• 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.