett. 100, 195001 (2008).
 
 
MOP101 Numerical Study of Self and Controlled Injection in 3-Dimensional Laser-Driven Wakefields plasma, simulation, electron, injection 286
 
  • A.W. Davidson, R. Fenseca, C. Joshi, W. Lu, J.L. Martins, W.B. Mori, L.O. Silva
    UCLA, Los Angeles, California, USA
 
  Funding: DOE and NSF
In plasma based accelerators (LWFA and PWFA), the methods of injecting high quality electron bunches into the accelerating wakefield is of utmost importance for various applications. Understanding how injection occurs in both self and controlled scenarios is therefore important. To simplify this understanding, we start from single particle motion in an arbitrary traveling wave wakefields, an electromagnetic structure with a fixed phase velocity(e.g., wakefields driven by non-evolving drivers), and obtain the general conditions for trapping to occur. We then compare this condition with high fidelity 3D PIC simulations through advanced particle and field tracking diagnostics. Numerous numerical convergence tests were performed to ensure the correctness of the simulations. The agreement between theory and simulations helps to clarify the role played by driver evolution on injection, and a physical picture of injection first proposed in * is confirmed through simulations. Several ideas, including ionization assisted injection, for achieving high quality controlled injection were also explored and some simulation results relevant to current and future experiments will be presented.
*W. Lu et al., PRSTAB 10, 061301, 2007
 
 
MOP102 High-Gradient High-Energy-Gain Inverse Free Electron Laser Experiment using a Helical Undulator undulator, electron, simulation, radiation 289
 
  • J.P. Duris, R.K. Li, P. Musumeci, E.W. Threlkeld, M.T. Westfall
    UCLA, Los Angeles, California, USA
 
  Funding: UC Lab fee award 09-LR-04-117055-MUSP DOE-HEP grant DE-FG02-92ER40693 Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0073
Preparations for a high energy gain inverse free electron laser (IFEL) experiment using an undulator and Brookhaven National Lab’s (BNL) Accelerator Test Facility’s (ATF) terawatt CO2 laser are underway. 3D simulations suggest that the experiment will likely accelerate a 50 MeV beam to 117 MeV in 54 cm while maintaining a low energy spread. The helical undulator is currently under construction at UCLA’s Particle Beam Physics Laboratory.
 
 
MOP104 Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure focusing, simulation, multipole, alignment 292
 
  • K. Soong, E.R. Colby
    SLAC, Menlo Park, California, USA
  • R.L. Byer, E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: Work funded by DOE contract DE‐AC02‐76SF00515 (SLAC)
A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator.
 
 
MOP113 High Quality Electron Beams Generated in a Laser Wakefield Accelerator electron, plasma, emittance, wakefield 307
 
  • W.A. Gillespie
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • M.P. Anania, C. Aniculaesei, E. Brunetti, S. Cipiccia, B. Ersfeld, M.R. Islam, R.C. Issac, D.A. Jaroszynski, G.G. Manahan, R.P. Shanks, G.H. Welsh, S.M. Wiggins
    USTRAT/SUPA, Glasgow, United Kingdom
  • S.P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A. MacLeod
    UAD, Dundee, United Kingdom
 
  Funding: The U.K. EPSRC, the EC's Seventh Framework Programme (LASERLAB-EUROPE / LAPTECH, grant agreement no. 228334) and the Extreme Light Infrastructure (ELI) project.
The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laser-plasma accelerators for the production of ultra-short electron beams as drivers of incoherent and coherent radiation sources from plasma and magnetic undulators. Here we report on the latest laser wakefield accelerator experiments on the University of Strathclyde ALPHA-X accelerator beam line looking at narrow energy spread electron beams. ALPHA-X uses a 26 TW Ti:sapphire laser (energy 900 mJ, duration 35 fs) focused into a helium gas jet (nozzle length 2 mm) to generate high quality monoenergetic electron beams with central energy in the range 80-180 MeV. The beam is fully characterised in terms of the charge, transverse emittance, energy spread and bunch length. In particular, the energy spectrum (with less than 1% measured energy spread) is obtained using a high resolution magnetic dipole imaging spectrometer.
 
 
MOP123 Colliding Pulse Injection Control in a Laser-Plasma Accelerator plasma, injection, collider, controls 325
 
  • C.G.R. Geddes, M. Chen, E. Esarey, W. Leemans, N.H. Matlis, D.E. Mittelberger, K. Nakamura, G.R.D. Plateau, C.B. Schroeder, C. Tóth
    LBNL, Berkeley, California, USA
  • D.L. Bruhwiler, J.R. Cary, E. Cormier-Michel, B.M. Cowan
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, NA-22, and in part by the Office of Science under Contract No. DE-AC02-05CH11231.
Control of injection into a high gradient laser-plasma accelerator is presented using the beat between two ’colliding’ laser pulses to kick electrons into the plasma wake accelerating phase. Stable intersection and performance over hours of operation were obtained using active pointing control. Dependence of injector performance on laser and plasma parameters were characterized in coordination with simulations. By scanning the intersection point of the lasers, the injection position was controlled, mapping the acceleration length. Laser modifications to extend acceleration length are discussed towards production of tunable stable electron bunches as needed for applications including Thomson gamma sources and high energy colliders.
 
 
MOP124 Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations plasma, electron, alignment, betatron 328
 
  • A.J. Gonsalves, C.G.R. Geddes, C. Lin, K. Nakamura, J. Osterhoff, C.B. Schroeder, S. Shiraishi, T. Sokollik, C. Tóth
    LBNL, Berkeley, California, USA
  • E. Esarey
    University of Nevada, Reno, Reno, Nevada, USA
  • W. Leemans
    UCB, Berkeley, California, USA
 
  Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy pro- vided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.
 
 
MOP127 The LLNL/UCLA High Gradient Inverse Free Electron Laser Accelerator electron, undulator, simulation, acceleration 331
 
  • S.G. Anderson, G.G. Anderson, M. Betts, S.E. Fisher, D.J. Gibson, S.S.Q. Wu
    LLNL, Livermore, California, USA
  • J.T. Moody, P. Musumeci, A.M. Tremaine
    UCLA, Los Angeles, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We describe the Inverse Free Electron Laser (IFEL) accelerator currently under construction at LLNL in collaboration with UCLA. This project combines a strongly tapered undulator with a 10 Hz repetition rate, Ti:Sapphire laser to produce > 200 MeV/m average accelerating gradient over the 50 cm long undulator. The project goal is to demonstrate IFEL accelerator technology that preserves the input beam quality and is well suited for future light source applications. We discuss the accelerator design focusing on issues associated with the use of 800 nm, 100 fs laser pulses. Three-dimensional simulations of the IFEL interaction are presented which guide the choice of laser and electron beam parameters. Finally, experimental plans and potential future developments are discussed.
 
 
MOP128 An Optimized X-band Photoinjector Design for the LLNL MEGa-Ray Project emittance, gun, electron, simulation 334
 
  • S.G. Anderson, F. Albert, C.P.J. Barty, G.A. Deis, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck, R.A. Marsh
    LLNL, Livermore, California, USA
  • C. Adolphsen, A.E. Candel, E.N. Jongewaard, Z. Li, C. Limborg-Deprey, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang, F. Zhou
    SLAC, Menlo Park, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
We present an optimized 5 + ½ cell, X-band photoinjector designed to produce 7 MeV, 250 pC, sub-micron emittance electron bunches for the LLNL Mono-Energetic Gamma-Ray (MEGa-Ray) light source. This LLNL/SLAC collaboration modifies a design previously demonstrated to sustain 200 MV/m on-axis accelerating fields*. We discuss the photoinjector operating point, optimized by scaling beam dynamics from S-band photo-guns and by evaluation of the MEGa-Ray source requirements. The RF structure design is presented along with the current status of the photoinjector construction and testing.
*A.E. Vlieks, et al., High Energy Density and High Power RF: 6th Workshop, AIP, CP691, p. 358 (2003).
 
 
MOP133 Fabrication and Measurements of a Silicon Woodpile Accelerator Structure simulation, lattice, impedance, electron 343
 
  • C. McGuinness, E.R. Colby, R.J. England, R. Laouar, R.J. Noble, K. Soong, J.E. Spencer, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
  • R.L. Byer, E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: DOE grants: DE-AC02-76SF00515 and DE-FG03-97ER41043-II
We present results for the fabrication of a silicon woodpile accelerator structure. The structure was designed to have an accelerating mode at 3.95 μm, with a high characteristic impedance and an accelerating gradient of 530 MeV/m. The fabrication process uses standard nanofabrication techniques in a layer-by-layer process to produce a three-dimensional photonic crystal with 400 nm features. Reflection spectroscopy measurements reveal a peak spanning from three to five microns, and are show good agreement with simulations.
* Sears, PRST-AB, 11, 101301, (2008).
** Cowan, PRST-AB, 11, 011301, (2008).
*** McGuinness, J. Mod. Opt., vol. 56, is. 18, pp. 2142, (2009).
**** Lin, Nature, 394, pp. 251 (1998).
 
 
MOP136 Coupler Studies for PBG Fiber Accelerators coupling, simulation, radiation, lattice 346
 
  • J.E. Spencer, R.J. England, C.-K. Ng, R.J. Noble, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
 
  Funding: U.S. Dept. of Energy contract DE-AC02-76SF00515
Photonic band gap (PBG) fibers with hollow core defects are being designed and fabricated for use as laser driven accelerators because they appear capable of providing gradients of several GeV/m at picosecond pulse lengths. While we expect to have fiber down to 1.5-2.0 micron wavelengths we still lack a viable means for efficient coupling of laser power into these structures. The reasons for this include the very different character of these TM-like modes from those familiar in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our coupling work in terms of what has been done and the options we are pursuing for both end and side coupling. In both basic coupler types, the symmetry of the PBG crystal leads to significant differences between this and the telecom field. We show that side coupling provides more possibilities and is preferred. Our motivation is to test new fiber for gradient, mode content and throughput on the NLCTA at SLAC.
 
 
MOP137 Predictive Design and Interpretation of Colliding Pulse Injected Laser Wakefield Experiments plasma, electron, simulation, emittance 349
 
  • E. Cormier-Michel, D.L. Bruhwiler, B.M. Cowan, V.H. Ranjibar
    Tech-X, Boulder, Colorado, USA
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by DOE, NA-22, and Office of Science, HEP via the SciDAC-2 project ComPASS, grant No DE-FC02-07ER41499. Resources of NERSC were used (DOE contract No DE-AC02-05CH11231).
The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtain reproducible and tunable electron bunches with low energy spread and emittance. We present recent particle-in-cell simulations of colliding pulse injection for parameters relevant to ongoing experiments at LBNL. We perform parameter scans in order to determine the best conditions for the production of high quality electron bunches, and compare the results with experimental data. We also evaluate the effect of laser focusing in the plasma channel and of higher order laser mode components on the bunch properties.
 
 
MOP141 Design, Fabrication and Characterization of a Micron-scale Electron Source Based on Field Enhanced Pyroelectric Crystals electron, simulation, diagnostics, polarization 352
 
  • H. Badakov, J.M. Allen, N.S. Carranza, G. Travish, J. Zhou
    UCLA, Los Angeles, California, USA
  • E.R. Arab
    PBPL, Los Angeles, USA
  • R.B. Yoder
    Manhattanville College, Purchase, New York, USA
 
  As a part of the Micro-Accelerator Platform (MAP) project, an electron source with a sub-micron size emitter is required. It is also desired that the source produces electrons with energies above the structure's minimum capture energy (about 25 keV) without the use of an external power supply. Field enhanced emission backed by field generation in pyroelectric crystals has been explored for this application. Here we present experimental progress towards characterization of electron, and x-ray emission. Purpose built diagnostics and specialized test assembly for optimized heat transmission are discussed.  
 
