Author: Huang, Z.
Paper Title Page
MOPSO69 Free-Electron Lasers Driven by Laser-Plasma Accelerators Using Decompression or Dispersion 117
 
  • C.B. Schroeder, E. Esarey, W. Leemans, J. van Tilborg
    LBNL, Berkeley, California, USA
  • Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
  • F.J. Grüner, A.R. Maier
    CFEL, Hamburg, Germany
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Laser-plasma accelerators (LPAs) compactly produce fs beams with kA peak current and low (sub-micron) transverse emittance. Presently, the energy spread (percent-level) hinders the FEL application. Slippage of the fs beam in the FEL also suppresses lasing in the soft-x-ray, and longer, wavelength regimes. Given experimentally demonstrated LPA electron beam parameters, we discuss methods of beam phase space manipulation after the LPA to achieve FEL lasing. Decompression is examined as a solution to reduce the slice energy spread and slippage effects. We present a theoretical analysis of the stretched (and chirped) LPA beam in the FEL and determine the optimal decompression. Dispersion, coupled to a transverse gradient undulator (TGU), is also considered to enable LPA-driven FELs. Using a TGU has the advantages of shorter pulse duration, smaller bandwidth, and wavelength stabilization. We present numerical modeling for SASE and seeded XUV and soft x-ray FELs driven by LPAs after beam manipulation (decompression and/or dispersion). Recent advances in LPA performance will be presented, and experimental plans to demonstrate LPA-driven FEL lasing at LBNL will be discussed.
 
 
TUOBNO04
Femtosecond Electron and X-ray Beam Temporal Diagnostics Using an X-band Transverse Deflector at LCLS  
 
  • Y. Ding, C. Behrens, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, T.J. Maxwell, J.W. Wang, M.-H. Wang, J.J. Welch
    SLAC, Menlo Park, California, USA
  • C. Behrens
    DESY, Hamburg, Germany
 
  X-ray free-electron lasers provide ultrashort x-ray pulses for multidisciplinary users. Temporal characterization of these ultrashort pulses with a femtosecond precision remains a challenging topic. At the Linac Coherent Light Source (LCLS), an X-band radio-frequency transverse deflector proposed in 2011 [*] has just been installed and commissioning of the RF system has started. By measuring the electron beam longitudinal phase space between lasing and non-lasing conditions, both the e-beam and x-ray temporal profiles can be reconstructed. We report the latest progress of the commissioning of the deflector and the measurements on the e-beam and x-ray pulse length with this deflector at LCLS. The resolution, stability and operational performance will also be discussed.
[*] Y. Ding et al., Phys. Rev. ST Accel. Beams 14, 120701 (2011)
 
slides icon Slides TUOBNO04 [4.086 MB]  
 
TUOCNO05 Design Concepts for a Next Generation Light Source at LBNL 193
 
  • J.N. Corlett, A.P. Allezy, D. Arbelaez, K.M. Baptiste, J.M. Byrd, C.S. Daniels, S. De Santis, W.W. Delp, P. Denes, R.J. Donahue, L.R. Doolittle, P. Emma, D. Filippetto, J.G. Floyd, J.P. Harkins, G. Huang, J.-Y. Jung, D. Li, T.P. Lou, T.H. Luo, G. Marcus, M.T. Monroy, H. Nishimura, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, S. Paret, G. Penn, M. Placidi, S. Prestemon, D. Prosnitz, H.J. Qian, J. Qiang, A. Ratti, M.W. Reinsch, D. Robin, F. Sannibale, R.W. Schoenlein, C. Serrano, J.W. Staples, C. Steier, C. Sun, M. Venturini, W.L. Waldron, W. Wan, T. Warwick, R.P. Wells, R.B. Wilcox, S. Zimmermann, M.S. Zolotorev
    LBNL, Berkeley, California, USA
  • C. Adolphsen, K.L.F. Bane, Y. Ding, Z. Huang, C.D. Nantista, C.-K. Ng, H.-D. Nuhn, C.H. Rivetta, G.V. Stupakov
    SLAC, Menlo Park, California, USA
  • D. Arenius, G. Neil, T. Powers, J.P. Preble
    JLAB, Newport News, Virginia, USA
  • C.M. Ginsburg, R.D. Kephart, A.L. Klebaner, T.J. Peterson, A.I. Sukhanov
    Fermilab, Batavia, USA
 
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
The NGLS collaboration is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately 1 MHz. The CW superconducting linear accelerator design is based on developments of TESLA and ILC technology, and is supplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ~100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from femtoseconds and shorter, to hundreds of femtoseconds. In this paper we describe current design concepts, and progress in R&D activities.
 
slides icon Slides TUOCNO05 [5.982 MB]  
 
