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Chen, J.

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TUPMS041 The Wisconsin VUV/Soft X-ray Free Electron Laser Project 1278
 
  • J. Bisognano, R. A. Bosch, M. A. Green, H. Hoechst, K. Jacobs, K. J. Kleman, R. A. Legg, R. Reininger, R. Wehlitz
    UW-Madison/SRC, Madison, Wisconsin
  • J. Chen, W. Graves, F. X. Kaertner, J. Kim, D. E. Moncton
    MIT, Cambridge, Massachusetts
 
  Funding: Work supported by the University of Wisconsin - Madison. SRC is supported by the U. S. National Science Foundation under Award No. DMR-0537588.

The University of Wisconsin-Madison and its partners are developing a design for an FEL operating in the UV to soft x-ray range that will be proposed as a new multidisciplinary user facility. Key features of this facility include seeded, fully coherent output with tunable photon energy and polarization over the range 5 eV to 1240 eV, and simultaneous, independent operation of multiple beamlines. The different beamlines will support a wide range of science from femto-chemistry requiring ultrashort pulses with kHz repetition rates to photoemission and spectroscopy requiring high average flux and narrow bandwidth at MHz rates. The facility will take advantage of the flexibility, stability, and high average pulse rates available from a CW superconducting linac driven by a photoinjector. This unique facility is expected to enable new science through ultra-high resolution in the time and frequency domains, as well as coherent imaging and nano-fabrication. This project is being developed through collaboration between the UW Synchrotron Radiation Center and MIT. We present an overview of the facility, including the motivating science, and its laser, accelerator, and experimental systems.

 
TUPMS042 A Superconducting Linac Driver for the Wisconsin Free Electron Laser 1281
 
  • J. Bisognano, R. A. Bosch, M. A. Green, K. Jacobs, K. J. Kleman, R. A. Legg
    UW-Madison/SRC, Madison, Wisconsin
  • J. Chen, W. Graves, F. X. Kaertner, J. Kim
    MIT, Cambridge, Massachusetts
 
  Funding: Work supported by the University of Wisconsin - Madison. SRC is supported by the U. S. National Science Foundation under Award No. DMR-0537588.

We present an initial design of the driver for the Wisconsin VUV/Soft Xray FEL facility, which will provide high intensity coherent photons from 5 eV to 1.2 keV. It uses a 2.5 GeV, L-band CW superconducting linac with a 1.7 GeV tap-off to feed the lower energy FELs. In order to support multiple high rep-rate FELs, the average design current is 1 mA. Sub-nanocoulomb bunches with normalized transverse emittances of order 1 micron are generated in a photoinjector for beamlines operating at repetition rates from kHz to MHz. Multi-stage bunch compression provides 1 kA peak current to the FELs, with low energy spread and a suitable current profile. Compressed bunch lengths of several hundred femtoseconds will allow generation of photon pulses in the range 10 to 100 fs using cascaded FELs. Consideration has been given to removing the residual energy chirp from the beam, and minimizing the effects of space charge, coherent synchrotron radiation, and microbunching instabilities. A beam switchyard using RF separators and fast kickers delivers the desired electron bunches to each of the FELs. Details of the design will be presented, including those areas requiring the most development work.

 
MOPAN094 Operation Experiences of the Bunch-by-Bunch Feedback System for TLS 383
 
  • K. T. Hsu, J. Chen, P. C. Chiu, S. Y. Hsu, K. H. Hu, C. H. Kuo, D. Lee
    NSRRC, Hsinchu
 
  Severe multi-bunch instabilities are bothered the operation of Taiwan Light Source (TLS) during the operation during 2004 just after SRF system upgrade. FPGA-based bunch-by-bunch feedback system was commissioning during late 2005 and early 2006. Multi-bunch instability in both transverse plans and longitudinal are well control. Delivery up to 400 mA stored beam was demonstrated. Transverse feedback system make low chromaticity operation is possible; this is very helpful to improve injection efficiency which are essential for routine top-up operation. Operation experiences of the bunch-by-bunch feedback system will be summary in this report.  
MOPAN103 New Control System for the 50 MeV Linear Accelerator of TLS 404
 
  • C. Y. Wu, J. Chen, K. T. Hsu, S. Y. Hsu, J.-Y. Hwang, D. Lee, K.-K. Lin, C.-J. Wang
    NSRRC, Hsinchu
 
  The preinjector of the Taiwan Light Source(TLS) is consist of a 140 kV themionic gun and a 50 MeV traveling wave type linear accelerator system. In order to improve performance, to decouple the vacuum interlock logic from the linac control system, and to provide a better control functionality for top-up operation and to avoid obsolescence, linac control system have been renew. One VME crate system is dedicated for linac control, new hardware equips with high resolution of analog interface to provide better control. Vacuum interlock logic will be done be a dedicated programmable logic controller(PLC). The remained linac devices have sequential control needed will be done by another PLC, such as door access interlock, klystron warm up, gun warm up, trig interlock, gun high voltage interlock, klystron modulator high voltage interlock, water flow interlock. Both interlock and sequence control PLC will control by the VME crate. All the other functions without interlock or sequence requirement will control by the VME crate directly. New control system expects to provide better control functionality, better performance, easy for maintenance, and useful easy to add new hardware equipments.  
TUPMN074 Improvements to the Injection Efficiency at the Taiwan Light Source 1091
 
