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Oh, J.-S.

Paper Title Page
TUPMA057 Physics Design of PAL-XFEL Undulator 190
 
  • D. E. Kim, C. W. Chung, J.-S. Oh, K.-H. Park
    PAL, Pohang, Kyungbuk
  • I. S. Ko
    POSTECH, Pohang, Kyungbuk
  
  Pohang Accelerator Laboratory(PAL) is planning a 0.3 nm – 0.45 nm SASE (Self Amplification of Spontaneous Emission) XFEL based on 3.7 GeV linear accelerator. It is targeting utilization of 0.1 nm X-ray radiation using the 3rd harmonic FEL radiation. With 3.7 GeV electron beam energy, achieving 0.3 nm fundamental FEL lazing is very challenging and it requires very low emittance electron beam with minimum energy spread. It also requires small period undulator with very small gap. In this context, application of SPring8 type in vacuum undulator is seriously considered. This reflects the experiences from SPring8 SCSS project. In this report, the physics design efforts of the undulator is described. The periodic parts are optimized to achieve the highest field with other requirements. The end structures were designed to be asymmetric along the beam direction to ensure systematic zero 1st field integral. The thickness of the last magnets were adjusted to minimize the transition distance to the fully developed periodic field. The final design features 4 mm minimum pole gap, 15 mm period, peak effective field of 1.09 Tesla.  
WEPMA083 Design of C-band Standing-wave Accelerating Structure 440
 
  • S. H. Kim, M.-H. Cho, W. Namkung, B. Park, H. R. Yang
    POSTECH, Pohang, Kyungbuk
  • S. D. Jang, J.-S. Oh, S. J. Park, Y. G. Son
    PAL, Pohang, Kyungbuk
  
  We design a C-band standing-wave accelerating structure for a compact electron linac. It is capable to produce electron beams with the beam energy of 4 MeV and the pulsed beam current of 50 mA. It is to be operated in the π/2 mode with the on-axis coupled structure. The beamline is composed of the E-gun and the accelerating column with 3 and half bunching cells and 9 and half normal cells. We design standing-wave RF cavities using the OMEGA3P code to implement the asymmetric magnetic coupling slots. For the beam dynamics study, we use the PARMELA code with the SUPERFISH fields configuration. Without the pre-buncher cavity and the focusing magnets, the lost beam power to the wall is 10 kW for the output beam power of 200 kW, while the transmission is 58%.  
THPMA067 Stability Analysis of a Klystron-Modulator for PAL XFEL 729
 
  • J.-S. Oh, C. W. Chung, S. D. Jang, S. J. Kwon, Y. G. Son, J.-H. Suh
    PAL, Pohang, Kyungbuk
  • I. S. Ko, W. Namkung
    POSTECH, Pohang, Kyungbuk
  
  The PAL (Pohang Accelerator Laboratory) is persuading to construct a SASE-XFEL facility (PAL XFEL). The stable electron beam is essential for the single-pass free electron laser facility. The beam stability is governed by an accelerating RF field, of which fluctuation is mainly caused by the modulation of klystron voltage pulses. Therefore, it is directly determined by the charging stability of a modulator that uses an inverter charging system. The stable charging power supply can be realized by a stable probing and correct manipulating of a charging signal, a fine control of charging current, low noise environment, etc. This paper shows the detail analysis of the stability dependency of a klystron-modulator on the related parameters.  
THPMA076 Development of the Klystron Modulator using a High-voltage Inverter Power Supply 743
 
  • Y. G. Son, C. W. Chung, D. E. Kim, S. J. Kwon, J.-S. Oh
    PAL, Pohang, Kyungbuk
  
  The existing klystron modulator in the Linac use a 60 Hz high voltage power supply and adopt traditional L-C resonant charging scheme with De-Qing circuit. The stability of the output high voltage is not satisfactory especially when the AC line voltage fluctuations. If an inverter power supply is used as a HV generator, it will just meet the demands A high frequency inverter switching makes the overall system size small. The command-charging feature can guarantee the high reliability of switching function. In order to increase the stability, operating reliability and comply with the PLC (programming logic controller) and touch screen control system of PLS, an upgrading works is now in progress. This paper will discuss some inverter power supply design considerations and show the test results.  
THPMA127 Development of L-band Electron Accelerator for Irradiation Source 821
 
  • S. H. Kim, M.-H. Cho, S.-I. Moon, W. Namkung, B. Park, H. R. Yang
    POSTECH, Pohang, Kyungbuk
  • S. D. Jang, J.-S. Oh, S. J. Park, Y. G. Son
    PAL, Pohang, Kyungbuk
  
  An intense L-band electron accelerator is under development for irradiation applications. It is capable of producing 10-MeV electron beams of 30 kW with the fully beam-loaded condition. The accelerator is powered by a pulsed klystron of 1.3 GHz and 25 MW with the 60-kW average power. The accelerating column, a traveling-wave structure, is operated with the 2π/3 mode and is installed vertically with other beam-line components. With the beam dynamics simulation, the beam transmission efficiency is over 90% and the beam size is enough to clear the apertures. Design details and the status of installation are presented for the L-band electron accelerator.