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Ko, I. 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.  
WEPMA080 Control System for the Bending MPS at PLS Linac 437
 
  • J. H. Kim, J. Choi, K. M. Ha, J. Y. Huang, H.-S. Kang, J. M. Kim, S.-C. Kim, I. S. Ko
    PAL, Pohang, Kyungbuk
  
  The former control system of the bending MPS (Magnet Power Supply) has a three-layered architecture. It was developed by in-house members in early 1993. It is upgraded based on EPICS as the protocol for the full upgrade of the PLS control system. We have replaced the former VME 68K CPU boards with OS-9 to new Power CPU boards operated by VxWorks as IOC in the linac klystron gallery. The upgraded bending MPS control system consists of a MVME5100 EPICS IOC core in the lower level control. It is implemented with the MEDM tool of EPICS to provide friendly Graphical User Interfaces. This paper describes the VME IOC and OPI and embedded local controller in MPS cabinet used for the bending MPS control in the PLS linac

Pohang Accelerator Laboratory, Pohang, 790-784, KoreaThis works supported by the Ministry of Science and Technology, Korea.

 
WEPMA054 Photon Beam Position Monitor with Hydraulic Level System 398
 
  • Y. J. Han, J. Choi, J. Y. Huang, S. N. Kim, Y.-C. Kim
    PAL, Pohang, Kyungbuk
  • I. S. Ko
    POSTECH, Pohang, Kyungbuk
  
  In a synchrotron radiation source like the Pohang Light Source (PLS), a great effort has been made on beam stability improvements. For the beamline user-sided orbit feedback, Photon Beam Position Monitor(PBPM) provides more practical informations on the position and angle of the electron beam at the center of the bending magnet, compared the closed orbit data. For improvement of the orbit stability, PBPMs are used in PLS. However, as the ground of PLS moves about 2mm every year, we also monitor the level difference between the storage ring and the beamline floor with Hydraulic Level System (HLS). The design and experimental results of PBPM with HLS will be presented.  
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.  
THPMA114 Activities on the Nuclear Data Measurement at the Pohang Neutron Facility Based on Electron Linac 800
 
  • G. N. Kim
    Kyungpook National University, Daegu
  • M.-H. Cho, I. S. Ko, W. Namkung
    POSTECH, Pohang, Kyungbuk
  • H.-S. Kang, Y. D. Oh
    PAL, Pohang, Kyungbuk
  
  We report the present status of the Pohang Neutron Facility which consists of an electron linear accelerator, a water-cooled Ta target, and a 12-m time-of-flight path. We measured the neutron total cross-sections in the neutron energy range from 0.1 eV to few hundreds eV by using the neutron time-of-flight method. A 6LiZnS(Ag) glass scintillator was used as a neutron detector. The neutron flight path from the water-cooled Ta target to the neutron detector was 12.1 m. The background level was determined by using notch-filters of Co, In, Ta, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and those from neutron capture, we employed a neutron-gamma separation system based on their different pulse shapes. The present measurements of Ta, Hf, Ag, and Mo samples are in general agreement with the evaluated data in ENDF/B-VI. The resonance parameters were extracted from the transmission data from the SAMMY fitting and compared with the previous ones.