SLAC, Menlo Park, California, USA
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.
SLAC, Menlo Park, California, USA
End Station A Test Beam (ESTB) is a test beam line at SLAC in the large End Station A (ESA) experimental hall. It uses a fraction of the bunches of the 14.7 GeV electron beam from the Linac Coherent Light Source (LCLS). ESTB provides a unique test beam for particle and particle astrophysics detector research, accelerator instrumentation and accelerator R&D, development of radiation-hard detectors, and material damage studies. It has exceptionally clean and well-defined secondary electron beams, a huge experimental area and good existing conventional facilities. Recently, a new kicker magnet has been installed to divert 5 Hz of the LCLS low energy beam into the A-line. The full installation will include 4 kicker magnets to allow diversion of high energy beams. A new beam dump and a new Personnel Protection System (PPS) have been built in ESA. In stage II, a secondary hadron target will be able to produce pions up to about 12 GeV/c at 1 particle/pulse. This paper reports the progress on ESTB construction and commissioning.
SLAC, Menlo Park, California, USA
Stanford University, Stanford, California, USA
Tech-X, Boulder, Colorado, USA
Purdue University, West Lafayette, Indiana, USA
WEYB02
SLAC, Menlo Park, California, USA
ANL, Argonne, USA
TISNCM, Troitsk, Russia
We report on experimental results of FEL self-seeding with Angstrom wavelengths at the Linac Coherent Light Source (LCLS) at SLAC. The scheme, suggested at DESY*, replaces the 16th 4-m long undulator segment (out of 33 total) with a weak magnetic chicane and a diamond-based monochromator in Bragg transmission geometry. The monochromatized SASE FEL pulse from the first half of the undulator line then seeds the second half. This demonstration of hard x-ray self-seeding is shown to narrow the FEL bandwidth by a factor 40-50, allows longitudinally coherent x-ray pulses near the Fourier-transform limit, and may eventually allow an increases in peak brightness by 1-2 orders of magnitude after applying an aggressive undulator field taper.
* G. Geloni, V. Kocharyan, E. Saldin, DESY 10-133, Aug. 2010.
SLAC, Menlo Park, California, USA
UCLA, Los Angeles, California, USA
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).