Author: Gu, Q.
Paper Title Page
MOPFI044 VHF Gun Research at SINAP 380
  • Q. Gu, L. Chen, W. Fang, G.Q. Lin
    SINAP, Shanghai, People's Republic of China
  The R&D work on the high power THz based on energy recovery linac (ERL) has been carried out in Shanghai Institute of Applied Physics (SINAP). One of the key components for the ERL is the high brightness electron source. The low frequency gun technology has been adopted, by comparing with the SRF gun and DC gun. In this paper, the design and cold test of a 250MHz gun will be presented.  
MOPFI045 Studying of Multipacting in Micro-pulse Electron Gun 383
  • L. Liao, W. Fang, Q. Gu, M. Zhang, M.H. Zhao
    SINAP, Shanghai, People's Republic of China
  Depending on the complexity of multipacting phenomenon, more works are focused on the occurrence of multipacting in the micro-pulse electron gun. In this paper, the multipacting resonance condition is determined in a reentrant cavity model of the gun. The resonance parameters work as the input for VORPAL simulations in order to achieve a steady state saturation in the cavity. The simulation results showed that the gun can give rise to electrons beam with high currents and short pulses.  
TUPEA035 Plasma Effect in the Longitudinal Space Charge Induced Microbunching Instability 1220
  • D. Huang, Q. Gu
    SINAP, Shanghai, People's Republic of China
  • K.Y. Ng
    Fermilab, Batavia, USA
  Funding: National Science Foundation of China (NSFC), grant No. 11275253, and US DOE, contract DE-FG02-92ER40747.
In many cases, the longitudinal space charge (LSC) is a dominant factor to bring in the microbunching instability in the LINAC of a Free-Electron-Laser (FEL) facility. The current model of LSC impedance* derived from the fundamental electromagnetic theor** is widely used to explain the physics of the LSC-induced microbunching instability***. However, in the case of highly bright electron beams, the plasma effect starts to play a role. In this paper, the basic model of the LSC impedance including the plasma effect is built up by solving the Vlasov and Poisson equations in 6 dimensional phase space, and the investigation is done to study the modification to the gain of the instability based on the model. The solutions indicate that the gain does not only depend on the spatial information of the beam, but also on the velocity (momentum) and time information. The comparison of the gains of the microbunching instability in the LINAC of Shanghai soft X-ray Free Electron Laser Facility (SXFEL) computed by various methods is also given and the discrepancy is illustrated.
* Marco Venturini, Phys. Rev. ST Accel. Beams 11, 034401 (2008)
** J. D. Jackson, Classical Electrodynamics (Wiley, 1999)
*** Z. Huang, et. al., Phys, Rev. ST Accel. Beams 7, 074401 (2004)
TUPEA042 Linac Design for Dalian Coherent Light Source 1226
  • M. Zhang, H.X. Deng, D. Gu, Q. Gu
    SINAP, Shanghai, People's Republic of China
  Dalian Coherent Light (DCL) Source is a FEL user facility in which HGHG scheme is adopted. Beam quality requirements for the linear accelerator (linac) are critical, including not only the beam brightness, but also the stability and the reliability. In this paper, optimization study is performed for the linac. Based on beam stability simulation in the longitudinal direction, the tolerant budget is formed for the short period jitter. For the transverse orbit error, beam based alignment (BBA) technique is implemented by beam dynamics simulations and the transverse jitter is also presented accordingly. Measurement method for the beam quality is also described in the paper.  
TUPEA043 Linac Design for Nuclear Data Measurement Facility 1229
  • M. Zhang, W. Fang, Q. Gu, X. Li
    SINAP, Shanghai, People's Republic of China
  Pulsed neutrons based on an electron linear accelerator (linac) are effective for measuring energy dependent cross-sections with high resolution by using the time-of-flight (TOF) technique. In this paper, we describe the 15-MeV linac design for the Nuclear Data project in Shanghai Institute of Applied Physics (SINAP). The linac has three operating modes and the maximum average power is 7.5kW. We describe the characteristics of the linac and the study of the beam dynamics is also presented.  
TUPWO030 Beam-based Alignment Simulation on Flash-I Undulator 1940
  • D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao
    SINAP, Shanghai, People's Republic of China
  • M. Vogt, N.J. Walker
    DESY, Hamburg, Germany
  In order to ensure the SASE process can take place in the whole FLASH-I undulator section, a straight beam trajectory is mandatory which can only be achieved through beam-based alignment (BBA) method based on electron energy variations. In this paper, a detailed result of simulation is presented which demonstrate that the alignment can be achieved within accuracy of a few 10 μm after several iterations. The influence of Quadrupole and BPM offsets, magnet-mover calibration errors, quadrupole gradient errors are also discussed.  
WEPFI038 R&D of New C-band Accelerating Structure for SXFEL Facility 2785
  • W. Fang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • L. Chen, X. Sheng
    BVERI, Beijing, People's Republic of China
  • D.C. Tong
    TUB, Beijing, People's Republic of China
  C-band high gradient accelerating structure is crucial technology for Shanghai Soft X-ray FEL facility. Based on the prototype, the optimized C-band accelerating structure is proposed, and the experimental model is ready for high power test. In this paper, optimization design and some experiment results are presented, also design, fabrication and cold test of experimental model are introduced.  
WEPFI039 New X-band Deflecting Cavity Design for Ultra-short Bunch Length Measure of FEL at SINAP 2788
  • J.H. Tan, W. Fang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  For the development of Free Electron Lasers (FEL) at SINAP, ultra-short bunch is the crucial requirement for excellent lasing performance. It’s big challenge for deflecting cavity to measure the length of ultra-short bunch, and higher deflecting gradient is required for higher measurement resolution. X-band travelling wave deflecting structure has features of higher deflecting voltage and compact structure, which is good performance at ultra-short bunch length measuring. In this paper, a new X-band deflecting structure was designed, operated at HEM11- 2π/3 mode. For suppressing the polarization of deflection plane of the HEM11 mode, two symmetrical caves are added on the cavity wall to separate two polarized modes. More details of design and simulation results are presented in this paper.  
WEPFI040 R&D of C-band Pulse Compression for Soft X-ray FEL at SINAP 2791
  • C.P. Wang, W. Fang, Q. Gu, W.C. Wang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  A compact Soft X-ray Free Electron Lasers facility is presently being constructed at SINAP, and 8 C-band accelerating structure unit are required for third-stage including 4 pulse compressors. The field mode of C-band SLED is TE0.1.15 with high quality factor Q, and the coupling coefficient is 8.5. Based on the design, the power pulse of klystron is compressed from 2.5μs to 0.5μs, and finally the power gain is about 3.1. In this paper, the details and simulation of 3-dB coupler, mode convertors and the resonant cavities are presented, meanwhile some cold test results of cavity are also analyzed at the end of this paper.