MOP142 Development of Picosecond CO2 Laser Driver for an MeV Ion Source ion, proton, plasma, ion-source 355
 
  • S. Tochitsky, D.J. Haberberger, C. Joshi
    UCLA, Los Angeles, California, USA
 
  Funding: This work is supported by DOE grant DE-FG02-92ER40727.
Laser-Driven Ion Acceleration in thin foils has demonstrated high-charge, low-emittance MeV ion beams with a picosecond duration. Such high-brightness beams are very attractive for a compact ion source or an injector for RF accelerators. However in the case of foils scaling of the pulse repetition rate and improving shot-to-shot reproducibility is a serious challenge. CO2 laser-plasma interactions provide a possibility for using a debris free gas jet for target normal sheath acceleration of ions. Gas jets have the advantage of precise density control around the critical plasma density for 10 um pulses (1019 cm-3) and can be run at 1-10 Hz. The master oscillator–power amplifier CO2 laser system at the UCLA Neptune Laboratory is being upgraded to generate 1 J, 3 ps pulses at 1Hz. For this purpose, a new 8 atm CO2 module is used to amplify a 3 ps pulse to ~10 GW level. Final amplification is realized in a 1-m long TEA CO2 amplifier, for which the bandwidth necessary for 3 ps pulses is provided by the field broadening mechanism. Modeling of the pulse amplification shows that ~0.3 TW power is achievable that should be sufficient for producing 1-3 MeV H+ protons from the gas plasma.
 
 
MOP143 Enhanced Laser-Driven Ion Acceleration via Forward Raman Scattering in a Ramped Gas Target plasma, target, electron, proton 358
 
  • S. Tochitsky, D.J. Haberberger, C. Joshi, W.B. Mori, F.S. Tsung
    UCLA, Los Angeles, California, USA
 
  Funding: This work is supported by DOE grant DE-FG02-92ER40727.
CO2 laser-plasma interactions provide a unique parameter space for using a gas jet for Target Normal Sheath Acceleration (TNSA) of ions instead of a thin foil target. The generation of 1-5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density (1019 cm-3) has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma, having similar to the gas jet symmetric, linearly ramped density distribution, occurs via formation of a sheath of hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. This mechanism of an additional heating of electrons is strongly affected by nonlinear laser-plasma interactions and results in the proton energy enhancement by more than an order of magnitude in comparison with the regular ponderomotive force scaling of TNSA. Forward directed ion beams from a gaseous target can find an application as a high-brightness ion source-injector.
 
 
MOP146 Investigation of Synchro-Betatron Couplings at S-LSR betatron, coupling, synchrotron, solenoid 367
 
  • K. Jimbo
    Kyoto IAE, Kyoto, Japan
  • T. Hiromasa, M. Nakao, A. Noda, H. Souda, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
 
  Tune couplings of beam were observed at S-LSR, Kyoto University. Synchrotron oscillation in the longitudinal direction and betatron oscillation in the horizontal direction was intentionally coupled in a drift tube located at the finite dispersive section. Horizontal and vertical coupling of betatron oscillation was also observed. This fact is a good sign of 3-D couplings to achieve a theoretically predicted crystal beam through the resonant coupling method for transverse laser cooling.  
 
MOP153 High Efficiency Laser Ion Acceleration in Low Density Plasmas proton, acceleration, plasma, simulation 376
 
  • E. d'Humières, V. Tikhonchuk
    CELIA, Talence, France
 
  Laser driven sources of high energy ions commonly use thin solid foils. A gaseous target can also produce ion beams with characteristics comparable to those obtained with solid targets. Using Particle-In-Cell simulations, we have studied in detail ion acceleration with high intensity laser pulses interacting with low density plasmas. A two-step acceleration process can be triggered: first, ions are accelerated in volume by electric fields generated by hot electrons, second, the ion energy is boosted in a strong electrostatic shock. 2D and 3D simulations show the potential of this regime. It is possible to model separately these two steps. In the first step a hot electron population and a descending density profile are necessary, and the second step develops if a fast proton wave enters in a low density plasma.  
 
MOP154 Prospects for Proton Accelerators Driven by the Radiation Pressure from a Sub-PW CO2 Laser proton, plasma, ion, target 379
 
  • M.N. Polyanskiy, I. Ben-Zvi, I. Pogorelsky, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  • Z. Najmudin
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
 
  Funding: DOE
Laser acceleration of ion beams is normally realized via irradiating thin-foil targets with near-IR solid-state lasers with up to petawatt (PW) peak power. Despite demonstration of significant achievements, further progress towards practical application of such beam sources is hindered by the challenges inherent in constructing still more intense and higher-contrast lasers. Our recent studies of the radiation pressure acceleration indicate that the combination of a 10-μm CO2 laser with a gas jet target offers a unique opportunity for a breakthrough in the field. Strong power scaling of this regime holds the promise of achieving the hundreds of MeV proton beams with just sub-PW CO2 laser pulses. Generation of such pulses is a challenging task. We discuss a strategy of the CO2 laser upgrade aimed to providing a more compact and economical hadron source for cancer therapy. This include optimization of the method of the 10μm short-pulse generation, higher amplification in the CO2 gas under combined isotopic and power broadening effects, and the pulse shortening to a few laser cycles (150-200 fs) via self-chirping in the laser-produced plasma and the consecutive dispersive compression.
 
 
MOP159 Ionization-Induced Trapping in Laser-Plasma Accelerators and Synchrotron Radiation from the Betatron Oscillation electron, radiation, injection, simulation 394
 
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
  • D.L. Bruhwiler, E. Cormier-Michel
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by the U.S. DOE Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and NNSA, NA-22, and used the computational resources of NERSC.
Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR).
 
 
MOP161 Undulator-based Laser Wakefield Accelerator Electron Beam Diagnostic undulator, electron, emittance, quadrupole 397
 
  • M.S. Bakeman, E. Esarey, W. Leemans, K. Nakamura, J. Osterhoff, K.E. Robinson, C.B. Schroeder, C. Tóth, J. van Tilborg
    LBNL, Berkeley, California, USA
  • F.J. Grüner, R. Weingartner
    LMU, Garching, Germany
 
  Funding: This work is supported by DTRA and DOE-HEP.
The design and current status of experiments to cou- ple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented.
* W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006).
** C.B. Schroeder et al., Proceedings AAC08 Conference (2008).
*** F. Grüner et al., Appl. Phys. B, 86(3):431–435 (2007).
 
 
MOP194 A Laser-Wire Beam-Energy and Beam-Profile Monitor at the BNL Linac electron, linac, optics, ion 456
 
  • R. Connolly, L. DeSanto, C. Degen, R.J. Michnoff, M.G. Minty, D. Raparia
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work performed under Contract #DE-AC02-98CH10886 under the auspices of the US Department of Energy.
In 2009 a beam-energy monitor was installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. This device measures the energies of electrons stripped from the 40mA H beam by background gas. Electrons are stripped by the 1.7x10-7torr residual gas at a rate of ~2.4x10-8/cm. Since beam electrons have the same velocities as beam protons, the beam proton energy is deduced by multiplying the electron energy by mp/me=1836. A 183.6MeV H beam produces 100keV electrons. In 2010 we installed an optics plates containing a laser and optics to add beam-profile measurement capability via photodetachment. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. The chamber in which the laser light passes through the ion beam is upstream of a dipole magnet which deflects the electrons into a biased retarding-grid (V<125kV) Faraday-cup detector. To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H beam intercepted by the laser. The laser also gives us energy measurements on the 0.2mA polarized proton beam.
 
 
MOP229 Electron Bunch Characterization using Temporal Electric-field Cross-correlation electron, polarization, plasma, coupling 534
 
  • N.H. Matlis, W. Leemans, G.R.D. Plateau, J. van Tilborg
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by DARPA and by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A new single-shot diagnostic is presented for mapping THz spatiotemporal waveforms with high temporal resolu- tion for use in diagnostics of electron bunch temporal pro- files. The THz waveform is encoded using electro-optic sampling onto either the phase or amplitude of a broadband chirped probe pulse, and is recovered using linear spectral interferometry with a temporally-short reader pulse. The technique was used to measure waveforms of coherent, ultrashort THz pulses emitted by electron bunches from a laser-plasma accelerator with sub-50 fs resolution. The presence of strong spatiotemporal coupling in the THz waveforms and of complex temporal electron bunch structure was determined.
 
 
MOP230 Precise Charge Measurement for Laser Plasma Accelerators electron, plasma, diagnostics, target 537
 
  • K. Nakamura, W.E. Byrne, R.J. Donahue, A.J. Gonsalves, C. Lin, J. Osterhoff, D.E. Rodgers, A.R. Smith, T. Sokollik, J. van Tilborg
    LBNL, Berkeley, California, USA
  • W. Leemans
    UCB, Berkeley, California, USA
  • S. Shiraishi
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
 
  Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Cross-calibrations of charge diagnostics are conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). Employed diagnostics are a scintillating screen, activation based mea- surement, and integrating current transformer. The diagnostics agreed within ±8 %, showing that they can provide accurate charge measurements for LPAs provided they are used properly.
 
 
MOP231 Absolute Beam Flux Measurement at NDCX-I Using Gold-Melting-Calorimetry Technique ion, monitoring, heavy-ion, brightness 540
 
  • P.N. Ni, F.M. Bieniosek, S.M. Lidia
    LBNL, Berkeley, California, USA
  • J.R. Welch
    Cornell University, Ithaca, New York, USA
 
  Funding: Supported by the U.S. Department of Energy under Contracts No. DE-AC02-05CH11231 and DE-AC52-07NA27344.
We report on an alternative way to measure beam fluence at NDCX-I, which is necessary for numerical simulation and planning of warm-dense-matter (WDM) experiments. So far the NDCX-I beam fluence has been characterized using a fast Faraday cup, radiation from a scintillator and tungsten foil calorimeter techniques. The present beam intensity is sufficient to melt and partially evaporate a 150 nm thick gold foil. Thermal emission (function of temperature) of the gold foil in the visible spectrum was measured during beam irradiation. A distinct shelf in the thermal emission intensity was observed after 600 ns, indicating that the sample reached the melting temperature. Using known heat capacity and latent heat of melting, the beam flux fully determines the duration of the melting shelf and the moment it appears. Using this technique we estimate an average 260 kW/cm2 beam flux over 10μs, which is consistent with values provided by the other methods.
 
 
MOP238 Laser Compton Proton Polarimetry Revisited photon, proton, electron, scattering 560
 
  • A.N. Stillman
    Private Address, Huntington, USA
 
  Compton polarimetry of polarized proton beams is more feasible now than it was in 1995*, when I first estimated the laser requirements of a polarimeter using the available laser technology. New methods of high energy photon generation make the technique of Compton proton polarimetry a viable option for polarized proton beams. Since the analyzing power of a Compton polarimeter increases with photon energy and the count rate of the polarimeter increases with the laser intensity, the new laser technologies available today imply the construction of a working device with reasonable effort. I estimate the device parameters necessary for a working Compton polarimeter at RHIC using several methods of high energy photon generation.
* Arnold Stillman, in Proceedings of the 1995 Particle Accelerator Conference, 1995, p.2560
 
 
MOP242 Evaluation of Temporal Diagnostic Techniques for Two-bunch FACET Beam plasma, cavity, diagnostics, wakefield 568
 
  • M.D. Litos, M.R. Bionta, V.A. Dolgashev, R.J. England, D. Fritz, A. Gilevich, P. Hering, M.J. Hogan
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which will incorporate a unique two-bunch beam for plasma wakefield acceleration experiments. The results of these experiments will depend strongly on the the inter-bunch spacing as well as the longitudinal profiles of the two bunches. A reliable, single-shot, high resolution measurement of the beam’s temporal profile is necessary to fully quantify the physical mechanisms underlying the beam driven plasma wakefield acceleration. In this study we show that a transverse deflecting cavity is the diagnostic which best meets our criteria.
 
