Author: Raubenheimer, T.O.
Paper Title Page
TUEPPB015 Generation of Narrow-Band Coherent Tunable Terahertz Radiation using a Laser-Modulated Electron Beam 1146
  • M.P. Dunning, C. Hast, E. Hemsing, R.K. Jobe, D.J. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, Z.M. Szalata, D.R. Walz, S.P. Weathersby, D. Xiang
    SLAC, Menlo Park, California, USA
  Funding: Work supported by US DOE contract DE-AC02-76SF00515.
The technical layout and initial results of an experiment to generate narrow-band, coherent, tunable terahertz (THz) radiation through the down-conversion of the frequency of optical lasers using a laser-modulated electron beam are described. In this experiment a 120 MeV electron beam is first energy modulated by two lasers with different wavelengths. After passing through a dispersive section, the energy modulation is converted into a density modulation at THz frequencies. This density-modulated beam will be used to generate narrow-band THz radiation using a coherent transition radiator inserted into the beam path. The central frequency of the THz radiation can be tuned by varying the wavelength of one of the two lasers or the energy chirp of the electron beam. The experiment is being performed at the NLCTA at SLAC, and will utilize the existing Echo-7 beamline, where echo-enabled harmonic generation (EEHG) was recently demonstrated.
TUPPC051 FACET Tolerances for Static and Dynamic Misalignment 1284
  • J.T. Frederico, M.J. Hogan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
The Facility for Advanced Accelerator and Experimental Tests (FACET) at the SLAC National Accelerator Laboratory is designed to deliver a beam with a transverse spot size on the order of 10 μm x 10 μm in a new beamline constructed at the two kilometer point of the SLAC linac. Commissioning the beamline requires mitigating alignment errors and their effects, which can be significant and result in spot sizes orders of magnitude larger. Sextupole and quadrupole alignment errors in particular can introduce errors in focusing, steering, and dispersion which can result in spot size growth, beta mismatch, and waist movement. Alignment errors due to static misalignments, mechanical jitter, energy jitter, and other physical processes can be analyzed to determine the level of accuracy and precision that the beamline requires. It is important to recognize these effects and their tolerances in order to deliver a beam as designed.
TUPPP082 Optimization of a Terawatt Free Electron Laser 1780
  • J. Wu, X. Huang, Y. Jiao, A.U. Mandlekar, T.O. Raubenheimer, S. Spampinati, G. Yu
    SLAC, Menlo Park, California, USA
  • P. Chu
    FRIB, East Lansing, Michigan, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
There is great interest in generating a terawatt (TW) hard X-ray free electron laser (FEL) that will enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such pulses was carried out em- ploying a configuration beginning with an SASE amplifier, followed by a "self-seeding" crystal monochromator, and finishing with a long tapered undulator. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A genetic algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LCLS/LCLS-II systems.
WEPPP056 Positron PWFA Simulations for FACET 2834
  • S.J. Gessner, E. Adli, S. Corde, R.J. England, J.T. Frederico, M.J. Hogan, S.Z. Li, M.D. Litos, T.O. Raubenheimer, D.R. Walz, Z. Wu
    SLAC, Menlo Park, California, USA
  • W. An, W.B. Mori
    UCLA, Los Angeles, California, USA
  Funding: Work supported [optional: in part] by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
When a positron beam enters a plasma, plasma electrons are drawn in toward the beam axis, creating a region of extremely large charge density with complicated, nonlinear fields. Few analytic solutions exist to describe these fields, and this necessitates the use of simulations to model positron beam and plasma interactions. This presentation should cover recent work on positron PWFA simulations using the QuickPIC* particle-in-cell code. I will discuss the computational challenges associated with positron PWFA and specific applications of the simulations for future experimental tests at the FACET user facility at SLAC.
* C. Huang et al., "QuickPIC: A highly efficient particle-in-cell code for modeling wakefield acceleration in plasmas," J. Comp. Phys. 217, 658 (2006).