• J.Y. Huang, Y.S. Bae, M.-H. Chun, Y.J. Han, S.-H. Jeong, H.-S. Kang, D.T. Kim, S.H. Kim, S.-C. Kim, I.S. Ko, H.J. Park, I.-S. Park, S.J. Park, Y.J. Park, S.Y. Rah, J.-H. Suh
  PAL, Pohang, Kyungbuk
• J.H. Hong, C. Kim
  POSTECH, Pohang, Kyungbuk

Funding: Work supported by Ministry of Science and Technology (MOST)

Beam diagnostics for PAL-XFEL physics calls for precision of femto-second in time structure and sub-micrometer in beam position measurement(BPM). Existing instruments can be used for standard diagnostics such as single bunch charge measurement, wire scanner or optical transition radiator for beam size measurement. Instead, major R&D efforts should be focused on the measurement of femto-second bunch structure using electro-optic crystal, coherent radiation and transverse deflecting cavity. Nanometer BPM technique being developed in collaboration with linear collider group will also be utilized for sub-micrometer BPM. Overall plan and the ongoing R&D activities will be presented.

• E.-S. Kim, Y.J. Han, J.Y. Huang, S.J. Park
  PAL, Pohang, Kyungbuk

Longitudinal space charge wake is an important source that can generate microbunching instability at accelerator systems for X-ray free-electron laser. We present investigation to minimize gain of energy modulation due to the longitudinal space charge wakes that are caused at RF photocathode gun, two bunch compressors and linac at the PAL-XFEL, which include optimization of parameters for two bunch compressors and consideration of a laser heater. These studies are performd by using integral equation and numerical simulation methods. Design studies of a system for the laser heater are presented. We also show simulation results on effects of interaction between electron beam and laser.

• S.J. Park, J.Y. Huang, I.S. Ko, J.-S. Oh, Y.W. Parc, P.C.D. Park, J.H. Park
  PAL, Pohang, Kyungbuk
• C. Kim
  POSTECH, Pohang, Kyungbuk
• X.J. Wang
  BNL, Upton, Long Island, New York
• D. Xiang
  TUB, Beijing

Funding: Work supported by the MOST and the POSCO.

The PAL XFEL, an X-Ray Free Electron Laser (XFEL) project based on the Self-Amplified Spontaneous Emission (SASE), is under progress at the Pohang Accelerator Laboratory (PAL). Successful completion of the project is expected to impose stringent requirements on the beam qualities such as the normalized emittance (< 1.2 mm-mrad) and the un-correlated energy spread (~10(-5)). This requires careful and systematic planning for ensuring the generation and the preservation of high-brightness beams in the whole machine. The PPI (Pohang Photo-Injector) is to achieve these requirements with high reliability and stability. In this article, we discuss various physics and engineering issues involved in the design and construction of the PPI. We also report on the R&D status of photo-cathode RF gun at the PAL.