TUPSO52 R&D Towards a Delta-type Undulator for the LCLS 348
 
  • H.-D. Nuhn, S.D. Anderson, G.B. Bowden, Y. Ding, G.L. Gassner, Z. Huang, E.M. Kraft, Yu.I. Levashov, F. Peters, F.E. Reese, J.J. Welch, Z.R. Wolf, J. Wu
    SLAC, Menlo Park, California, USA
  • A.B. Temnykh
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The LCLS generates linearly polarized, intense, high brightness x-ray pulses from planar fixed-gap undulators. While the fixed-gap design supports a very successful and tightly controlled alignment concept, it provides only limited taper capability (up to 1% through canted pole and horizontal position adjustability) and lacks polarization control. The latter is of great importance for soft x-ray experiments. A new compact undulator design (Delta) has been developed and tested with a 30-cm-long in-vacuum prototype at Cornell University, which adds those missing properties to the LCLS undulator design and is readily adapted to the LCLS alignment concept. Tuning Delta undulators within tight, FEL type tolerances is a challenge due to the fact that the magnetic axis and the magnet blocks are not easily accessible for measurements and tuning in the fully assembled state. An R&D project is underway to install a 3.2-m long out-of-vacuum device in place of the last LCLS undulator, to provide controllable levels of polarized radiation and to develop measurement and tuning techniques to achieve x-ray FEL type tolerances. Presently, the installation of the device is scheduled for August 2013.  
 
WEOCNO03 3-D Theory of a High Gain Free-Electron Laser Based on a Transverse Gradient Undulator 481
 
  • P. Baxevanis, Y. Ding, Z. Huang, R.D. Ruth
    SLAC, Menlo Park, California, USA
 
  The performance of a free-electron laser (FEL) depends significantly on the various parameters of the driving electron beam. In particular, a large energy spread in the beam results in a great reduction of the FEL gain, an effect which is relevant when one considers FELs driven by plasma accelerators or storage rings. For such cases, one possible solution is to use a transverse gradient undulator (TGU) [*,**]. In this concept, the energy spread problem is mitigated by properly dispersing the e-beam and introducing a linear, transverse field dependence in the undulator. This paper presents a self-consistent theoretical analysis of a TGU-based high gain FEL, taking into account three-dimensional (3-D) effects and beam size variations along the undulator [***]. The results of our theory compare favorably with simulation and are used in fast optimization studies of various X-ray FEL configurations.
*T. Smith et al., J. Appl. Phys. 50, 4580 (1979).
**Z. Huang, Y. Ding, C. Schroeder, Phys. Rev. Lett. 109, 204801 (2012).
***P. Baxevanis, R. Ruth, Z. Huang, Phys. Rev. ST-AB 16, 010705 (2013).
 
slides icon Slides WEOCNO03 [3.217 MB]  
 
WEPSO09 Two-Color Self-seeding and Scanning the Energy of Seeded Beams at LCLS 514
 
  • F.-J. Decker, Y. Ding, Y. Feng, M. Gibbs, J.B. Hastings, Z. Huang, H. Lemke, A.A. Lutman, A. Marinelli, A. Robert, J.L. Turner, J.J. Welch, D.H. Zhang, D. Zhu
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) produces typically SASE FEL pulses with an intensity of up to 5 mJ and at high photon energy a spread of 0.2% (FWHM). Self seeding with a diamond crystal reduces the energy spread by a factor of 10 to 40. The range depends on which Bragg reflection is used, or the special setup of the electron beam like over-compression. The peak intensity level is lower by a factor of about five, giving the seeded beam an advantage of about 2.5 in average intensity over the use of a monochromator with SASE. Some experiments want to scan the photon energy, which requires that the crystal angle be carefully tracked. At certain energies and crystal angles different lines are crossing which allows seeding at two or even three different colors inside the bandwidth of the SASE pulse. Out-off plane lines come in pairs, like [1 -1 1] and [-1 1 1], which can be split by using the yaw angle adjustments of the crystal, allowing a two-color seeding for all energies above 4.83 keV.
 
 
WEPSO10 Increased Stability Requirements for Seeded Beams at LCLS 518
 
  • F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.
 
 
WEPSO11 Coherent X-Ray Seeding Source for Driving FELs 522
 
  • A. Novokhatski, F.-J. Decker, R.O. Hettel, Z. Huang, H.-D. Nuhn, M.K. Sullivan
    SLAC, Menlo Park, California, USA
 
  Funding: "Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515
The success of the hard X-ray self-seeding experiment at the LCLS is very important in that it provided narrow, nearly transform-limited bandwidth from the FEL, fulfilling a beam quality requirement for experimental applications requiring highly monochromatic X-rays. Yet, because the HXRSS signal is generated random spikes of noise, it is not a truly continuous monochromatic seed signal and even higher FEL performance would be achieved using a continuous seed source. We propose developing such a source using an X-ray cavity to achieve a continuous, narrow band X-ray seed signal. This cavity consists of four crystals with corresponding Bragg angles of about 45 degrees for each. We will analyze and the interaction of X-rays and electron beams with this cavity. This source uses a train of electron bunches initially accelerated in a linear accelerator which then pass through a radiator element situated within an X-ray cavity. The number of bunches is proportional to the achievable Q-value of the X-ray cavity and may be in the range of 10-100. We do not need a high output power of X-ray beams, which leads to relaxed electron beam requirements. We will consider several options.
 