 
MOP278 Ultra Precision Timing System for the Laser Megajoule high-voltage, diagnostics, target, plasma 633
 
  • V. Drouet, M. Luttmann, M. Prat
    CEA, Arpajon, France
 
  This article presents a specific timing system designed for the Laser Megajoule project. This accuracy timing system has to deliver 64 electrical trigger signals with a very low jitter (< 5 ps rms) in order to synchronize the 240 laser pulses on the same target, in single shot mode and over 100 meter distances. After a dimensioning phase leading to the architecture of the system and the selection of components, a prototype was developed providing 8 electrical trigger signals. We expose the architecture and the excellent results achieved on this prototype regarding jitter, thermal drift and delay linearity.  
 
MOP279 Synchronize Lasers to LCLS e- Beam controls, electron, cavity, LLRF 636
 
  • G. Huang
    TUB, Beijing, People's Republic of China
  • J.M. Byrd, L.R. Doolittle, R.B. Wilcox
    LBNL, Berkeley, California, USA
 
  Fiber based synchronization system is used in LCLS to synchronize the laser for pump probe experiment to average electron beam arrival time. Electron bunch arrival time measured by phase cavity is one of the best measurement for FEL X pulse until now. The average bunch arrival time is transmitted through electronic length stabilized fiber link to AMO and other experiment hall. The laser oscillator is phase locked to this reference signal to maintain low jitter and drift between pump and probe. The in loop error shows the jitter is less then 100 fs and meets the experiment requirement.  
 
MOP285 Synchronization and Jitter Studies of a Titanium-sapphire Laser at the A0 Photoinjector gun, feedback, diagnostics, cathode 651
 
  • T.J. Maxwell, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • M.J. Kucera, J. Ruan
    Fermilab, Batavia, USA
 
  Funding: Supported by Fermi Research Alliance, LLC under U.S. Dept. of Energy Contract No. DE-AC02-07CH11359, and Northern Illinois Univ. under US Dept. of Defense DURIP program Contract N00014-08-1-1064.
A new titanium-sapphire laser has recently been installed at the A0 photoinjector for use in ongoing beam generation and ultra-fast beam diagnostics experiments. Where the system is used as the photoinjector drive laser, jitter and drift in the laser pulse time of arrival with respect to the low-level RF master oscillator and other beam components are known to degrade beam performance. These same fluctuations can also impact the temporal resolution of laser-based diagnostics. To resolve this, we present the results of some beam-based timing experiments as well as current progress on a synchronization feedback loop being adapted to the new laser system.
 
 
MOP287 Femtosecond RF Timing in Low Charge Photoinjectors gun, electron, target, cathode 654
 
  • C.M. Scoby, R.K. Li, J.T. Moody, P. Musumeci
    UCLA, Los Angeles, California, USA
 
  Funding: Office of Naval Research Grant No. N000140711174 and US Department of Energy Grant No. DE-FG02-92ER40693.
Photoelectron gun rf parameter mapping is explored as an extension to electro-optic sampling to monitor bunch vs. laser relative time-of-arrival. The method is evaluated for timestamping sub-picocoulomb femtosecond laser-pumped dynamics in graphite via electron diffraction where the required timing resolution is < 10 fs.
*AL Cavalieri, et al. Phys. Rev. Lett. 94, 114801 (2005)
**A Azima, et al. Appl. Phys. Lett. 94, 144102 (2009)
***CM Scoby, et al. PRST-AB 13, 022801 (2010)
****KJ Kim, Rev. Nucl. Inst. Meth. A 275, 2 (1989)
 
 
MOP288 Progress Report on Development of the RING Cavity for Laser-based Charge Stripping of Hydrogen Ions neutron, radiation, ion, recirculation 657
 
  • R. Tikhoplav
    RadiaBeam, Santa Monica, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
 
  Charge stripping of hydrogen ions is the first stage of any high intensity proton accelerator. To achieve higher-charge proton sources, the stripping efficiency must be improved, especially in the context of the Spallation Neutron Source at Oak Ridge National Laboratory. A method based on laser-ion interaction has a great potential for increasing efficiency. The approach of this proposed project is to design a laser cavity based on the Recirculation Injection by Nonlinear Gating (RING) technique. This paper reports on the progress of the development of the RING cavity.  
 
TUOBN1 Laser Wakefield Acceleration Beyond 1 GeV using Ionization Induced Injection electron, injection, plasma, simulation 707
 
  • K.A. Marsh, C.E. Clayton, C. Joshi, N. Lemos, W. Lu, W.B. Mori, A.E. Pak
    UCLA, Los Angeles, California, USA
  • F. Albert, T. Doeppner, C. Filip, D.H. Froula, S.H. Glenzer, B.B. Pollock, D. Price, J.E. Ralph
    LLNL, Livermore, California, USA
  • R.A. Fonseca, S.F. Martins
    Instituto Superior Tecnico, Lisbon, Portugal
  • L.O. Silva
    IPFN, Lisbon, Portugal
 
  Funding: Supported by DOE Grants No. DE-AC52-07NA27344, DE-FG03-92ER40727, DE-FG02-92ER40727, DE-FC02-07ER41500, DE-FG52-09NA29552, NSF Grants No. PHY-0936266, PHY-0904039 and FCT, Por., No. SFRH/BD/35749/2007
A series of laser wakefield accelerator experiments leading to electron energy exceeding 1 GeV are described. Theoretical concepts and experimental methods developed while conducting experiments using the 10 TW Ti:Sapphire laser at UCLA were implemented and transferred successfully to the 100 TW Calisto Laser System at the Jupiter Laser Facility at LLNL. To reach electron energies greater than 1 GeV with current laser systems, it is necessary to inject and trap electrons into the wake and to guide the laser for more than 1 cm of plasma. Using the 10 TW laser, the physics of self-guiding and the limitations in regards to pump depletion over cm-scale plasmas were demonstrated. Furthermore, a novel injection mechanism was explored which allows injection by ionization at conditions necessary for generating electron energies greater than a GeV. The 10 TW results were followed by self-guiding at the 100 TW scale over cm plasma lengths. The energy of the self-injected electrons, at 3x1018 cm-3 plasma density, was limited by dephasing to 720 MeV. Implementation of ionization injection allowed extending the acceleration well beyond a centimeter and 1.4 GeV electrons were measured.
 
slides icon Slides TUOBN1 [2.488 MB]  
 
TUOBN6 Production of 25 MeV Protons in CO2 Laser-Plasma Interactions in a Gas Jet plasma, proton, ion, target 721
 
  • D.J. Haberberger, C. Gong, C. Joshi, S. Tochitsky
    UCLA, Los Angeles, California, USA
 
  Funding: This work is supported by DOE grant DE-FG02-92ER40727 and NSF grant PHY-0936266
At the Neptune Laboratory at UCLA, we have developed a high-power CO2 MOPA laser system which produces world record multi-terawatt 10um pulses. The CO2 laser pulses consist of a train of 3ps pulses separated by 18ps, each with a peak power of up to 4TW and a total pulse train energy of ~100J. These relativistic laser pulses are applied for Laser Driven Ion Acceleration in an H2 gas jet operated around the critical density of 1019 cm-3 for 10um light using the Target Normal Sheath Acceleration mechanism. The laser is focused into the gas jet reaching a normalized field strength of a0~2 in vacuum. For these conditions, protons with a maximum energy of 25MeV and a narrow energy spread of ΔE/E < 1% are recorded. Initial analysis of these experimental results shows a stronger scaling of the proton energy than that predicted from the ponderomotive force, and highlights the importance of an accumulated effect of multiple CO2 laser pulses lasting over 100ps. The temporal dynamics of the overdense plasma slab are probed with a picosecond 532nm pulse and the results will be discussed.
 
 
TUOBS1 Technical Challenges in the Linac Coherent Light Source, Commissioning and Upgrades undulator, electron, photon, linac 724
 
  • Z. Huang, J.N. Galayda
    SLAC, Menlo Park, California, USA
  • P.A. Heimann
    LBNL, Berkeley, California, USA
 
  Funding: DOE
Five months after first lasing in April 2009, the Linac Coherent Light Source (LCLS) began its first round of x-ray experiments. The facility rapidly attained and surpassed its design goals in terms of spectral tuning range, peak power, energy per pulse and pulse duration. There is an ongoing effort to further expand capabilities while supporting a heavily subscribed user program. The facility continues to work toward new capabilities such as multiple-pulse operation, pulse durations in the femtosecond range, and production of >16 keV photons by means of a second-harmonic “afterburner” undulator. Future upgrades will include self-seeding and polarization control. The facility is already planning to construct a major expansion, with two new undulator sources and space for four new experiment stations.
 
slides icon Slides TUOBS1 [12.513 MB]  
 
TUOCN3 Application of the Eigen-Emittance Concept to Design Ultra-Bright Electron Beams emittance, electron, cathode, free-electron-laser 752
 
  • L.D. Duffy, K. Bishofberger, B.E. Carlsten, S.J. Russell, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
  • A. Dragt
    UMD, College Park, Maryland, USA
  • R.D. Ryne
    LBNL, Berkeley, California, USA
 
  Funding: We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.
Using correlations at the cathode to tailor the beam’s eigen-emittances is a recent concept made useful by the symplectic nature of Hamiltonian systems. While introducing correlations does not change the overall 6-dimensional phase space volume, it can change the partitioning of this volume into the longitudinal and two transverse emittances, which become the eigen-emittances if the initial correlations are removed. In principle, this technique can be used to generate beams with highly asymmetric emittances, such as those needed for the next generation of very hard X-ray free-electron lasers. Based on linear correlations, the applicability of this approach is limited by the magnitude of nonlinear effects in photoinjectors. We review the eigen-emittance concept and present a linear eigen-emittance design leading to a highly partitioned, and transversely ultra-bright, electron beam. We also present numerical tools to examine the evolution of the eigen-emittances in realistic accelerator structures and results indicating how much partitioning is practical.
 
slides icon Slides TUOCN3 [0.530 MB]  
 
TUOCS5 A Next Generation Light Source Facility at LBNL FEL, linac, electron, photon 775
 
  • J.N. Corlett, B. Austin, K.M. Baptiste, J.M. Byrd, P. Denes, R.J. Donahue, L.R. Doolittle, R.W. Falcone, D. Filippetto, D.S. Fournier, J. Kirz, D. Li, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G. Penn, M. Placidi, S. Prestemon, D. Prosnitz, J. Qiang, A. Ratti, M.W. Reinsch, F. Sannibale, D. Schlueter, R.W. Schoenlein, J.W. Staples, T. Vecchione, M. Venturini, R.P. Wells, R.B. Wilcox, J.S. Wurtele
    LBNL, Berkeley, California, USA
  • A.E. Charman, E. Kur
    UCB, Berkeley, California, USA
  • A. Zholents
    ANL, Argonne, USA
 
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a multi‐beamline soft x‐ray FEL array powered by a 2 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds.
 
slides icon Slides TUOCS5 [4.758 MB]  
 
TUP013 A Concept Design of a Compton Scattering Light Source based on the HLS Electron Storage Ring electron, photon, scattering, storage-ring 835
 
  • X.C. Lai, H. Hao, H.Q. Huang, W.W. Li, X.Q. Wang, D.R. Xu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Funding: National Natural Science Foundation of China (Contract NO. 11045003)
Hefei Light Source (HLS) is a 2nd generation light source lasering high flux ultraviolet and soft x-ray with 200 MeV to 800 MeV electron beam. To explorer other applications of the electron storage ring of HLS, a concept design of Hefei Compton Scattering Light Source (HCSLS) is proposed. In this paper, Compton Scattring Simulation Code(CSSC), a parallel code based on the analytical method to simulate the Compton scattering between the laser beam and the electron beam, is presented. Using the CSSC, it is computed that HCSLS will produce photons with a total flux of 109 s-1 to 1011 s-1, and energy of 0.07 MeV to 1.15 MeV at the maximum spectral flux density with the 200 MeV to 800 MeV electron beam scattering with a kilo-watts CO2 laser. With a much shorter wave laser beam from an Nd:YVO4 laser, the scattered photons energy at the maximum spectral flux density is improved by a factor of 10, while its flux is reduce by a factor of 100 due to the lower peak laser power.
 
