Author: Bae, S.
Paper Title Page
MOP048 A Compact THz FEL at KAERI: the Project and the Status 1
  • S.V. Miginsky, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, K. Lee, J. Mun, S. Setiniyaz
    KAERI, Daejon, Republic of Korea
  • S. H. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
  A new compact THz free electron laser driven by a microtron is being recently developed at KAERI. It uses a hybrid electromagnetic undulator. A novel scheme of injection/extraction/outcoupling is developed. The machine is partially assembled and commissioned. Characteristic features and current state are described in the paper.  
Ultrafast Electron Diffraction Facility Based on an RF Photogun and Achromatic 90-degree Bends for Sub-100-Femtosecond Timing Jitter  
  • Y.U. Jeong, S. Bae, I.H. Baek, B.A. Gudkov, B. Han, K.H. Jang, H.W. Kim, M.H. Kim, Y.-C. Kim, K. Lee, S.V. Miginsky, J. Mun, J.H. Nam, S. Park, S. Setiniyaz
    KAERI, Daejon, Republic of Korea
  • R. Fabian, H. Ihee, J. Kim, K.Y. Oang, H. Yang
    KAIST, Daejeon, Republic of Korea
  • J.H. Han
    PAL, Pohang, Kyungbuk, Republic of Korea
  • H.W. Kim
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • K.W. Kim
    Chung Buk National University, Cheongju, Republic of Korea
  • S.V. Miginsky, N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • S. H. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
  • S. Park
    Kyungpook National University, Daegu, Republic of Korea
  We have developed a laboratory-scale ultrashort electron accelerator for investigating femtosecond dynamics of atoms or molecules with pump-probe experiments. This system includes an S-band radio-frequency (RF) photogun and four achromatic bends for compressing electron bunches. Two of them are for ultrafast electron diffraction (UED) experiments on solid and gas samples. The electron bunch duration at the UED beamlines was designed to be ~30 fs in rms. Our target value of the timing jitter between the pumping laser pulse and probing electron bunch is approximately 10 fs. The synchronization between the pumping laser oscillator and a master oscillator of the RF system was successfully performed with the extremely low timing fluctuation of ~10 fs during 24-hour operation*. We developed a high-intense terahertz pumping source with field strength of more than 0.5 MV/cm for THz-pump and electron-probe experiments. We are conducting three independent application experiments with superconducting and strongly-correlated materials and gas samples for ultrafast molecular dynamics.
* H. Yang et al., "10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources," Scientific Reports, 7, 39966, 2017.
Development of a Hybrid Electromagnetic Planar Undulator Having Horizontal Focusing Force for a Compact THz FEL  
  • S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, K. Lee, S.V. Miginsky, J. Mun, S. Park
    KAERI, Daejon, Republic of Korea
  • M.Y. Jeon
    Chungnam National University, Daejoen, Republic of Korea
  A THz table-top FEL is under development at KAERI for security applications. We developed a compact microtron to accelerate electrons up to 5 MeV with an energy spread of about 0.4%. A hybrid electromagnetic planar undulator was designed and fabricated to cover the FEL's lasing wavelength range of 400~600 μm. The magnetic field strength in the gap of the undulator is changeable from 0.76 to 1.14 T by varying the coil current of the undulator from 1.5 to 2.5 kA. The undulator provides a horizontal focusing force to keep the low energy electrons passing a specially-designed narrow waveguide. The undulator field error of 1st and 2nd integrals, which is 3.61 x 10-4 T·m and 5.75 x 10-5 T·m2, respectively, was minimized to reduce the deflection angle and trajectory offset of electron beam to pass through the waveguide having a width of 10 mm.