Author: Maxwell, T.J.
Paper Title Page
TUB03 FEL Overcompression in the LCLS 337
  • J.L. Turner, F.-J. Decker, Y. Ding, Z. Huang, R.H. Iverson, J. Krzywinski, H. Loos, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, F. Zhou
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
Overcompression of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center is studied. The studies and operational implications are summarized in this talk.
slides icon Slides TUB03 [4.493 MB]  
TUP035 Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS 465
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • Z. Huang, A. Lutmann, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner
    SLAC, Menlo Park, California, USA
  Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515
A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes.
* Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013).
** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013).
Soft X-ray Self-seeding Setup and Results at LCLS  
  • D.F. Ratner, J.W. Amann, D.K. Bohler, M. Boyes, D. Cocco, F.-J. Decker, Y. Ding, D. Fairley, Y. Feng, J.B. Hastings, P.A. Heimann, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, G. Marcus, A. Marinelli, T.J. Maxwell, S.P. Moeller, P.A. Montanez, D.S. Morton, H.-D. Nuhn, D.R. Walz, J.J. Welch, J. Wu
    SLAC, Menlo Park, California, USA
  • K. Chow, L.N. Rodes
    LBNL, Berkeley, California, USA
  • U. Flechsig
    PSI, Villigen PSI, Switzerland
  • S. Serkez
    DESY, Hamburg, Germany
  The soft X-ray self seeding program was designed to provide near transform-limited pulses in the range of 500 eV to 1000 eV. The project was a three-way collaboration between SLAC, Lawrence Berkeley National Lab, and the Paul Scherrer Institute in Switzerland. Installation finished in the Fall of 2013, and after the early stages of commissioning we have measured up to 0.5mJ pulse energy and resolving powers of up to 5000 across the design wavelength range, representing a several-fold increase in the brightness compared to the normal LCLS operating mode. Future work will aim to increase the total pulse energy and establish self-seeding as a robust user operation mode.  
slides icon Slides TUC02 [10.464 MB]  
THB04 Electron Beam Diagnostics and Feedback for the LCLS-II 666
  • J.C. Frisch, P. Emma, A.S. Fisher, P. Krejcik, H. Loos, T.J. Maxwell, T.O. Raubenheimer, S.R. Smith
    SLAC, Menlo Park, California, USA
  Funding: work supported by DOE contract DE-AC02-76-SF00515
The LCLSII is a CW superconducting accelerator driven, hard and soft X-ray Free Electron Laser which is planned to be constructed at SLAC. It will operate with a variety of beam modes from single shot to approximately 1 MHz CW at bunch charges from 10pc to 300pC with average beam powers up to 1.2 MW. A variety of types of beam instrumentation will be used, including stripline and cavity BPMS, fluorescent and OTR based beam profile monitors, fast wire scanners and transverse deflection cavities. The beam diagnostics system is designed to allow tuning and continuous measurement of beam parameters, and to provide signals for fast beam feedbacks.
slides icon Slides THB04 [1.501 MB]  
THP025 Linear Accelerator Design for the LCLS-II FEL Facility 743
  • P. Emma, J.C. Frisch, Z. Huang, H. Loos, A. Marinelli, T.J. Maxwell, Y. Nosochkov, T.O. Raubenheimer, L. Wang, J.J. Welch, M. Woodley
    SLAC, Menlo Park, California, USA
  • J. Qiang, M. Venturini
    LBNL, Berkeley, California, USA
  • A. Saini, N. Solyak
    Fermilab, Batavia, Illinois, USA
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
The LCLS-II is an FEL facility proposed in response to the July 2013 BESAC advisory committee, which recommended the construction of a new FEL light source with a high-repetition rate and a broad photon energy range from 0.2 keV to at least 5 keV. A new CW 4-GeV electron linac is being designed to meet this need, using a superconducting (SC) L-band (1.3 GHz) linear accelerator capable of operating with a continuous bunch repetition rate up to 1 MHz at ~16 MV/m. This new 700-m linac is to be built at SLAC in the existing tunnel, making use of existing facilities and providing two separate FELs, preserving the operation of the existing FEL, which can be fed from either the existing copper or the new SC linac. We briefly describe the acceleration, bunch compression, beam transport, beam switching, and electron beam diagnostics. The high-power and low-level RF, and cryogenic systems are described elsewhere.