 
TUP019 The S-DALINAC Polarized Injector SPIN - Performance and Results electron, polarization, linac, site 853
 
  • C. Eckardt, T. Bahlo, P. Bangert, R. Barday, U. Bonnes, M. Brunken, C. Burandt, R. Eichhorn, J. Enders, M. Espig, C. Ingenhaag, J. Lindemann, M. Platz, Y. Poltoratska, M. Roth, F. Schneider, H. Schüßler, M. Wagner, A. Weber, B. Zwicker
    TU Darmstadt, Darmstadt, Germany
  • W. Ackermann, W.F.O. Müller, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
 
  Funding: * Work supported by DFG through SFB 634.
At the superconducting 130 MeV Darmstadt electron linac S-DALINAC the new source of polarized electrons uses a GaAs cathode illuminated with pulsed Ti:Sapphire and diode laser light. The electron source had been set up and commissioned at a test stand with a beam line where a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and a chopper-prebuncher system were part of the system. Upon completion of the tests, test stand and beam line were dismantled and re-installed at the S-DALINAC. The new photo injector opens up the potential for experiments with polarized electron and photon beams for nuclear structure studies at low momentum transfers. Various polarimeters will be installed at all experimental sites to monitor the beam polarization. We report on the S-DALINAC, the results from the teststand performance, the implementation of the polarized source and the polarimeter research and development.
* A. Richter, Proc. of the 5th EPAC, Sitges (1996) 110
** Y. Poltoratska et al., AIP Conference Proc. 1149 (2009) 983
*** P. Mohr et al., Nucl. Instr. and Meth. A423 (1999) 480
 
 
TUP025 Two Wien Filter Spin Flipper electron, solenoid, polarization, target 862
 
  • J.M. Grames, P.A. Adderley, J. F. Benesch, J. Clark, J. Hansknecht, R. Kazimi, D. Machie, M. Poelker, M.L. Stutzman, R. Suleiman, Y. Zhang
    JLAB, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new 4pi spin manipulator composed of two Wien filters oriented orthogonally and separated by two solenoids has been installed at the CEBAF/Jefferson Lab photoinjector. The new spin manipulator is used to precisely set the electron spin direction at an experiment in any direction (in or out of plane of the accelerator) and provides the means to reverse, or flip, the helicity of the electron beam on a daily basis. This reversal is being employed to suppress systematic false asymmetries that can jeopardize challenging parity violation experiments that strive to measure increasingly small physics asymmetries [*,**,***]. The spin manipulator is part of the ultra-high vacuum polarized electron source beam line and has been successfully operated with 100keV and 130keV electron beam at high current (>100 microAmps). A unique feature of the device is that spin-flipping requires only the polarity of one solenoid magnet be changed. Performance characteristics of the Two Wien Filter Spin Flipper will be summarized.
* http://hallaweb.jlab.org/parity/prex/
** http://www.jlab.org/qweak/
*** http://hallaweb.jlab.org/12GeV/Moller/
 
 
TUP040 Asset Management Application for a LLRF Control System LLRF, controls, electron, synchrotron 880
 
  • B. Sakowicz, M. Kamiński, D.R. Makowski, P. Mazur, A. Napieralski, A. Piotrowski
    TUL-DMCS, Łódź, Poland
 
  Funding: The research leading to these results has received funding from the Polish National Science Council Grant 642/N-TESLAXFEL/09/2010/0.
In this article an asset management application for a low level radio frequency (LLRF) control system is described. The system was developed to facilitate management of some aspects of controlling a linear accelerator and, among others, provides means to manage and program multiple firmware versions for a large, distributed and frequently changing set of FPGA devices that are present in a control system. The system introduces a multihierarchical tree-based representation of almost all assets involved in accelerator management.*
* Kamiński M., Makowski D., Mazur P., Murlewski J., Sakowicz B.: "Firmware application for LLRF control system based on the Enterprise Service Bus", CADSM 2009, Ukraine, ISBN 978-966-2191-05-9
 
 
TUP063 HOM Measurements with Beam at the Cornell Injector Cryomodule HOM, simulation, cryomodule, pick-up 934
 
  • S. Posen, M. Liepe
    CLASSE, Ithaca, New York, USA
 
  Funding: NSF
The Cornell ERL injector prototype is undergoing commissioning and testing for running unprecedented currents in an electron cw injector. This paper discusses preliminary measurements of HOMs in the injector prototype’s superconducting RF cryomodule. These include HOM spectra up to 30 GHz measured via small antennae located at the HOM beam line absorbers between the SRF cavities. The spectra are compared at different beam currents and repetition rates. The shape of the spectra are compared to ABCI simulations of the loss factor spectrum of the cryomodule beam line. The total HOM power dissipated in the HOM loads was also measured with beam on, which allowed for an estimate of the loss factor. This measurement was accomplished via temperature sensors on the loads, calibrated to input power by heaters on the loads.
 
 
TUP124 Phase Contrast Imaging Using a Single Picosecond X-ray Pulse of the Inverse Compton Source at the BNL Accelerator Test Facility photon, brightness, electron, scattering 1062
 
  • M. Carpinelli
    Università di Sassari and INFN, Sassari, Italy
  • P. Delogu, M. Endrizzi
    INFN-Pisa, Pisa, Italy
  • B. Golosio, P. Oliva
    INFN-Cagliari, Monserrato (Cagliari), Italy
  • I. Pogorelsky, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
 
  Inverse Compton scattering (ICS) X-ray sources are of current interest due to their novel features that enable new methods in medical and biological imaging. As a compelling example of such a possibility, we present an experimental demonstration of single shot inline phase contrast imaging using the ICS source located at the BNL Accelerator Test Facility. The phase contrast effect is clearly observed in the images obtained. Further, its qualities are shown to be in agreement with the predictions of theoretical models through comparison of experimental and simulated images of a set of plastic wires of differing composition and size. We also display an example of application of the technique to single shot phase contrast imaging of a biological sample.  
 
TUP200 Spatial and Temporal Shaping of Picoseconds Drive Laser in Photocathode RF Gun emittance, gun, polarization, electron 1196
 
  • Z.G. He, Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  In this paper, we present experimental spatial and temporal drive laser shaping results by using of a pi-shaper sample and an interferometer setup pulse stacking system. Based on the spatial and temporal shaping results, a scheme for quasi-ellipsoidal shaping and the evolution of critical parameters are also studied.  
 
TUP276 Measurement of Thermal Dependencies of PBG Fiber Properties simulation, acceleration, controls, alignment 1343
 
  • R. Laouar, E.R. Colby, R.J. England, R.J. Noble
    SLAC, Menlo Park, California, USA
 
  Funding: Department Of Energy
Photonic crystal fibers (PCFs) represent a class of optical fibers which have a wide spectrum of applications in the telecom and sensing industries. Currently, the Advanced Accelerator Research Department at SLAC is developing photonic bandgap particle accelerators, which are photonic crystal structures with a central defect used to accelerate electrons and achieve high longitudinal electric fields. Extremely compact and less costly than the traditional accelerators, these structures can support higher accelerating gradients and will open a new era in high energy physics as well as other fields of science. Based on direct laser acceleration in dielectric materials, the so called photonic band gap accelerators will benefit from mature laser and semiconductor industries.
 
 
TUP286 Development and Testing of Carbon Fiber Vacuum Chamber Supports for NSLS-II radiation, alignment, pick-up, vacuum 1364
 
  • B.N. Kosciuk, C. Hetzel, J.A. Kierstead, V. Ravindranath, S.K. Sharma, O. Singh
    BNL, Upton, Long Island, New York, USA
 
  The NSLS-II Synchrotron Light Source, a 3 GeV electron storage ring currently under construction at Brookhaven National Laboratory is expected to provide exceptional orbit stability in order to fully utilize the very small emittance of the electron beam. In order to realize this, the beam position monitor (BPM) pick up electrodes which are part of the orbit feedback system must have a high degree of mechanical and thermal stability. In the baseline design, this would be accomplished by using flexible invar plates to support the multi-pole vacuum chamber at the positions where the BPM pick up electrodes are mounted. However, it was later discovered that the close proximity of the invar supports to the adjacent focusing magnets had an adverse affect on the magnetic fields. To mitigate this issue, we propose the use of carbon fiber composite in place of invar as a low CTE (coefficient of thermal expansion) material. Here we show the design, development and testing of thermally stable composite supports capable of sub-micron thermal stability.  
 
WEOAN1 Accelerator Timing Systems Overview controls, optics, kicker, FEL 1376
 
  • J. Serrano, P. Alvarez, M.M. Lipinski, T. Włostowski
    CERN, Geneva, Switzerland
 
  Timing systems are crucial ingredients for the successful operation of any particle accelerator complex. They are used not only to synchronize different processes but also to time-stamp and ensure overall coherency of acquired data. We describe fundamental time and frequency figures of merit and methods to measure them, and continue with a description of current synchronization solutions for different applications, precisions and geographical coverage, and some examples. Finally, we describe new trends in timing technology and applications.  
slides icon Slides WEOAN1 [1.122 MB]  
 
WEOAN2 Linac Timing, Synchronization, and Active Stabilization electron, FEL, cavity, feedback 1381
 
  • F. Löhl
    CLASSE, Ithaca, New York, USA
 
  Femtosecond stability is required in an increasing number of linear accelerators, especially in free-electron laser facilities, but also in future light sources based on energy-recovery linear accelerators, as well as in future linear collider projects. This paper discusses schemes to synchronize and stabilize the most critical accelerator components in order to obtain such a stability.  
slides icon Slides WEOAN2 [4.441 MB]  
 
WEOBS1 The Berkeley Lab Laser Accelerator (BELLA): A 10 GeV Laser Plasma Accelerator plasma, electron, simulation, diagnostics 1416
 
  • W. Leemans, R.M. Duarte, E. Esarey, D.S. Fournier, C.G.R. Geddes, D. Lockhart, C.B. Schroeder, C. Tóth, J.-L. Vay, S. Zimmermann
    LBNL, Berkeley, California, USA
 
  An overview is presented of the design of a 10 GeV laser plasma accelerator (LPA) that will be driven by a PW-class laser system and of the BELLA Project, under which the required Ti:sapphire laser system for the acceleration experiments is being installed. The basic design of the 10 GeV stage aims at operation in the quasi-linear regime, where the laser excited wakes are largely sinusoidal and allow acceleration of electrons and positrons. Simulations show that a 10 GeV electron beam can be generated in a meter scale plasma channel guided LPA operating at a density of about 1017 cm-3 and powered by laser pulses containing 30-40 J of energy in a 50-200 fs duration pulse, focused to a spotsize of 50-100 micron. The lay-out of the facility and laser system will be presented as well as the progress on building the facility.  
 
