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Wang, J.

Paper Title Page
WPAE069 The APS Septum Magnet Power Supplies Upgrade 3795
 
  • B. Deriy, A.L. Hillman, G.S. Sprau, J. Wang
    ANL, Argonne, Illinois
  
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The higher requirements for beam injection stability at the APS storage ring demand improvement of pulsed power supplies for the septum magnets. The upgrade will be performed in two stages. In the first stage we will implement a new power supply circuit with a new regulation timing sequence that will provide better voltage regulation performance. A common design was made for all of the septum magnet power supplies at the APS. The new regulation module has already been tested on both thin and thick septum magnet power supplies. This test showed that the new target for the current regulation stability, 1/2000 with less than 10-ns jitter, is achievable with this approach. In the second stage we will implement an embedded microprocessor system that will provide digitally controlled shot-to-shot current regulation of the power supply. The system comprises modules for communication with EPICS, data acquisition, and precise timing. A prototype has already been built and will also be discussed.

 
WPAE070 Injector Power Supplies Reliability Improvements at the Advanced Photon Source 3804
 
  • A.L. Hillman, S.J. Pasky, N. Sereno, R. Soliday, J. Wang
    ANL, Argonne, Illinois
  
  Funding: *Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

Operational goals for the APS facility include 97% availability and a mean time between unscheduled beam losses (faults) of 70 hours, with more than 5000 user hours of scheduled beam per year. To meet this objective, our focus has changed to maximizing the mean time between faults (MTBF). We have made various hardware and software improvements to better operate and monitor the injector power supply systems. These improvements have been challenging to design and implement in light of the facility operating requirements but are critical to maintaining maximum reliability and availability of beam for user operations. This paper presents actions taken as well as future plans to continue improving injector power supply hardware and software to meet APS user operation goals.

 
TPAE064 Externally Controlled Injection of Electrons by a Laser Pulse in a Laser Wakefield Electron Accelerator 3644
 
  • S.-Y. Chen, C.-L. Chang, W.-T. Chen, T.-Y. Chien, C.-H. Lee, J.-Y. Lin, J. Wang
    IAMS, Taipei
  
  Funding: National Science Council, Taiwan

Spatially and temporally localized injection of electrons is a key element for development of plasma-wave electron accelerator. Here we report the demonstration of two different schemes for electron injection in a self-modulated laser wakefield accelerator (SM-LWFA) by using a laser pulse. In the first scheme, by implementing a copropagating laser prepulse with proper timing, we are able to control the growth of Raman forward scattering and the production of accelerated electrons. We found that the stimulated Raman backward scattering of the prepulse plays the essential role of injecting hot electrons into the fast plasma wave driven by the pump pulse. In the second scheme, by using a transient density ramp we achieve self-injection of electrons in a SM-LWFA with spatial localization. The transient density ramp is produced by a prepulse propagating transversely to drill a density depression channel via ionization and expansion. The same mechanism of injection with comparable efficiency is also demonstrated with a transverse plasma waveguide driven by Coulomb explosion.

 
RPAT059 The SRI Beam Size Monitor Developed at NSRRC 3465
 
  • T.C. Tseng, J.-R. Chen, H.C. Ho, C.-K. Kuan, C.J. Lin, S.Y. Perng, D.-J. Wang, J. Wang
    NSRRC, Hsinchu
  
  A beam size monitor based on the synchrotron radiation interferometer (SRI) was installed in the NSRRC TLS. This monitor consists of a simple diagnostic beamline with a water-cooled beryllium mirror inside and a detecting optical system for both vertical and horizontal beam size measurement. The beam sizes measured are 48 micron and 160 micron respectively and are more close to the theoretical values than the synchrotron image monitor. Comparing with other monitors, at least 1 micron beam size variation is detectable. To minimize the thermal effect, the mirror is located far away from the source point and closed to the detecting optical system. The thermal distortion of the mirror is quite small measured by a portable long trace profiler (LTP) and agrees with the simulating analysis. The detailed monitor system design and testing results are presented in this paper.  
RPPE008 Water Induced Vibration in the NSRRC 1102
 
  • D.-J. Wang, H.C. Ho, Z.-D. Tsai, J. Wang
    NSRRC, Hsinchu
  
  Water flow related vibrations were found on the spectrum of electron beam position monitor in the NSRRC. They were associated with the vibrations of quadrupole magnets. One major vibration source was from a pump in the cooling water system. Most amount of vibration coupled through water pipe and water flow and propagated to the magnets. A small water flow station was set up to study the effect about coupling, propagating and excitation. Some damping schemes tested in the ring to improve the vibration are also included..  
RPAT090 The Study of New Signal Processing Technique in Photon Beam Position Monitors 4239
 
  • S.F. Lin, H. Gao, P. Lu, B. Sun, J. Wang
    USTC/NSRL, Hefei, Anhui
  
  A log-ratio signal processing technique in photon beam position monitors (PBPM) was presented in this paper. The main performances (e.g. sensitivity, position offset and linearity range) of split PBPM and a pair of wires PBPM were analyzed , and the result of the measurement fit well with the theory. An inexpensive logarithmic amplifier chip which can measure photon currents from 0.1nA to 3.5mA was used in electronic circuits. The logarithmic ratio of the signal amplitudes from the PBPM provides a real-time analog signal that has wider linearity range and higher bandwidth than signal processing technique.

Supported by Natural Science Foundation of China (10275062) and CAS Knowledge Innovation Project (KY4206).

 
FPAT072 The Status of HLS Control System 3862
 
  • G. Liu, X. Bao, C. Li, W. Li, J. Wang, Xie. Xie, K. Xuan
    USTC/NSRL, Hefei, Anhui
  • J. Li
    DU/FEL, Durham, North Carolina
  
  HLS (Hefei Light Source) at NSRL (National Synchrotron Radiation Lab) consists of three parts: 200Mev Linac, transport line and 800Mev storage ring. The control system was upgraded based on EPICS (Experimental Physics and Industrial Control system) from 1999 to 2004. This paper will cover the experience of using PC-based hardware under EPICS, data archiving, and some high level tools for physics and operation use.