 
WEPSO27 Recent LCLS Performance From 250 to 500 eV 554
 
  • R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou
    SLAC, Menlo Park, California, USA
  • P. Emma
    LBNL, Berkeley, California, USA
  • R. Soufli
    LLNL, Livermore, California, USA
 
  Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES.
The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV.
[1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho-
ton. 4(9), 641–647 (2010).
 
 
WEPSO53 Harmonic Lasing at the LCLS 623
 
  • D.F. Ratner, Z. Huang, P.A. Montanez
    SLAC, Menlo Park, California, USA
  • E. Allaria
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • W.M. Fawley, L.N. Rodes
    LBNL, Berkeley, California, USA
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Funding: Department of Energy
The LCLS beamlines deliver X-rays to users at photon energies up to 24 keV. With the fundamental wavelength limited to around 10 keV, there is user interest in the third harmonic, which can reach a few percent of the total beam power. McNeil et al* and Schneidmiller and Yurkov** have showed that introducing phase shifts or attenuators into the undulator line can increase harmonic power by driving lasing at the third harmonic. With the development of self-seeding chicanes, LCLS is now in position for a proof-of-principle experiment. Here we present simulations and plans for an experimental test following commissioning of the Soft X-ray Self-Seeding system.
*B.W.J. McNeil, G.R.M. Robb, M.W. Poole and N.R. Thompson, Phys. Rev. Lett., 96 084801 (2006)
**E. Schneidmiller and M. Yurkov, PR-STAB, 14 080702 (2012)
 
 
THOANO03
Experimental Characterization of the Laser Heater Effects on a Seeded FEL  
 
  • E. Ferrari, E. Allaria, W.M. Fawley, L. Giannessi, G. Penco, S. Spampinati
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • W.M. Fawley
    LBNL, Berkeley, California, USA
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • Z. Huang
    SLAC, Menlo Park, California, USA
 
  High brightness electron beams necessary for high gain FEL usually require a laser heater in order to increase the local energy spread in the low energy part of the machine that can mitigate the microbunching instabilities developing in the compressors and in the rest of the linac. Microbunching suppression is essential for FEL operations both in SASE and in seeded mode since it can strongly affect the final electron beam properties. In the case of HGHG, due to the seeding mechanism, the FEL process is extremely sensitive to the amount of energy spread at the undulator entrance, and the FEL output may depend to the amount of heating. In this work we characterize the dependence of the FEL output as a function of the laser heater intensity in the case of FERMI FEL-1. Results also show that for a non Gaussian distribution of the electron beam energy the HGHG may produce significant radiation with an energy spread significantly higher than what expected for a simple Gaussian distribution.  
slides icon Slides THOANO03 [2.333 MB]  
 
THOBNO02 Transverse Gradient Undulators for a Storage Ring X-ray FEL Oscillator 740
 
  • R.R. Lindberg, K.-J. Kim
    ANL, Argonne, USA
  • Y. Cai, Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Dept.~of Energy, Office of Basic Energy Sciences, Contract No.~DE-AC02-06CH11357.
An x-ray FEL oscillator (XFELO) is a fully coherent 4th generation source with complementary scientific applications to those based on self-amplified spontaneous emission*. While the naturally high repetition rate, intrinsic stability, and very small emittance produced by an ultimate storage ring (USR) makes it a potential candidate to drive an XFELO, the energy spread is typically an order of magnitude too large for sufficient gain. On the other hand, Smith and coworkers** showed how the energy spread requirement can be effectively mitigated with a transverse gradient undulator (TGU): since the TGU has a field strength that varies with transverse position, by properly correlating the electron energy with transverse position one can approximately satisfy the FEL resonance condition for all electrons. Motivated by recent work in the high-gain regime***, we investigate the utility of a TGU for low gain FELs at x-ray wavelengths. We find that a TGU may make an XFELO realizable in the largest ultimate storage rings now under consideration (e.g., in either the old Tevatron or PEP-II tunnel).
* K.-J. Kim, Y. Shvyd'ko and S. Reiche, PRL 100 244802 (2008).
** T. Smith, et al., J. Appl. Phys. 50, 4580 (1979).
*** Z. Huang, Y. Ding, and C.B. Schroeder, PRL 109, 204801 (2012).
 
slides icon Slides THOBNO02 [1.208 MB]