WEOBS3 The Effects of a Density Mismatch in a Two-State LWFA electron, cavity, ion, injection 1421
 
  • B.B. Pollock, F. Albert, C. Filip, D.H. Froula, S.H. Glenzer, J.E. Ralph
    LLNL, Livermore, California, USA
  • C.E. Clayton, C. Joshi, K.A. Marsh, J. Meinecke, A.E. Pak, J.L. Shaw
    UCLA, Los Angeles, California, USA
  • K.L. Herpoldt
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • G.R. Tynan
    UCSD, La Jolla, California, USA
 
  Funding: Work performed under U.S. DOE Contract DE-AC52-07NA27344 and was partially funded by the Laboratory Directed Research and Development Program under project tracking code 06-ERD-056.
A two-stage Laser Wakefield Accelerator (LWFA) has been developed, which utilizes the ionization induced injection mechanism to produce high energy, narrow energy spread electron beams when the electron density is equal in both stages. However, when the densities are not equal these high quality beams are not observed. As the electron density varies across the interface between the adjacent stages the size of the ion cavity is expected to change; this results in either a reduction of the peak electron energy (for a density decrease), or in the exclusion of previously trapped charge from the first wake period (for a density increase). The latter case can be overcome if the interaction length before the density interface exceeds a threshold determined by the densities in each stage, and may provide a mechanism for enhanced energy gain.
 
 
WEOCN1 Laser Based Diagnostics for Measuring H- Beam Parameters diagnostics, ion, emittance, linac 1433
 
  • Y. Liu, A.V. Aleksandrov, W. Blokland, C. Deibele, C.D. Long, A.A. Menshov, J. Pogge, A. Webster, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  • R.A. Hardin
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: sponsored by the Division of Materials Science, U.S. Department of Energy, under contract number DE-AC05-96OR22464 with UT-Battelle Corporation for Oak Ridge National Laboratory
In recent years, a number of laser based H- beam diagnostics systems have been developed in the Spallation Neutron Source (SNS). This talk reviews three types of laser based diagnostics at SNS: the laser wire profile monitors at superconducting linac (SCL), the laser transverse emittance scanner at high energy beam transport (HEBT), and the laser bunch shape monitor at medium energy beam transport (MEBT). Measurement performance will be reported and major technical challenges in the design, implementation, and operation of laser based diagnostics at accelerator facilities will be addressed.
 
slides icon Slides WEOCN1 [4.710 MB]  
 
WEOCN6 Femtosecond Resolved Determination of Electron Beam and XUV Seed Pulse Temporal Overlap in sFLASH electron, radiation, undulator, simulation 1452
 
  • R. Tarkeshian, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • H. Delsim-Hashemi, K. Honkavaara, H. Schlarb, S. Schreiber
    DESY, Hamburg, Germany
  • R. Ischebeck
    PSI, Villigen, Switzerland
 
  sFLASH is a seeded experiment at the Free-Electron Laser FLASH in Hamburg. It uses a 38nm High-Harmonic-Generation (HHG) scheme to seed the FEL-process in a 10 m long variable-gap undulator. The temporal overlap between the electron and HHG pulses is critical to the seeding process. The use of a 3rd harmonic accelerating module provides a high current electron beam with ~400 fs bunch duration. The duration of the HHG laser pulse is ∼20 fs. The desired overlap is achieved in two steps. Firstly, the HHG drive laser is synchronized to the incoherent spontaneous radiation from an upstream undulator with picosecond resolution. Next, the coherent radiation from an undulator is used to determine the exact overlap of the electron beam in a modulator-radiator set-up.  
slides icon Slides WEOCN6 [1.758 MB]  
 
WEODN2 KEK ATF Beam Instrumentation Program feedback, cavity, emittance, kicker 1480
 
  • N. Terunuma
    KEK, Ibaraki, Japan
 
  The Accelerator Test Facility (ATF) in KEK is a research center for studies on issues concerning the injector, damping ring, and beam delivery system for the ILC. It comprises a multibunch-capable RF gun, a 1.3 GeV electron linac, a damping ring, and a test beam line for ILC final focus system (ATF2). Goals of ATF/ATF2 are the achievement of 2 pm vertical emittance, demonstration of a ILC like multi-bunch extraction, achievement of the 37 nm vertical beam size, and stabilization of such beam in a few nano meter level. These targets are supported by R&Ds, such as upgrade of DR BPMs, fast kicker, cavity BPMs, laser-wire, intra-train feedback system (FONT) and a Laser-fringe beam size monitor. To continue providing vital opportunities for accelerator development with the world community, the international collaboration was established.  
slides icon Slides WEODN2 [7.631 MB]  
 
WEODS3 CEBAF 200 kV Inverted Electron Gun high-voltage, electron, vacuum, niobium 1501
 
  • J.M. Grames, P.A. Adderley, J. Clark, J. Hansknecht, M. Poelker, M.L. Stutzman, R. Suleiman, K.E.L. Surles-Law
    JLAB, Newport News, Virginia, USA
  • M. BastaniNejad
    Old Dominion University, Norfolk, Virginia, USA
  • J.L. McCarter
    UVa, Charlottesville, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In addition, DOE-HEP funds this work in support of the ILC R&D program.
Two DC high voltage GaAs photoguns have been built at Jefferson Lab based on a compact inverted insulator design. One photogun provides the polarized electron beam at CEBAF and operates at 130 kV bias voltage. The other gun is used for high average current lifetime studies at a dedicated test facility and has been operated at bias voltage up to 225 kV. The advantages of higher DC voltage for CEBAF include reduced space-charge emittance growth and the potential for prolonged photocathode lifetime. However, a consequence of operating at higher voltages is the increased likelihood of field emission or breakdown, both of which are unacceptable. Highlights of the R&D studies leading toward a production 200keV GaAs photogun for CEBAF will be presented.
 
slides icon Slides WEODS3 [1.360 MB]  
 
WEP189 Compression and Synchronization of an Ultra-short Electron Beam Using a THz Undulator Interaction undulator, electron, radiation, injection 1843
 
  • J.T. Moody, R.K. Li, P. Musumeci, C.M. Scoby, H.L. To
    UCLA, Los Angeles, California, USA
 
  Funding: DOE-BES No. DE-FG02-92ER40693 and DOE-BES No. DE-FG02-07ER46272
Injection of electron beams into laser driven picosecond scale accelerating structures demand highly synchronized electron beams with bunch lengths approaching the femtosecond scale. One-dimensional numerical studies of undulator interactions of 3.5 MeV sub-picosecond electron beams and THz pulse trains produced by optical rectification have shown substantial compression and a reduction in time of arrival jitter with respect to the accelerator drive laser from the scale of hundreds of fs to that of tens of fs. In this paper a THz undulator based compression and synchronization scheme is investigated.
 
 
WEP210 Low Energy Beam Measurements Using PHIL Accelerator at LAL, Comparison with PARMELA Simulations solenoid, simulation, gun, emittance 1885
 
  • J. Brossard, F. Blot, C. Bruni, S. Cavalier, J-N. Cayla, A. Gonnin, M. Joré, P. Lepercq, S.B. Letourneur, B.M. Mercier, H. Monard, C. Prevost, R. Roux, A. Variola
    LAL, Orsay, France
 
  PHIL (“PHoto-Injector at LAL") is a new electron beam accelerator at LAL. This accelerator is dedicated to test and characterize electron RF-guns and to deliver electron beam to users. This machine has been designed to produce and characterise low energy (E<10 MeV), small emittance (e<10 p.mm.mrad), high brilliance electrons bunch at low repetition frequency (n<10Hz). The first beam has been obtained on the 4th of November 2009. The current RF-gun tested on PHIL is the AlphaX gun, a 2.5 cell S-band cavity designed by LAL for the plasma accelerator studies performed at the Strathclyde university. This paper will present the first AlphaX RF-gun characterizations performed at LAL on PHIL accelerator, and will show comparisons between measurements and PARMELA simulations.  
 
WEP244 Growth and Characterization of Bialkali Photocathodes for Cornell ERL Injector vacuum, cathode, gun, ion 1942
 
  • L. Cultrera, I.V. Bazarov, J.V. Conway, B.M. Dunham, Y. Li, X. Liu, K.W. Smolenski
    CLASSE, Ithaca, New York, USA
  • S.S. Karkare, J.M. Maxson
    Cornell University, Ithaca, New York, USA
 
  The requirements of high quantum efficiency in the visible spectral range and that of an increased lifetime as compared to cesiated GaAs can be met by multi-alkali photocathodes, either CsKSb or NaKSb. In this paper we detail the procedures that allow the growth of thin films suitable for the ERL photoinjector operating at Cornell University. Quantum efficiency, spectral response, and surface characterization of deposited samples is presented. A load-locked multi-alkali cathode growth system is also described.  
 
WEP256 Laser-Proton Acceleration as Compact Ion Source proton, simulation, solenoid, electron 1960
 
  • S. Busold, O. Deppert, K. Harres, G. Hoffmeister, F. Nürnberg, M. Roth
    TU Darmstadt, Darmstadt, Germany
  • A. Almomani, C. Brabetz, M. Droba, O.K. Kester, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • V. Bagnoud, W.A. Barth, A. Blazevic, O. Boine-Frankenheim, P. Forck, I. Hofmann, A. Orzhekhovskaya, T. Stöhlker, A. Tauschwitz, W. Vinzenz, S.G. Yaramyshev
    GSI, Darmstadt, Germany
  • T.J. Burris-Mog, T.E. Cowan
    HZDR, Dresden, Germany
  • A. Gopal, S. Herzer, O. Jäckel, B. Zielbauer
    HIJ, Jena, Germany
  • T. Herrmannsdoerfer, M. Joost
    FZD, Dresden, Germany
  • M. Kaluza
    IOQ, Jena, Germany
 
  Preparatory work is presented in the context of the upcoming LIGHT project, which is dedicated to build up a test stand for injecting laser accelerated protons into conventional accelerator structures, located at GSI Helmholtzcenter for Heavy Ion Research (Darmstadt, Germany). In an experimental campaign in 2010, a beam of 8.4×109 protons with 170 ps pulse duration and (6.7±0.1) MeV particle energy could be focused with the use of a pulsed high-field solenoid. Collimation and transport of a 300 ps proton bunch containing 3×109 protons with (13.5±0.5) MeV particle energy over a distance of 407 mm was also demonstrated. Parallel simulation studies of the beam transport through the solenoid are in good agreement with the experiment.  
 
WEP264 Laser Ion Source With Long Pulse Width for RHIC-EBIS ion, solenoid, plasma, ion-source 1972
 
  • K. Kondo, M. Okamura
    BNL, Upton, Long Island, New York, USA
  • T. Kanesue
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and by the National Aeronautics and Space Administration.
The Electron Beam Ion Source (EBIS) at Brookhaven National Laboratory is a new heavy ion-projector for RHIC and NASA Space Radiation Laboratory. Laser Ion Source (LIS) with solenoid can supply many kinds of ion from solid targets and is suitable for long pulse length with low current as ion provider for RHIC-EBIS. In order to understand a plasma behavior for fringe field of solenoid, we measure current, pulse width and total ion charges by a new ion probe. The experimental result indicates that the solenoid confines the laser ablation plasma transversely.
 
 
WEP280 Development of an Ultra-Low-Emittance RF PhotoInjector for a Future X-Ray FEL Oscillator emittance, cavity, gun, space-charge 2005
 
  • X.W. Dong, K.-J. Kim, N. Sereno, C.-X. Wang, A. Zholents
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC02-06CH11357.
The proposed x-ray free-electron laser oscillator* requires continuous electron bunches with ultra-low normalized transverse emittance of less than 0.1 micrometer, a bunch charge of 40 pC, an rms uncorrelated energy spread of less than 1.4 MeV, produced at a rate between 1 MHz to 10 MHz. The bunches are to be compressed to an rms length of ~1 ps and accelerated to the final energy of 7 GeV. In this paper, we discuss a design for an ultra-low-emittance injector based on a 325-MHz room-temperature rf cavity and a Cs2Te photocathode. The results of initial optimizations of the beam dynamics with a focus on extracting and preserving ultra-low emittance will be presented.
* K.-J. Kim et al., Phys. Rev. Lett. 100, 244802 (2008).
 
