polarization

Paper	Title	Other Keywords	Page
MOPPH010	Three-Dimensional Analysis of the Surface Mode Supported by a Reflection Grating	electron, electromagnetic-fields, laser, free-electron-laser	38
	K.-J. Kim ANL, Argonne, Illinois V. Kumar RRCAT, Indore (M. P.)
	In a Smith-Purcell Free-Electron Laser (SP-FEL), the electron beam interacts with the surface mode supported by a metallic reflection grating to produce coherent radiation. All the previous analyses of SP-FEL had considered the localization of the surface mode only in the direction perpendicular to the grating surface and assumed translational invariance along the direction of grooves of the grating. In this paper, we include the localization of the surface mode along the direction of grooves and study the three-dimensional structure of the surface mode in order to include diffraction effects in the analysis of SP-FELs. Full three-dimensional Maxwell-Lorentz equations are derived for the self-consistent nonlinear analysis of SP-FELs.
MOPPH040	A Study of Detection Schemes in Electro-Optic Sampling Technique	laser, electron, diagnostics, background	101
	J. Y. Huang, C. Kim, I. S. Ko, Y. W. Parc PAL, Pohang, Kyungbuk
	Electro-Optic Sampling (EOS) is the ingenious tool for the measurement of the electron beam or Thz radiation. There are two traditional detection schemes: one is the crossed polarizer scheme and another is balanced detection one. A new detection scheme called Near Crossed Polarizer scheme in the EOS technique is developed to increase the Signal to Noise Ratio in the experiment. The new detection scheme is studied in detail and the 3D scanning result with electron beam in FLASH is compared with the detection scheme. The new detection scheme has an analytical problem which shows two solutions for the relative phase shift for specific measurement of the electron beam. That problem is also studied through the comparative study between simulation and the analyzed data from the TEO setup in FLASH.
WEBAU04	Single-Shot Longitudinal Bunch Profile Measurements at FLASH Using Electro-Optic Detection: Experiment, Simulation, and Validation	laser, electron, simulation, linac	310
	V. R. Arsov, E.-A. Knabbe, B. Schmidt, P. Schmüser, B. Steffen DESY, Hamburg G. Berden, A. F.G. van der Meer FOM Rijnhuizen, Nieuwegein W. A. Gillespie, P. J. Phillips University of Dundee, Nethergate, Dundee, Scotland S. P. Jamison STFC/DL/ASTeC, Daresbury, Warrington, Cheshire A. MacLeod UAD, Dundee
	At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment for single shot, non-destructive measurements of the longitudinal electric charge distribution of individual electron bunches. The profile of the electric bunch field is electro-optically encoded onto a stretched Ti:Sa laser pulse. In the decoding step, the profile is retrieved from a cross-correlation of the encoded pulse with a 35 fs laser pulse, obtained from the same laser. At FLASH, sub-100 fs electron bunches have been measured during FEL operation with a resolution of better than 50 fs. The electro-optic encoding process in gallium phosphide as well as the decoding step in a frequency doubling BBO crystal were numerically simulated using bunch shapes simultaneously measured with a transverse-deflecting rf structure as input data. In this contribution, we present electro-optically measured profiles and compare them with the simulation.
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WEPPH022	Feasibility Test of Shottoky Effect-Gated Photocathode RF Gun	laser, cathode, gun, focusing	382
	M. Kobayashi Nanophoton corporation, Osaka H. T. Tomizawa JASRI/SPring-8, Hyogo-ken
	We proposed Shottoky effect-gated photocathode RF gun using z-polarization of laser source. Radically polarized laser propagation modes exist theoretically and were recently generated practically. Focusing a radically polarized beam on the photocathode, the z-polarization of laser is generated at the focusing point. The generated Z-polarization can exceed an electrical field of 1GV/m easily with fundamental wavelength from compact femtosecond laser systems. According to our calculations, the z-field of 1GV/m needs 100MW at peak power for fundamental wavelength (790nm) and 25MW for SHG. In the field of 1GV/m, the work function of copper cathode reduces ~2 eV. The quantum efficiency will be ~10-4 at SHG by the Shottoky effect associated with the 1GV/m. This Shottky effect can be used as a gate of photo-emission process. In our design of Shottoky effect-gated Photocathode, the fundamental is used as gate pulse and SHG as laser source for photo-emission process. The same single laser pulse can also gate its emission by itself. To keep normal incidence on the cathode, we developed modified-Cessegrain-type incident optics combining with axicon lens pair. In the first test run, we are preparing z-polarizer for SHG to generate radial and azimuth polarizations. Comparing photo-emission process with these polarizations, we make clear the feasibility of this new concept of photocathode.
WEPPH053	Non-Destructive Single-Shot 3-D Electron Bunch Monitor with Femtosecond-Timing All-Optical System for Pump & Probe Experiments	laser, electron, multipole, optics	472
	H. Hanaki, H. T. Tomizawa JASRI/SPring-8, Hyogo-ken T. Ishikawa RIKEN Spring-8 Harima, Hyogo
	We are developing a 3-D electron bunch monitor based on EO sampling, using yearlong stable femtosecond laser source of SPring-8 RF gun. Our developing single-shot bunch monitor can characterize the 3-D (both longitudinal (1D) and transverse (2D)) distribution and position of an electron bunch with femtosecond resolution. This non-destructive monitor can be used as an electron energy chirping monitor in a dispersive region for X-FEL commissioning. The probe laser for spectral decoding EO sampling is prepared as radically polarized and completely linearly chirped broad-bandwidth (~500nm) supercontinuum. EO-probe is made of 8 EO-crystals with assembling each EO-optical axes along radial beam axes. The probe lineally chirped laser is longitudinally sifted in 8 transverse sectors for spectral decoding. We are planning to use organic polymer film as a femtosecond resolution EO-probe instead of crystals. This 3-D bunch monitor with spectrograph detects and analyzes the wake filed of electron bunches as longitudinally spectral decoding and transversely multi-pole expansion. In addition, we are developing all-optical system for femtosecond-timing pump & probe experiments. The EO-sampled probe laser pulse will use as a femtosecond-timing signal pulse. This signal pulse is amplified with a NOPA (noncollinear optical parametric amplifier), using an SHG of Yb fiber laser as a pump laser.
THBAU04	Millimeter Waves Sensing Behind Walls - Feasibility Study with FEL Radiation	radiation, controls, coupling, survey	501
	M. Einat, M. Kanter, B. Litvak, A. Yahalom, B. Yu. Kapilevich CJS, Ariel A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
	The existing through-wall imaging (TWI) systems operate in 1 – 10 GHz, basically, in order to reduce an attenuation caused by building material. However, the spatial resolution is drastically degraded when the operating frequency is relatively low. On the other hand, a majority of building materials demonstrate increased losses as the frequency increases. As a result, higher RF power from the source is required. The Israeli mm-wave FEL provides unique opportunity to solve the above TWI problem permitting to deliver output power 100-1000W at 85-105 GHz. Design of TWI system operating on mm-waves needs comprehensive study of constitutive parameters of different building materials. This paper describes systematic measurements of effective attenuation constant of typical building materials such as concrete bricks, wood, tiles, sand, gypsum, etc. on mm-waves using powerful FEL radiation. Since the Rayleigh criterion for surface roughness cannot be satisfied for some of measured materials, scattering and depolarization effects lead to increasing measured attenuation in comparison with bulky material. Additional experiments were performed to estimate a contribution of these effects into the measured attenuation.
	Slides