  • Y.-C. Liu, H.-P. Chang, J. Chen, P. J. Chou, K. T. Hsu, K. H. Hu, C. H. Kuo, C.-C. Kuo, K.-K. Lin, G.-H. Luo, M.-H. Wang
    NSRRC, Hsinchu
 
  Taiwan light source started the 200 mA top-up operation in October 2005, and the stored beam current was subsequently ramped up to 300 mA top-up operation. In the early phase of top-up operation, the injection efficiency had large variation at different machine condition. We have developed the procedures to maintain the injection efficiency. These optimization procedures will be activated whenever the injection efficiency degrades during the top-up operation of TLS.  
FROAC04 Sub-10 Femtosecond Stabilization of a Fiber Link Using a Balanced Optical Cross Correlator 3804
 
  • F. Loehl, H. Schlarb
    DESY, Hamburg
  • J. Chen, F. X. Kaertner, J. Kim, F. Wong
    MIT, Cambridge, Massachusetts
  • J. M. Mueller
    TUHH, Hamburg
 
  Synchronization of various components with fs stability is needed for the operation of free-electron-lasers such as FLASH or the European XFEL. One possibility to realize a high precision synchronization is to use a mode-locked Er-doped fiber laser as a master clock and to distribute ultra short laser pulses inside the machine using actively stabilized fiber links. In this paper we demonstrate the stabilization of a 300 m long fiber link with a self-aligned balanced cross-correlator using a single type II phase-matched PPKTP crystal. This approach allowed us to reduce the timing jitter added by the link to below 10 fs.  
slides icon Slides  
FRPMN082 Diagnostic and Timing Supports for Top-Up Injection Operation for the TLS 4252
 
  • J. Chen, P. C. Chiu, K. T. Hsu, S. Y. Hsu, K. H. Hu, C. H. Kuo, D. Lee, C.-J. Wang, C. Y. Wu
    NSRRC, Hsinchu
 
  Routine top-up operation of Taiwan Light Source (TLS) was started from October 2005 after high efficiency multi-bunch instabilities suppression system put into service. To support the top-up operation, various diagnostics and timing supports are needed. These include diagnostics for injection efficiency, filling pattern of the storage ring, tune, instability, loss pattern measurement. Timing control of the injection process are also needed. Design consideration and details of these efforts will be summary in this report. Further possible improvement will be also discussed.  
FRPMN084 Beam Trip Event Diagnostic System for the TLS 4264
 
  • K. H. Hu, J. Chen, K. T. Hsu, C. H. Kuo, C. Y. Wu
    NSRRC, Hsinchu
 
  The beam trip event diagnostic system includes several eight channels high-speed digitizer for data acquisition, PC base computer and optical fibre network applies to capture data. The PC are also to serve signal processing, beam trip event analysis and archive. This system can integrate beam trip, interlock signal of SRF, waveform of the injection kicker, quench and interlock signal of the superconducting insertion device, and instability of the stored beam. This diagnostic system can be routine monitor signal and record beam trip event. Design consideration and details of the implementation will be summarized in this report.  
FRPMN085 Application of the IEEE-1394 and the GigE Vision Digital Cameras for Diagnostics in Taiwan Light Source 4270
 
  • C. H. Kuo, J. Chen, K. T. Hsu, S. Y. Hsu, K. H. Hu, D. Lee, C.-J. Wang, C. Y. Wu
    NSRRC, Hsinchu
 
  Digital camera has been adopted for the booster, storage ring and transport-line diagnostic recently at the Taiwan Light Source. The system provides low image distortion and lossless image transmission over long distances. The system is integrated with commercial software in the control system. The fully remote control supports various operations and application that is useful. These applications include of screen monitor equip in the booster and storage ring, wider dynamic range sensor and highly flexibility control for the emittance measurement in the transport line, booster and linac. System configuration and present status will be summarized in this report.  
FRPMN086 Beam Position Monitoring System Upgrade for the TLS 4276
 
  • C. H. Kuo, J. Chen, P. C. Chiu, K. T. Hsu, K. H. Hu
    NSRRC, Hsinchu
 
  Taiwan light source (TLS) equips with 59 beam position monitors (BPM). Existing Bergos's type multiplexing BPM electronics are working well during last decade. To improve the functionality of the BPM system, new type of BPM electronics (Liberal Electron) will be replace some existing multiplexing BPM electronics. Seamless integration of two kinds of electronics is via reflective memory. The high precision closed orbits were measured by multiplexing BPM via multi-channel PMC form factor 16-bits ADC modules and gigabit Ethernet fast access channel of Libera Electron. Turn-by-turn beam position measurement is also supported by new BPM electronics. Tune measurement is also possible by spectra analysis of the turn-by-turn beam position data. The preliminary version of the orbit data was sampled every millisecond. Fast orbit data were shared by reflective memory network to support fast orbit feedback application. Averaged data were updated to control database at a rate of 10 Hz. The system structure, software environment and preliminary beam test of the BPM system are summarized in this report.