 
WEP284 Performance Study of K2CsSb Photocathode inside a DC High Voltage Gun gun, high-voltage, cathode, vacuum 2017
 
  • T. Rao, J. Smedley
    BNL, Upton, Long Island, New York, USA
  • J.M. Grames, R.R. Mammei, J.L. McCarter, M. Poelker, R. Suleiman
    JLAB, Newport News, Virginia, USA
 
  Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under grant DE-FG02-08ER41547.
In the past decade, there has been considerable interest in the generation of tens of mA average current in a photoinjector. Until recently, GaAs:Cs cathodes and K2CsSb cathodes have been tested successfully in DC and RF injectors respectively for this application. Our goal is to test the GaAs:Cs in RF injector and the K2CsSb cathode in the DC gun in order to widen our choices. Since the multialkali cathode is a compound with uniform stochiometry over its entire thickness, we anticipate that the life time issues seen in GaAs:Cs due surface damage by ion bombardment would be minimized with this material. Hence successful operation of the K2CsSb cathode in DC gun could lead to a relatively robust electron source capable of delivering ampere level currents. In order to test the performance of K2CsSb cathode in a DC gun, we have designed and built a load lock system that would allow the fabrication of the cathode at BNL and its testing at JLab. In this paper, we will present the design of the load-lock system, cathode fabrication, and the cathode performance in the preparation chamber and in the DC gun.
 
 
WEP289 The Impact of Laser Polarization in Multiphoton Photoemission from a Copper Cathode cathode, polarization, electron, emittance 2026
 
  • R.K. Li, J.T. Moody, P. Musumeci, C.M. Scoby, H.L. To, M.T. Westfall
    UCLA, Los Angeles, California, USA
 
  Multiphoton photoemission from a copper cathode has been recently demonstrated to be a simple and efficient method to generate high quality electron beams. To further improve this scheme to achieve higher charge yielding efficiency and lower intrinsic emittance, we explored the effects of laser polarization at oblique incidence. Charge yields of s and p polarization from coated and uncoated cathodes were measured. The vectorial photoelectric effect was observed on the uncoated cathode but much less evident on the coated one, suggesting that surface properties are critical to the vectorial effect and in general important in photoemission. The results not only are useful in the optimization of an rf photoinjector, but also allow deeper understanding of the photoemission physics.
* P. Musumeci et al., Phys. Rev. Lett. ZeHn4, 084801 (2010).
** P. Musumeci et al., Phys. Rev. Lett. ZeHn0, 244801 (2008).
 
 
WEP295 Status of Laser Stripping at the SNS optics, linac, quadrupole, injection 2035
 
  • T.V. Gorlov, A.V. Aleksandrov, V.V. Danilov
    ORNL, Oak Ridge, Tennessee, USA
  • Y. Liu
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.
This paper presents an overview of experimental and theoretical studies on laser stripping that have been conducted up to the present time in the SNS project. The goal of this work is to develop techniques to achieve the experimental preconditions necessary for the successful realization of a future intermediate experiment on laser stripping. The experimental work consists of the tuning and measurement of H־ beam parameters in readiness for the intermediate experiment, and also takes into account the features and possibilities of the SNS accelerator.
 
 
THOBN4 Experiment to Demonstrate Acceleration in Optical Photonic Bandgap Structures wakefield, simulation, electron, acceleration 2067
 
  • R.J. England, E.R. Colby, R. Laouar, C. McGuinness, D. Mendez, C.-K. Ng, J.S.T. Ng, R.J. Noble, K. Soong, J.E. Spencer, D.R. Walz, Z. Wu, D. Xu
    SLAC, Menlo Park, California, USA
  • E.A. Peralta
    Stanford University, Stanford, California, USA
 
  Funding: This work was funded by Department of Energy Grants DE-AC02-76SF00515, DE-FG06-97ER41276.
Optical scale dielectric structures offer a promising medium for high-gradient, compact, low-cost acceleration of charged particles. An experimental program is underway at the SLAC E163 facility to demonstrate acceleration in photonic bandgap structures driven by short laser pulses. We present initial experimental results, discuss structure and experimental design, and present first estimates of achievable gradient.
 
slides icon Slides THOBN4 [5.925 MB]  
 
THOBN6 Wakefield Breakdown Test of a Diamond-Loaded Accelerating Structure wakefield, vacuum, simulation, acceleration 2074
 
  • S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • M.E. Conde, D.S. Doran, W. Gai, J.G. Power, Z.M. Yusof
    ANL, Argonne, USA
 
  Funding: DOE SBIR
Diamond has been proposed as a dielectric material for dielectric loaded accelerating (DLA) structures. It has a very low microwave loss tangent, the highest available thermoconductive coefficient and high RF breakdown field. In this paper we report the results from a wakefield breakdown test of diamond-loaded rectangular accelerating structure and development of a cylindrical diamond DLA. We expect to achieve field levels on the order of 100 MV/m in the structure using the 100nC beam at the Argonne Wakefield Accelerator Facility. Single crystal diamond plates produced by chemical vapor deposition (CVD) are used in the structure. The structure is designed to yield up to 0.5 GV/m fields on the diamond surface to test it for breakdown. A surface analysis of the diamond is performed before and after the beam test.
 
slides icon Slides THOBN6 [1.629 MB]  
 
THOBS3 Magnetic Alignment of Pulsed Solenoids using the Pulsed Wire Method solenoid, alignment, ion, induction 2087
 
  • D. Arbelaez, J.W. Kwan, T.M. Lipton, A. Madur, W.L. Waldron
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy prepared by LBNL under Contract No. DE-AC02-05CH11231.
A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 μm. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression eXperiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 μm of the induction cell axis has been demonstrated.
 
slides icon Slides THOBS3 [3.246 MB]  
 
THOCN1 Cathodes for Photoemission Guns electron, gun, emittance, vacuum 2099
 
  • L. Cultrera
    CLASSE, Ithaca, New York, USA
 
  The last decade has seen a considerable interest in pursuit and realization of novel light sources such as Free Electron Lasers and Energy Recovery Linacs that promise to deliver unprecedented quality x-ray beams. The performance of these machines is strongly related to the brightness of the electron beam generating the x-rays. The brightness of the electron beam itself is mainly limited by the physical processes by which electrons are generated. For laser based photoemission sources this limit is ultimately related to the properties of photocathodes. In this paper an overview of the recent progress on photocathode development for photoemission electron sources is presented.  
 
THP002 Re-Circulated Inverse Compton Scattering X-ray Source for Industrial Applications electron, photon, recirculation, cavity 2139
 
  • A.Y. Murokh, R.B. Agustsson, S. Boucher, P. Frigola, T. Hodgetts, A.G. Ovodenko, M. Ruelas, R. Tikhoplav
    RadiaBeam, Santa Monica, USA
  • M. Babzien, O.V. Chubar, T.V. Shaftan, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
 
  An experiment is under way at the Accelerator Test Facility (ATF) at BNL to demonstrate inverse Compton scattering in a pulse-train regime. A photoinjector generated electron beam pulse train is scattered by a recirculating laser pulse in a novel resonant configuration termed Recirculation Injection by Nonlinear Gating (RING). The goal of the experiment is to demonstrate strong enhancement of the ICS photon flux through laser recirculation. The project status is presented, and the long-term outlook is discussed with emphasis on the medical and security applications.  
 
THP038 Development of Laser Compton Scattering X-ray Source on the Basis of Compact Electron Linac electron, cavity, scattering, gun 2187
 
  • R. Kuroda, E. Miura, H. Toyokawa, K. Yamada, E. Yamaguchi
    AIST, Tsukuba, Ibaraki, Japan
  • M. Kumaki
    RISE, Tokyo, Japan
 
  A compact hard X-ray source via laser Compton scattering is required for biological, medical and industrial science because it has many benefits about generated X-rays such as short pulse, quasi-monochromatic, energy tunability and good directivity. Our X-ray source is conventionally the single collision system between an electron pulse and a laser pulse. To increase X-ray yields, we have developed a multi-collision system with a multi-bunch electron beam and a laser optical cavity. The multi-bunch beam will be generated from a Cs-Te photocathode rf gun sytem using a multi-pulse UV laser. The laser optical cavity will be built like the regenerative amplification including the collision point between the electron pulse and the laser pulse to enhance the laser peak power per 1 collision on laser Compton scattering. In this conference, we will describe the results of preliminary experiments for the multi-collision system and future plans.  
 
THP039 Development of a High-power THz-TDS System on the Basis of a Compact Electron Linac electron, linac, synchrotron, synchrotron-radiation 2190
 
  • M. Kumaki, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • R. Kuroda, H. Toyokawa, K. Yamada
    AIST, Tsukuba, Ibaraki, Japan
 
  The high-power terahertz time-domain spectroscopy (THz-TDS) system has been developed on the basis of a compact S-band electron linac at AIST, Japan. The linac whose injector is a photocathode rf gun generates about a 40 MeV, 1 nC electron bunch. The bunch is compressed into less than 1ps with a magnetic compressor. It is bended by a 90-degree bending magnet, which causes generation of the THz coherent synchrotron radiation (CSR). It has useful characteristics such as high power, a short pulse and continuous spectrum. In particular, peak power of THz-CSR is estimated to be about 106 times larger than that of the conventional THz source on the basis of the mode-locked fs laser. The THz-TDS is based on the EO sampling methods with the pump-probe technique. The frequency spectrum is obtained by Fourier transform of the measured temporal THz waveform. In addition, it is applied to the ultra-short bunch length monitor by analysing the THz spectrum. In this paper, we will describe details of our system and preliminary experimental results.  
 
THP044 Linear Accelerator Design Study with Direct Plasma Injection Scheme for Warm Dense Matter ion, target, plasma, heavy-ion 2199
 
  • K. Kondo, M. Okamura
    BNL, Upton, Long Island, New York, USA
  • T. Kanesue
    Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Warm Dense Matter (WDM) is a growing rapidly science field, which is related to planetary science and inertial fusion. It is difficult to expect the behavior because the state with high density and low temperature is completely different from ideal condition. The well-defined WDM generation is required to understand it. Moderate energy ion beam (~ 0.3 MeV/u) slightly above Bragg peak is an advantageous method for WDM because of the uniform energy deposition. Direct Plasma Injection Scheme (DPIS) with a linear accelerator has a potential for the beam parameter. The design of linear accelerator for WDM is presented.
 
 
THP045 Proposed Facility Layout for MaRIE electron, radiation, proton, undulator 2202
 
  • J.A. O'Toole, M.J. Bodelson, J.L. Erickson, R.W. Garnett, M.S. Gulley
    LANL, Los Alamos, New Mexico, USA
 
  The MaRIE (Matter-Radiation Interactions in Extremes) experimental facility will be used to advance materials science by providing the tools scientists need to develop materials that will perform predictably and on demand for currently unattainable lifetimes in extreme environments. The Multi-Probe Diagnostic Hall (MPDH) will create probes of matter using both photon- and proton-based diagnostics. The Fission and Fusion Materials Facility (F3) will provide capabilities for materials irradiation studies, subjecting materials to radiation extremes that are present in fission and fusion environments. The Making, Measuring, and Modeling Materials (M4) Facility will foster discovery by design of next-generation materials that will perform with better durability in extreme environments. MaRIE features a 20-GeV electron linac for an X-ray driver. Five X-ray beams will be delivered to the experimental areas. The facility will also deliver an electron beam to MPDH. The existing LANSCE proton beam will be delivered to MPDH and F3 in addition to the existing LANSCE areas. Multiple high power lasers will deliver beams to MPDH. This paper will provide an overview of the MaRIE facility layout.  
 
THP073 Simulations of Emittance Measurement at CLIC emittance, collider, simulation, quadrupole 2270
 
  • Yu.A. Kubyshin, H. Garcia
    UPC, Barcelona, Spain
  • E. Marin, D. Schulte, F. Stulle
    CERN, Geneva, Switzerland
 
  A proposal for a CLIC emittance measurement line using laser-wire beam profile monitors is presented. Results of simulations and optimizations are given. Estimates of the impact of beam size as well as statistical and machine-related errors on the measurement accuracy are discussed.  
 
