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Li, J.

Paper Title Page
MPPP049 Observations and Measurements of Anomalous Hollow Electron Beams in a Storage Ring 3082
 
  • Y.K. Wu, J. Li
    DU/FEL, Durham, North Carolina
  • J. Wu
    SLAC, Menlo Park, California
  
  Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370 and by U.S. DOE grant DE-FG05-91ER40665 (YW and JL). This work is also supported by U.S. DOE contract DE-AC02-76SF00515 (JW).

This paper reports first observations and measurements of anomalous hollow electron beams in a storage ring. In a lattice with a negative chromaticity, hollow electron beams consisting of a solid core beam inside and a large ring beam outside have been created and studied in the Duke storage ring. We report the detailed measurements of the hollow beam phenomenon, including its distinct image pattern, spectrum signature, and its evolution with time. By capturing the post-instability bursting beam, the hollow beam is a unique model system for studying the transverse instabilities, in particular, the interplay of the wake field and the lattice nonlinearity. In addition, the hollow beam can be used as a powerful tool to study the linear and nonlinear particle dynamics in the storage ring.

 
RPAE022 Improved Long Radius of Curvature Measurement System for FEL Mirrors 1787
 
  • J. Li, C. Sun, Y.K. Wu
    DU/FEL, Durham, North Carolina
  
  Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370.

The 53.73 meter long Duke free electron laser (FEL) cavity consists of two concave mirrors with radius of curvature longer than 27 meters. A proper radius of curvature is designed to achieve an optimal and stable operation of the FEL. This requires accurate measurements of the cavity mirror's radius of curvature before its initial installation. Subsequent radius of curvature measurements are performed to ensure no significant deformation of the mirror occurs after a period of extensive use. A direct measurement based upon the geometric optics principles has been used at DFELL for years. Recently, we have significantly upgraded this measurement apparatus by utilizing a HeNe laser as the light source and a straight wire with a proper size as the object. In this paper we describe the details of the measurement setup and report the benefits of the recent upgrades. In addition, we report the improved data analysis technique and results of recent long radius of curvature measurements.

 
RPAE074 Recommissioning of Duke Storage Ring with a HOM-Damped RF Cavity and a New Straight Section Lattice for FELs 3934
 
  • Y.K. Wu, M.D. Busch, M. Emamian, J.F. Faircloth, J. Gustavsson, S.M. Hartman, C. Howell, M. Johnson, J. Li, S. Mikhailov, O. Oakeley, J. Patterson, M. Pentico, V. Popov, V. Rathbone, G. Swift, P.W. Wallace, P. Wang
    DU/FEL, Durham, North Carolina
  
  Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370 and by U.S. DoE grant DE-FG02-01ER41175.

The Duke FEL lab operates a unique UV/VUV storage ring FEL and an FEL driven, nearly monochromatic, highly polarized, high intensity Compton gamma-ray source. The Duke storage ring light source is undergoing several phases of upgrade in order to significantly improve light source capabilities and performance. The 2004 phase included an upgrade of the RF system with a high-order mode damped RF cavity and a new 34 meter long straight section lattice to host new FEL wigglers in the next phase. This upgrade was completed in August 2004 and storage ring and light source commissioning were completed in November 2004. This paper will provide an overview of this upgrade project and report our commissioning experience of the storage ring and light sources.

 
FPAE061 Status of the Booster Injector for the Duke FEL Storage Ring 3544
 
  • S. Mikhailov, M.D. Busch, M. Emamian, J.F. Faircloth, S.M. Hartman, J. Li, V. Popov, G. Swift, V. Vylet, P.W. Wallace, P. Wang, Y.K. Wu
    DU/FEL, Durham, North Carolina
  • O. Anchugov, N. Gavrilov, G.Y. Kurkin, Yu. Matveev, D. Shvedov, N. Vinokurov
    BINP SB RAS, Novosibirsk
  
  Funding: This work is supported by U.S. DOE grant # DE-FG02-01ER41175 and by AFOSR MFEL grant # F49620-001-0370.

This paper presents the current status of the booster synchrotron for the Duke FEL storage ring. The booster will provide full energy injection into the storage ring in a wide energy range from 0.27 to 1.2 GeV. When operating the Duke FEL storage ring as the High Intensity Gamma Source (HIGS) to produce gamma photons above 20 MeV with Compton scattering, continuous electron loss occurs. The top-off mode operation of the booster injector will enable the continuous operation of the HIGS facility by replenishing the lost electrons. The design requirement for a compact booster with the single bunch extraction capability remains a challenge for the machine development. Presently, the booster project is in the installation phase. The magnetic elements, vacuum chambers, injection and extraction kickers have been fabricated in the Budker Institute of Nuclear Physics, Russia. The diagnostic and control system is being developed in the FEL lab, Duke University. The commissioning of the booster synchrotron is planned for fall 2005.

 
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.