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Choi, J.

 
Paper Title Page
TUZH102 Ion Instability Issues in Electron Rings 79
 
  • T.-Y. Lee, J. Choi, H.-S. Kang
    PAL, Pohang, Kyungbuk
  
  The fast ion instability (FII) attracts interests recently for the International Linear Collider Project. FII was found by simulation in SLAC and later observed experimentally. Brief introduction and history of FII is given in this talk and a recent observation of FII in the PLS in-vacuum undulator is reported.  
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WEPMA050 BPM (Beam Position Monitor) in the PAL Linac and BTL 393
 
  • S.-C. Kim, J. Choi, Y. J. Han, J. Y. Huang, D. T. Kim, W. W. Lee, H. J. Park
    PAL, Pohang, Kyungbuk
  
  In Aug. 2004, thirteen BPMs are installed at BTL (Beam Transport Line), and later in Aug. 2005, three BPM installed at main linac for beam trajectory measurement and feedback. BPMs for the BTL consist of 100mm strip-line electrodes in 150mm long chamber and uses SMA-R type feed-throughs. BPMs of the Linac consist of 57mm strip-line electrodes in 100mm short chamber and SMA-R type feed-throughs. 500MHz log-ratio signal processing circuits are used for the Linac and BTL BPM electronics. BPM data acquisition system is developed as an EPICS IOC by using NI S-series DAQ board and NI LabView 7.1. Best read-out accuracy of BPM system is measured as 20mm including BPM electronics. In this paper, we describe on the status of the BPM and its characteristics for PAL Linac and BTL.  
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.  
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.

 
THPMA024 Implementation of High Precision Magnet Power Supply using the DSP 666
 
  • K.-H. Park, J. Choi, C. W. Chung, S.-H. Jeong, D. E. Kim
    PAL, Pohang, Kyungbuk
  • B.-K. Kang
    POSTECH, Pohang, Kyungbuk
  
  This paper presents the precision magnet power supply for the Pohang Light Source using the digitally controlled PWM method. The required current to energize the some magnets was 600 A with the high precision of ~10ppm at least to accomplish a high stable beam operation. This power supply has been implemented using a digital signal processor, TMS320F28 series from Texas Instruments, with high speed external 16-bit ADCs. The designed digital controller includes both a current feedback loop and a DC link voltage feed-forward loop, which was applied by the PI control scheme. To reduce the output current ripple, the damped L-C filter was fabricated at both the DC link and load sides. Various experimental results such as stability, bandwidth and harmonic analysis, as well as simulation are given to verify the characteristics of the DSP based magnet power supply.  
THPMA047 Stair Current Output Power Supply for Switching Magnet 691
 
  • S.-H. Jeong, J. Choi, H.-S. Kang, D. E. Kim, K.-H. Park
    PAL, Pohang, Kyungbuk
  
  The switching magnet for beam distribution to 5 beamlines of 20-MeV PEFP is served with DSP-controlled PWM switching-mode converter. This converter is employed IGBT module and a DSP (Digital Signal Processor) that is operated at ?350A, 2.5 Hz stair output. Current feedback and input voltage feed-forward control schemes are applied to improve the output current stability. Designed filter result in the good stability of each stair. Simulation and experimental results show that the implemented converter achieves stable repeat response at each stair and feasibility for versatile power supply.