THP107 Source of Microbunching at BNL NSLS Source Development Laboratory linac, electron, FEL, wakefield 2324
 
  • S. Seletskiy, Y. Hidaka, J.B. Murphy, B. Podobedov, H.J. Qian, Y. Shen, X.J. Wang, X. Yang
    BNL, Upton, Long Island, New York, USA
 
  We report experimental studies of the origins of electron beam microbunching instability at BNL Source Development Laboratory (SDL). We eliminated laser-induced microbunching by utilizing an ultra-short photocathode laser. The measurements of the resulting electron beam led us to conclude that, at SDL, microbunching arising from shot noise is not amplified to any significant level. Our results demonstrated that the only source of microbunching instability at SDL is the longitudinal modulation of the photocathode laser pulse. Our work shows that assuring a longitudinally smoothed photocathode laser pulse allows mitigating microbunching instability at a typical FEL injector with a moderate microbunching gain.  
 
THP126 Obtaining Sub-Picosecond X-Ray Pulses in the Advanced Photon Source Using Laser Slicing electron, wiggler, photon, radiation 2357
 
  • A. Zholents, M. Borland
    ANL, Argonne, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The laser slicing technique* has been successfully applied at several low- to medium-energy storage ring light sources to create sub-picosecond pulses of x-rays. Application to high-energy storage rings has been considered problematic because of the required average laser power. However, because of on going advances in laser technology, this technique is now within reach at light sources like the Advanced Photon Source (APS), which operates at 7 GeV. In this paper, we analyze the potential performance of laser slicing at the APS, and compare it to alternatives such as deflecting cavities.
* R. W. Schoenlien et al., Science, 287, 2237(2000).
 
 
THP136 Short Pulse Generation by Laser Slicing at NSLSII photon, electron, lattice, wiggler 2381
 
  • L.-H. Yu, A. Blednykh, O.V. Chubar, W. Guo, S. Krinsky, Y. Li, T.V. Shaftan, G.M. Wang, F.J. Willeke, L. Yang
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by DOE contract DE-AC02-98CH10886.
We propose an upgrade R&D project for NSLSII to generate sub-pico-second short x-ray pulses using laser slicing. In this paper we discuss the basic parameters for this system and present a specific example for a viable design and its performance. Since the installation of the laser slicing system into the storage ring will break the symmetry of the lattice, we demonstrate it is possible to recover the dynamical aperture to the original design goal of the ring.
 
 
THP141 On the Problem of Threshold Characteristics for FELWI electron, wiggler, FEL, undulator 2387
 
  • K.B. Oganesyan
    YerPhI, Yerevan, Armenia
  • A.I. Artemyev, D.N. Klochkov
    GPI, Moscow, Russia
  • G. Kurizki
    Weizmann Institute of Science, Rehovot, Israel
  • Y. Rostovtsev
    University of North Texas, Denton, Texas, USA
  • M. Scully
    Texas A&M University, College Station, Texas, USA
 
  Funding: ISTC A-1602
For a free-electron laser without inversion (FELWI), es- timates of the threshold laser power are found. The large- amplification regime should be used to bring an FELWI above the threshold laser power.
 
 
THP148 Experimental Investigation of Superradiance in a Tapered Free-Electron Laser Amplifier undulator, electron, simulation, radiation 2396
 
  • Y. Hidaka, J.B. Murphy, B. Podobedov, S. Seletskiy, Y. Shen, X.J. Wang, X. Yang
    BNL, Upton, Long Island, New York, USA
 
  We report experimental studies of the effect of undulator tapering on superradiance in a single-pass high- gain free-electron laser (FEL) amplifier. The experiments were performed at the Source Development Laboratory (SDL) of National Synchrotron Light Source (NSLS). Efficiency was nearly tripled with tapering. Both the temporal and spectral properties of the superradiant FEL along the uniform and tapered undulator were experimentally characterized using frequency-resolved optical gating (FROG) images. Numerical studies predicted pulse broadening and spectral cleaning by undulator tapering Pulse broadening was experimentally verified. However, spectral cleanliness degraded with tapering.
* T. Watanabe et al, Phys. Rev. Lett. 98, 034802 (2007).
** X.J. Wang et al, Phys. Rev. Lett. 103, 154801 (2009).
 
 
THP149 Amplification of Current Density Modulation in a FEL with an Infinite Electron beam electron, FEL, radiation, free-electron-laser 2399
 
  • G. Wang, V. Litvinenko, S.D. Webb
    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.
We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with a kappa-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain.
 
 
THP153 Manipulating the FEL gain process with an In-cavity Aperture System FEL, cavity, electron, wiggler 2405
 
  • J.Y. Li, B. Jia, S.F. Mikhailov, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • S. Huang
    PKU/IHIP, Beijing, People's Republic of China
 
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The 53.73 meters long free-electron laser (FEL) resonator at Duke University consists of two concave mirrors with the similar radius of curvature. The downstream mirror receives not only the fundamental but also higher order harmonic radiation (typically in the UV and VUV range) emitted by relativistic electrons in the magnetic field of wigglers. The power load of wiggler radiation on this mirror can thermally deform and permanently damage the multi-layer coating of the mirror, therefore, limiting the maximum power of the FEL operation and reducing the mirror lifetime. To mitigate these problems, a water-cooled aperture system has been installed inside the FEL resonator. This aperture system has been used to prevent most of off-axis helical wiggler radiation from reaching the downstream FEL mirror. It has also been used to manipulate the FEL gain process by increasing the FEL beam diffraction loss inside the resonator. In principle, this aperture system can be used as an independent FEL gain control device for FEL operation. This paper reports our preliminary study of the FEL operation using the in-cavity apertures to manipulate the FEL gain process.
 
 
THP155 Experience of FEL Mirror Degradation at the Duke FEL and HIGS Facility FEL, wiggler, cavity, radiation 2408
 
  • S.F. Mikhailov, J.Y. Li, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
 
  Funding: This work is supported by the US DoE grant #DE-FG02-97ER41033
The Duke FEL and High Intensity Gamma-ray Source (HIγS) are operated in the range of electron beam energies of 0.24 - 1.2 GeV and photon beam wavelengths of 190-1060 nm. The range of gamma-beam energies currently produced by HIγS facility is from 1MeV to about 100 MeV, with the maximum total gamma-flux of up to 3*1010 gammas per second around 10 MeV. Production of this high level gamma-ray flux requires an average FEL photon beam power inside the FEL resonator at one kilowatt or more. The high power FEL operation causes degradation of the FEL mirrors, especially when operating the FEL in the UV and VUV region at a high electron beam energy. To ensure reliable HIγS operation, we developed a comprehensive program to continuously monitor the performance of the FEL mirrors. This program enabled us to use a particular set of FEL mirrors for a few hundreds hours of high gamma-flux operation with predictable performance. In this work, we discuss sources and consequences of the mirror degradation for a variety of wavelengths. We also present estimates of the mirror life time as a function of the FEL wavelength, photon and gamma-ray polarization, and total gamma-flux.
 
 
THP164 Orbital Angular Momentum Light Generated via FEL at NLCTA undulator, electron, bunching, simulation 2420
 
  • A. Knyazik, E. Hemsing, A. Marinelli, J.B. Rosenzweig
    UCLA, Los Angeles, USA
 
  A scheme to create coherent light with orbital angular momentum (OAM) using Free Electron Laser (FEL) at NLCTA is proposed. An 795 nm light co-propagating with relativistic unmodulated electron beam is fed through a helical undulator tuned to the second harmonic of the laser, which acts as a pre-buncher that helically micro-bunches the beam, modulating it in energy. The energy modulation is transferred to helical density modulation by propagating through a longitudinally dispersive section, such as a chicane. Finally the helical density 3-D modulated electron beam is sent through a second undulator resonant at light’s fundamental frequency, causing the electron beam to radiate OAM light. NLCTA facility has everything to make this experiment, including a planar undulator tuned to the fundamental frequency, except for a helical pre-bunching undulator, which can be easily constructed and installed to generate OAM light at NLCTA. According to simulations generated with Mathematica 7 and Genesis 1.3 a 3 period long pre-buncher will be enough to get out 140 MW of laser power from a seeded 10 MW, after transversing a 1.5 m long planar radiator using electron beam generated by NLCTA.  
 
THP170 Observation and Characterization of Coherent Optical Radiation and Microbunching Instability in the SLAC Next Linear Collider Test Accelerator radiation, undulator, electron, FEL 2426
 
  • S.P. Weathersby, M.P. Dunning, C. Hast, R.K. Jobe, D.J. McCormick, J. Nelson, D. Xiang
    SLAC, Menlo Park, California, USA
 
  The NLC Test Accelerator (NLCTA) at SLAC is currently configured for a proof-of-principle echo-enabled harmonic generation (EEHG) experiment using a 120 MeV beam. During commissioning, unexpected coherent optical undulator radiation (CUR) and coherent optical transition radiation (COTR) was observed when beam is accelerated off-crest and compressed after the chicanes. The CUR and COTR is likely due to a microbunching instability where initial small modulations in the cathode drive laser pulse are compressed and amplified. In this paper we present the observation and characterization of the CUR, COTR and microbunching instability at NLCTA.
* D. Xiang et al., "Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers", PRL 105, 114801, 2010.
 
 
THP171 Demonstration of 3D Effects with High Gain and Efficiency in a UV FEL Oscillator FEL, electron, wiggler, simulation 2429
 
  • S.V. Benson, G.H. Biallas, K. Blackburn, J.R. Boyce, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, A.M. Watson, G.P. Williams, F.G. Wilson, S. Zhang
    JLAB, Newport News, Virginia, USA
 
  Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences, the Office of Naval Research, and Joint Technology Office
We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency.
 
 
THP176 Progress Toward the Wisconsin Free Electron Laser gun, electron, FEL, SRF 2444
 
  • J. Bisognano, R.A. Bosch, D. Eisert, M.V. Fisher, M.A. Green, K. Jacobs, K.J. Kleman, J. Kulpin, G.C. Rogers
    UW-Madison/SRC, Madison, Wisconsin, USA
  • J.E. Lawler, D. Yavuz
    UW-Madison/PD, Madison, Wisconsin, USA
  • R.A. Legg
    JLAB, Newport News, Virginia, USA
 
  Funding: NSF Award No. DMR-0537588 DOE Award No. DE-SC0005264
The University of Wisconsin-Madison/Synchrotron Radiation Center is advancing its design for a seeded VUV/soft X-ray Free Electron Laser facility called WiFEL. To support this vision of an ultimate light source, we are pursuing a program of strategic R&D addressing several crucial elements. This includes development of a high repetition rate, VHF superconducting RF electron gun, R&D on photocathode materials by ARPES studies, and evaluation of FEL facility architectures (e.g., recirculation, compressor scenarios, CSR dechirping, undulator technologies) with the specific goal of cost containment. Studies of high harmonic generation for laser seeding are also planned.
 
 
THP180 Studies of a Linac Driver for a High Repetition Rate X-ray FEL linac, FEL, emittance, simulation 2450
 
  • M. Venturini, J.N. Corlett, L.R. Doolittle, D. Filippetto, C. F. Papadopoulos, G. Penn, D. Prosnitz, J. Qiang, M.W. Reinsch, R.D. Ryne, F. Sannibale, J.W. Staples, R.P. Wells, J.S. Wurtele, M.S. Zolotorev
    LBNL, Berkeley, California, USA
  • A. Zholents
    ANL, Argonne, USA
 
  Funding: Work carried out under Department of Energy contract No. DE-AC02-0SCK11231
We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a point-design for a 1.8 GeV machine tuned for 300~pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.
 
