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Jeong, Y. U.

Paper Title Page
MOPPH027 Status of the KAERI THz FEL for the Application on Security Inspection  
 
  • P. Ahn, H. J. Cha, B. C. Lee, J. Mun, S. H. Park, Y. U. Jeong
    KAERI, Daejon
  • G. M. Kazakevich
    Fermilab, Batavia, Illinois
  
  Terahertz (THz) technology has been considered as a new tool for security inspection due to its safe energy range to human irradiation, foot-print spectral characteristics for most chemicals and bio-materials, and relatively high spatial resolution for imaging. One of the main tasks in the THz inspection technology is to develop a high power and compact source to realize a real-time imaging. We have developed a compact terahertz (THz) free electron laser (FEL). The FEL operates in the wavelength range of 100–1200 micrometers, which corresponds to 0.3–3 THz. THz radiation from the FEL shows much higher power of 100 W when compared to the power level, < 100 mW, of the table-top sources by conventional lasers. The THz FEL beam shows a good performance in pulse-energy stability, polarization, spectrum and spatial distribution. We report the experimental studies of the transmission and reflection-type scanning imaging of baggage and a window dummy. The required power level of the THz sources is estimated for the practical applications of the inspection imaging.  
MOPPH033 Diffraction Optical Elements and Optical Systems with a High Power Monochromatic Terahertz Source 93
 
  • H. J. Cha, Y. U. Jeong
    KAERI, Daejon
  • V. S. Cherkassky, L. A. Merzhievsky, S. A. Zhigach
    NSU, Novosibirsk
  • A. V. Fanova, B. A. Knyazev, G. N. Kulipanov, N. Vinokurov, I. A. Polskikh
    BINP SB RAS, Novosibirsk
  
  We have developed reflective diffraction optical elements (DOE) for focusing radiation of terahertz free electron lasers (FEL). Metal-dielectric Fresnel zone plates and metallic kinoform "lenses" were fabricated and tested using FEL radiation. A microbolometer camera (see the paper by Esaev et al. at this conference) sensitive to THz radiation had been applied for recording both terahertz beam caustic and terahertz images. Diffraction efficiency of a kinoform lens appears to be about unity. Quality of images obtained with the kinoform lens was studied. The lens was used as a key element for a Toepler optical system, which were used for studying condense matter non-uniformities and deformations. The experiments were performed at Novosibirsk and KAERI FELs.  
MOPPH039 Sideband Instability in a Compact THz Free-Electron Laser at KAERI  
 
  • P. Ahn, H. J. Cha, B. C. Lee, J. Mun, S. H. Park, Y. U. Jeong
    KAERI, Daejon
  • G. M. Kazakevich
    Fermilab, Batavia, Illinois
  
  Frequency offset of a Sideband instability has been observed in a compact waveguide-mode terahertz (THz) free-electron laser (FEL). The spectra of the FEL pulses were measured by a Fabry-Perot spectrometer having a resolution of 10(-4) of the central wavelength at a 2-3 THz range. The shift of the sideband was measured to be 0.5-1.2 micrometers depending on the FEL wavelength from 110 to 165 micrometers. An increase of the sideband shift for a longer wavelength can be explained by the change of the wave’s group velocity in a plane-parallel waveguide. Mode competition between the sidebands and primary wave was observed by changing the cavity length of the FEL. We could decrease the number of the modes and reduce the linewidth of the spectra by controlling the cavity detuning. We have discussed the complexity of the sideband instability depending on the FEL wavelengths and its gain characteristics.  
MOPPH064 A Project of SC ERL at KAERI 160
 
  • Y. H. Han, Y. U. Jeong, B. C. Lee, S. H. Park
    KAERI, Daejon
  • S. V. Miginsky, A. V. Bondarenko
    BINP SB RAS, Novosibirsk
  
  A project of an ERL at Korea Atomic Energy Research Institute is described. The ERL will be connected to the existing machine without any modification. It consists of two 180° bents and two straight sections: one is for an FEL, another for a Compton X-ray source. One can choose the regime controlling the lenses. The total ERL is isochronous to avoid any problem with longitudinal beam instability. It will be possible to control both Sx and Sy transormation matrix elements independently to suppress longitudinal beam instability and allow the increase of beam current. Sextuples will be installed in bents to suppress chromatic aberration. This design provides operation in FEL regime with high electron efficiency in the range of electron energies 12–22 MeV.