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Yan, L. X.

Paper Title Page
TUPMN053 Status of the Photocathode RF Gun at Tsinghua University 1043
  • Y.-C. Du, W.-H. Huang, Y. Lin, C.-X. Tang, D. Xiang, L. X. Yan
    TUB, Beijing
  The photocathode RF gun at Tsinghua University was built to develop electron source for the Thomson Scattering X-ray source. The main goal is to produce minimum transverse emittance beams with short bunch length at medium charge (~1nC). It includes a 1.6 cell S-band BNL/KEK/SHI type cavity, a solenoid for space charge compensation, a laser system to generate UV light, and different diagnostics tools. In this paper, it will include measurements of the dark current, the charge and quantum efficiency, momentum, transverse electron beam profiles at different locations and the transverse emittance.

This work was supported by the Chinese National Foundation of Natural Sciences under Contract no. 10645002.

TUPMN054 Design of a Source to Supply Ultra-fast Electron and X-Ray Pulses 1046
  • W.-H. Huang, H. Chen, Y.-C. Du, Hua, J. F. Hua, R. K. Li, Y. Lin, J. Shi, C.-X. Tang, D. Xiang, L. X. Yan, P.-CH. Yu
    TUB, Beijing
  In this paper we report the preliminary design and considerations on a multi-discipline ultra-fast source, which is capable of providing the user community with femtosecond electron bunch and light pulses with the wavelength ranging from IR to X-ray. The facility is based on photocathode RF gun driven by a Ti:Sapphire laser system. The low emittance subpicosecond electron bunch at the gun exit can be used in femtosecond electron diffraction setup to visualize the ultrafast structural dynamics. After acceleration and compression, the electron beam with the energy of 50 MeV is further used to provide high peak brightness X-ray by inverse Compton scattering with TW laser. We also consider the possibility and reliability of storing the electron beam in a compact storage ring and the laser pulse in a super-cavity. Operating in this scheme may increase the average flux of the X-ray photons by orders of magnitude.  
TUPMN055 First Principle Measurements of Thermal Emittance for Copper and Magnesium 1049
  • D. Xiang, Y.-C. Du, W.-H. Huang, R. K. Li, Y. Lin, C.-X. Tang, L. X. Yan
    TUB, Beijing
  • J. H. Park, S. J. Park
    PAL, Pohang, Kyungbuk
  Funding: This work was supported by the Chinese National Foundation of Natural Sciences under Contract no. 10645002.

There are growing interests in generation, preservation and applications of high brightness electron beam. With the rapid development in the techniques for emittance compensation and laser shaping, we are approaching the limit-the uncorrelated thermal emittance. In this paper, we report the measurements of thermal emittance for Cu and Mg. The measurement is conducted in a field-free region. The energy spectrum and angular distribution of the electrons are measured immediately after its emission and further used to reconstruct the initial phase space and the corresponding thermal emittance. We also show how cathode surface roughness* and laser incidence angle as well as its polarization state** affect the quantum efficiency and thermal emittance.

*X. Z. He, High energy physics and nuclear physics,28(2004)1007.**Dao Xiang,et al, NIM A,562(2006)48.

  • L. X. Yan, J. P. Cheng, Y.-C. Du, W.-H. Huang, Y. Lin, C.-X. Tang
    TUB, Beijing
  Funding: The work was supported by the Program for New Century Excellent Talents in University and the National Natural Science Foundation of China (No.10645002)

The ultrashort ultraviolet (UV) laser system and the optical transport line for driving the photocathode RF gun at Accelerator Laboratory of Tsinghua University are introduced in the article. Temporal profile of the UV pulse was measured by non-colinear difference frequency generation (DFG) between the UV pulse itself and the jitter-free residual IR laser pulse after third harmonic generation (THG) process. Experiments to measure the dependence of quantum efficiency (QE) on laser polarization state are also performed. Results show that in our case the ratio of QE between p- and s- polarization is more than 2.6.