 
THP181 Low Intensity Nonlinear Effects in Compton Scattering Sources electron, scattering, photon, radiation 2453
 
  • F. Albert, S.G. Anderson, C.P.J. Barty, M. Betts, R.R. Cross, C.A. Ebbers, D.J. Gibson, F.V. Hartemann, T.L. Houck, R.A. Marsh, M. J. Messerly, C. Siders, S.S.Q. Wu
    LLNL, Livermore, California, USA
 
  The design and optimization of a Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering source are presented. A new precision source with up to 2.5 MeV photon energies, enabled by state of the art laser and x-band linac technologies, is currently being built at LLNL. Various aspects of the theoretical design, including dose and brightness optimization, will be presented. In particular, while it is known that nonlinear effects occur in such light sources when the laser normalized potential is close to unity, we show that these can appear at lower values of the potential. A three dimensional analytical model and numerical benchmarks have been developed to model the source characteristics, including nonlinear spectra. Since MEGa-ray sources are being developed for precision applications such as nuclear resonance fluorescence, assessing spectral broadening mechanisms is essential.
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
 
 
THP182 Overview of Current Progress on the LLNL Nuclear Photonics Facility and Mono-energetic Gamma-ray Source electron, gun, scattering, photon 2456
 
  • F.V. Hartemann, F. Albert, S.G. Anderson, C.P.J. Barty, A.J. Bayramian, R.R. Cross, C.A. Ebbers, D.J. Gibson, T.L. Houck, R.A. Marsh, D.P. McNabb, M. J. Messerly, C. Siders
    LLNL, Livermore, California, USA
  • C. Adolphsen, T.S. Chu, E.N. Jongewaard, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, F. Wang, J.W. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
A new class of gamma-ray light source based on Compton scattering is made possible by recent progress in accelerator physics and laser technology. Mono-energetic gamma-rays are produced from collisions between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linear accelerator designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable gamma-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. The source will be used to conduct nuclear resonance fluorescence experiments and address a broad range of current and emerging applications in nuclear photoscience. Users include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented, along with important applications.
 
 
THP198 Upgrade of the RF Photo-Injector for the Duke Storage Ring linac, cathode, booster, electron 2489
 
  • V. Popov, J.Y. Li, S.F. Mikhailov, P.W. Wallace, P. Wang, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
 
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The accelerator facility for the Duke FEL and High Intensity Gamma-ray Source (HIGS) consists of a linac pre-injector, a top-off booster injector, and the storage ring. The S-band RF gun with the LaB6 cathode was initially operated in the thermionic mode, producing a long electron beam pulse and a large radiation background. In 1997, the thermionic RF gun was converted to a photo-cathode operation using a nitrogen drive laser for single bunch injection into the storage ring. The photo-cathode operation typically delivers 0.1 nC of charge in a 1 ns long pulse to the linac. Since 2006, substantial improvements have been made to the photo-cathode and the linac, including improvements of the nitrogen drive laser, development of driver laser optical transport and beam monitoring system, and optimization of the cathode heater current to minimize the thermionic emission. In addition, two electron beam charge measurement systems using Faraday cup detectors and sample and hold electronics have been developed. In this work, we will present these new developments and discuss the impact of these upgrades on everyday operation of the linac pre-injector.
 
 
THP199 Raising Photoemission Efficiency with Surface Acoustic Waves electron, photon, linac, lattice 2492
 
  • A. Afanasev
    Hampton University, Hampton, Virginia, USA
  • R.P. Johnson
    Muons, Inc, Batavia, USA
 
  Funding: Supported in part by Muons, Inc.
Current and future synchrotron radiation light sources and free electron laser facilities are in need of improvements in Electron Gun Technology, especially regarding the cost and efficiency of photoinjectors. The generation of Surface Acoustic Waves (SAW) on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the surface of the material. These fields significantly reduce the recombination probability of electrons and holes which can result in enhanced quantum efficiency of photoemission. Additional advantages are provided by the mobility of charge carriers that can be controlled by SAW. It is expected that this novel feature will result in enhanced efficiency of photocathode operation, leading to the production of intense, low emittance electron bunches at a high repetition rate using laser excitation.
 
 
THP200 Photoinjector Beam Dynamics for a Next Generation X-Ray FEL emittance, space-charge, FEL, bunching 2495
 
  • C. F. Papadopoulos, J.N. Corlett, D. Filippetto, G. Penn, J. Qiang, F. Sannibale, J.W. Staples, M. Venturini, R.P. Wells, M.S. Zolotorev
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
In this paper, we will present the status of the beam dynamics simulations for a Next Generation Light Source (NGLS) injector, based on a high repetition rate (1 MHz), high brightness design. A multi-stage beam compression scheme is proposed, based on the concepts of velocity bunching and emittance compensation. For the optimization of the design parameters we use a genetic algorithm approach, and we focus on a mode providing charges of 300 pC, with normalized transverse emittance less than 0.6 microns, suitable to operate a next generation light source based on an X-ray FEL. In addition, we discuss the effects of bunch compression and linearity of the transverse and longitudinal phase space of the beam.
 
 
THP208 Development of Alkali-Based High Quantum Efficiency Semiconductors for Dispenser Photocathodes cathode, electron, FEL, vacuum 2510
 
  • E.J. Montgomery, D.W. Feldman, S.A. Khan, P.G. O'Shea, P.Z. Pan, B.C. Riddick
    UMD, College Park, Maryland, USA
  • K. L. Jensen
    NRL, Washington, DC, USA
 
  Funding: This work is supported by the Office of Naval Research.
Photocathodes as electron beam sources can meet the stringent requirements of high performance FELs, but exhibit a lifetime-efficiency tradeoff. High quantum efficiency (QE) cathodes are typically semiconductors, well described by recently enhanced theory*. Cesium dispenser technology, proven to extend lifetime of tungsten cathodes**, can be extended to high QE via the development of semiconductor coatings which are suitable for rejuvenation. Rejuvenation occurs via controlled cesium diffusion through a sintered substrate to resupply the surface (as described by models of pore*** and surface**** diffusion). Compatible coatings must be thermally stable materials with a cesium-based surface layer. Following standard fabrication processes*****, we discuss alkali antimonides and alkali aurides as cesium dispenser photocathode coatings and analyze future prospects. We also describe improvements to experimental techniques.
*K.L. Jensen et al., (this conference)
**Moody et al., J. Appl. Phys. 102(10), 2010
***B.C. Riddick et al., (this conference)
****P.Z. Pan et al., (this conference)
*****S.A. Khan et al., (this conference)
 
 
THP222 Drive Laser System for the Advanced Photo-Injector Project at the LBNL cathode, electron, emittance, controls 2537
 
  • J. Feng, D. Filippetto, H.A. Padmore, F. Sannibale, R.P. Wells
    LBNL, Berkeley, California, USA
  • M. J. Messerly, M.A. Prantil
    LLNL, Livermore, California, USA
 
  Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
The electron photo-gun of the Advanced Photo-injector EXperiment project (APEX) at the LBNL will be driven by a compact fiber laser for different photo-cathode experiments during the initial phase of the project. The fiber laser, developed at the Lawrence Livermore National Laboratory, is designed to deliver μJ/pulse at 1064 nm system that is frequency doubled to deliver light at 532nm with 1MHz repetition rate and 1ps pulse length optimized for photo-emission with multi-alkali antimonide cathodes. For Cs2Te and diamond amplifier cathodes, the 4th harmonic will be generated by doubling frequency again in a non-linear crystal. Due to the requirement of small emittance for the electron beam, the laser pulse will be shaped in space and time for 532nm and UV lights, in general with a constant intensity in cross section with a sharp radial cutoff, and elliptical or rectangular distribution in the longitudinal plane. Diagnostics of the laser beam itself and of the cathode will be integrated with techniques such as cross- correlation, streak camera, and virtual cathode imaging, not only to monitor the laser pulse but also to provide automated feedbacks.
 
 
THP223 Laser Systems for Livermore's Mono-Energetic Gamma-Ray Source electron, scattering, photon, emittance 2540
 
  • D.J. Gibson, F. Albert, C.P.J. Barty, A.J. Bayramian, C.A. Ebbers, F.V. Hartemann, R.A. Marsh, M. J. Messerly
    LLNL, Livermore, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
A Mono-energetic Gamma-Ray (MEGa-Ray) source, based on Compton scattering of a high-intensity laser beam off a highly relativistic electron beam, requires highly specialized laser systems. To minimize the bandwidth of the gamma-ray beam, the scattering laser must have minimal bandwidth, but also match the electron beam depth of focus in length. This requires a ~1 J, 10 ps, fourier-transform-limited laser system. Also required is a high-brightness electron beam, best provided by a photoinjector. This electron source in turn requires a second laser system with stringent requirements on the beam including flat transverse and longitudinal profiles and fast rise times. Furthermore, these systems must be synchronized to each other with ps-scale accuracy. Using a novel hyper-dispersion compressor configuration, advanced fiber amplifiers, and diode-pumped Nd:YAG amplifiers, we have designed laser systems that meet these challenges for the x-band photoinjector and Compton-scattering source being built at Lawrence Livermore National Laboratory.
 
 
THP224 Progress Report on Development of Novel Ultrafast Mid-IR Laser System FEL, coupling, wiggler, electron 2543
 
  • R. Tikhoplav, A.Y. Murokh
    RadiaBeam, Santa Monica, USA
  • I. Jovanovic
    Penn State University, University Park, Pennsylvania, USA
 
  Of particular interest to X-ray FEL light source facilities is Enhanced Self-Amplified Spontaneous Emission (ESASE) technique. Such a technique requires an ultrafast (20-50 fs) high peak power, high repetition rate reliable laser systems working in the mid-IR range of spectrum (2μm or more). The approach of this proposed work is to design a novel Ultrafast Mid-IR Laser System based on optical parametric chirped-pulse amplification (OPCPA). OPCPA is a technique ideally suited for production of ultrashort laser pulses at the center wavelength of 2 μm. Some of the key features of OPCPA are the wavelength agility, broad spectral bandwidth and negligible thermal load. This paper reports on the progress of the development of the Ultrafast Mid-IR Laser System.  
 
THP225 Characterization and Suppression of the Electromagnetic Interference Induced Phase Shift in the JLab FEL Photo – Injector Advanced Drive Laser System FEL, controls, shielding, electron 2546
 
  • F.G. Wilson, D.W. Sexton, S. Zhang
    JLAB, Newport News, Virginia, USA
 
  The new drive laser for the photo-cathode gun used in the JLab FEL facility had been experiencing various phase shifts on the order of tens of degrees (>20° at 1497 MHz or >40ps) when changing the Advanced Drive Laser (ADL) micro-pulse frequencies. These phase shifts introduce multiple complications when trying to setup the accelerator for operation, ultimately inhibiting the robustness and overall performance of the FEL. Through rigorous phase measurements and systematic characterizations, we discovered the problems could be attributed to EMI coupling into the ADL phase control loop system, and subsequently resolved the issue of phase shift to within tenths of a degree (<0.5° at 1497 MHz or <1ps). The diagnostic method developed and the knowledge gained through the entire process will prove to be invaluable for future designs of similar systems.  
 
FROAN4 Femtosecond RF Gun Based MeV Electron Diffraction electron, gun, emittance, cathode 2558
 
  • J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida
    ISIR, Osaka, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
 
  Ultrafast time-resolved electron diffraction based on a photocathode rf electron gun is being developed in Osaka University to reveal the hidden dynamics of intricate molecular and atomic processes in materials. A new structure rf gun has been developed to generates a low-emittance femtosecond-bunch electron beam, and has been used successfully for the single-shot MeV electron diffraction measurement. The transverse emittance, bunch length and energy spread were measured. The growths of the emittance, bunch length and energy spread due to the rf and the space charge effects in the rf gun were investigated by changing the laser injection phase, the laser pulse width and the bunch charge. The same demonstrations of the electron diffraction measurement were reported.  
slides icon Slides FROAN4 [5.097 MB]