• J.H. Hong, M.S. Chae, I.S. Ko, S.-I. Moon, Y.W. Parc
  POSTECH, Pohang, Kyungbuk
• C. Kim, S.J. Park
  PAL, Pohang, Kyungbuk

A Brookhaven National Laboratory (BNL) type S-band photocathode RF gun is used at Pohang Accelerator Laboratory (PAL) to produce femtosecond tera hertz (fs-THz) radiation. In order to upgrade the fs-THz Facility at PAL, we need to develop the performance of the RF gun. The requirements for new RF gun are following: 1 nC beam charge, 60 Hz repetition frequency and 1 mm mrad normalized rms transverse emittance. A dual feed photocathode RF gun is designed satisfy these requirements. Two additional pumping ports are used to remove the field asymmetry. A large radius and short length of the iris increases the mode separation. The coupling scheme is changed to make the fabrication simpler. The RF gun structure had been modeled using 3D field solver to provide the desired RF parameters and to obtain the field profile. In this paper the new RF gun design and the cold test results will be presented.

• Y.W. Parc
  PAL, Pohang, Kyungbuk
• M.S. Chae, J.H. Hong, I.S. Ko
  POSTECH, Pohang, Kyungbuk

Due the field asymmetry in RF gun due the holes in full cell cavity, the emittance of electron beam can be increased. To generate the low emittance electron beam for XFEL, the elimination of the each field components is very important. The RF field can be decomposed as dipole and quadrupole components. The effect on the emittance increase of each component is studied in this presentation by numerical method. The 3D field map is constructed by MATLAB code as input of PARMELA code with each component distribution of the RF field. In this paper the emittance increase of electron beam by the each component of the RF field will be presented.