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resonance

Paper Title Other Keywords Page
MOPP055 The Infrared Undulator Project at the VUV-FEL undulator, radiation, electron, diagnostics 183
 
  • O. Grimm, J. Feldhaus, J. Rossbach, E. Saldin, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg
  
 

Funding: University of Hamburg

A special electromagnetic wiggler generating infrared radiation in the range 1-200 microns is planned to be installed at the DESY VUV-FEL in Hamburg by autumn 2006. The device is located after the FEL undulators, using the spent electron beam. The purpose is two-fold: first, it will serve longitudinal electron beam diagnostics, similar to other methods currently investigated using the coherent emission of radiation at wavelengths similar to the bunch length, and second it will be used as a powerful (100 MW peak) source for short (few ps) infrared radiation pulses. The natural, perfect synchronization with the VUV pulses will allow for pump-probe experiments with high timing precision. This paper will give an overview of the project, including the infrared beam transport line.

   
    
TUOA004 Theory of Coherent Radiation from a Grating-Waveguide Free-Electron Laser electron, grating-waveguide, fel, oscillator 239
 
  • Y.-C. Huang, Y.-Y. Lin
    NTHU, Hsinchu
  
 

Funding: Center for Advanced Information System and Electronics Research(CAISER)

A Smith-Purcell radiator produces transversely asymmetric radiation modes due to the arrangement of a grating on one side of the electron beam. This asymmetric output could limit the usefulness of such a device in the THz spectrum where diffraction of waves is severe. It is possible to produce symmetric radiation from a double-grating waveguide driven by an electron beam traversing the waveguide gap. We derive a theory that describes the modes and small signal gain of this novel grating-waveguide free-electron laser. Our theory shows that extremely high laser gain is obtained when the electron beam is phase matched to the middle or edge of the radiation bands where the radiation modes have zero group velocity. In our calculation we obtained 66dB/mm gain at 298 µm for a 5 mA, 30keV driving beam in a grating waveguide with a 50-micron, 40% duty-cycle grating period, a 60-micron groove depth, and a 150 micron waveguide gap. This extremely high gain indicates that this novel device establishes resonance without resonator mirrors in a one-dimensional photonic-crystal lattice or from distributed feedbacks in the grating pairs. Experimental progress will be reported in the conference.