poster icon Poster THP025 [0.627 MB]  
THP026 Design Study of LCLS Chirp-Control with a Corrugated Structure 748
  • Z. Zhang, K.L.F. Bane, Y. Ding, Z. Huang, R.H. Iverson, T.J. Maxwell, G.V. Stupakov, L. Wang
    SLAC, Menlo Park, California, USA
  • P. Frigola, M.A. Harrison, M. Ruelas
    RadiaBeam, Marina del Rey, California, USA
  The purpose of this paper is to investigate the use of flat metallic plates with small corrugations as a passive dechirper, studying its effects on beam dynamics. Similar systems have been tested in Pohang and Brookhaven at relatively low energies (~100 MeV) and with relatively long bunches (>1ps) [*,**]. Four meters of such a structure are being machined by Radiabeam Systems for use in the LCLS with a high energy and femtosecond electron beam. In this paper we use a field matching program to obtain the longitudinal and transverse wakes for the purpose of the LCLS dechirper design. In addition, we fit the longitudinal wake to simple functions, so that one can obtain the wake without resorting to the field matching program. Since the transverse wakes–both dipole and quadrupole wakes–are strong, we include beam dynamics simulations to find the tolerances for injection jitter and misalignment in the LCLS.
* P. Emma, et al. PRL 112, 034801
** M. Harrison, et al., NaPAc 2013, Pasadena, USA
THP033 Mechanical Design for a Corrugated Plate Dechirper System for LCLS 785
  • M.A. Harrison, P. Frigola, D.W. Martin, A.Y. Murokh, M. Ruelas
    RadiaBeam Systems, Santa Monica, California, USA
  • Z. Huang, R.H. Iverson, T.J. Maxwell, Z. Zhang
    SLAC, Menlo Park, California, USA
  Funding: This work is supported by Department of Energy grant number DE-SC0009550.
RadiaBeam Systems is developing a novel passive chirp removal system using corrugated plates as studied by Bane and Stupakov.* Following on from low-energy experiments at BNL-ATF,** RBS will install a much larger and powerful system for removing the chirp from the 3-GeV beams in the LTU section at LCLS. The larger plates will present new challenges in the areas of manufacturing and mechanical control. In this paper we review the requirements for the dimensions of the corrugated plates for proper operation and the infrastructure necessary for precisely placing the plates so as not to adversely disrupt the beam.
* K. Bane, et al "Corrugated Pipe as a Beam Dechirper," SLAC-PUB-14925, 2012
** Harrison, M., et al "Removal of Residual Chirp in Compressed Beams Using a Passive Wakefield Technique." NaPAC13, 2013
Prospects of Stimulated X-ray Raman Scattering with Free-Electron Laser Sources  
  • N. Rohringer, V. Kimberg, C. Weninger
    Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
  • M. Agaker, R. Feifel, M. Mucke, J. Nordgren, J.E. Rubensson, C. Sathe, R. Squibb, V. Zhaunerchyk
    Uppsala University, Uppsala, Sweden
  • C. Bostedt, J.D. Bozek, S. Carron Montero, R.N. Coffee, J. Krzywinski, A. Lindahl, A. Lutmann, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • B. Erk, D. Rolles
    DESY, Hamburg, Germany
  • M. Ilchen
    XFEL. EU, Hamburg, Germany
  • T. Kierspel, J. Küpper, T.G. Mullins
    University of Hamburg, Hamburg, Germany
  • O.D. Mücke
    CFEL, Hamburg, Germany
  • M. Purvis, J.J. Rocca, D.P. Ryan
    CSU, Fort Collins, Colorado, USA
  • A. Sanchez-Gonzalez
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  XFELs might open the pathway to transfer non-linear spectroscopic techniques to the x-ray domain, to study electron motion at unprecedented time and length scales. A promising x-ray pump probe technique is based on stimulated electronic x-ray Raman scattering. I will present the first experimental demonstration of stimulated electronic x-ray Raman scattering in a gas sample of neon*. Despite the limited spectral coherence of SASE XFELs, high-resolution spectra can be obtained by statistical methods, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules** and the results of a recent experiment in CO will be discussed. The high-gain regime, involving exponential amplification and strong-field effects will be contrasted to stimulated scattering at moderate x-ray intensities, more appropriate for spectroscopic studies. A critically assessment of the feasibility of nonlinear x-ray spectroscopic techniques and requirements on the stability and pulse parameters of XFEL sources that could enable these new techniques, will be presented.
* C. Weninger et al., Phys. Rev. Lett. 111, 233902 (2013)
** C. Weninger and N. Rohringer, Phys Rev A 88, 053421 (2013)
slides icon Slides FRA01 [3.771 MB]