• J.Y. Ryu, E.-S. Kim, H.D. Kim, H.K. Park
  KNU, Deagu
• J.G. Hwang
  Kyungpook National University, Daegu
• C. Kim
  PAL, Pohang, Kyungbuk

The syn­chrotron-ra­di­a­tion in­ter­fer­om­e­ter was em­ployed for the beam size mea­sure­ment of elec­tron beam cir­cu­lat­ing in the stor­age ring at 2.5 GeV Po­hang Light Source. We mea­sured the beam sizes in both ver­ti­cal and hor­i­zon­tal di­rec­tions as func­tion of stored beam cur­rent. In this pre­sen­ta­tion, we will dis­cuss the in­ter­fer­om­e­ter sys­tem, anal­y­sis method for the mea­sure­ment and the mea­sured re­sults. We also com­pared the mea­sured beam sizes with pre­dict­ed val­ues from the lat­tice pa­ram­e­ters in the ring.

• C.M. Yim, S. Noh
  POSTECH, Pohang, Kyungbuk
• H.-S. Kang, C. Kim, I.S. Ko
  PAL, Pohang, Kyungbuk

At Po­hang Ac­cel­er­a­tor Lab­o­ra­to­ry, a fem­to-sec­ond THz fa­cil­i­ty was con­struct­ed for the ex­per­i­ments using fem­to-sec­ond THz ra­di­a­tion. The fs-THz ra­di­a­tion is gen­er­at­ed from 60-MeV elec­tron linac which con­sists of a pho­to­cath­ode RF gun, two ac­cel­er­at­ing columns, and two mag­net­ic-chi­cane bunch com­pres­sors. The co­her­ent tran­si­tion ra­di­a­tion (CTR) is used for THz ra­di­a­tion gen­er­a­tion. To gen­er­ate high in­ten­si­ty THz ra­di­a­tion, the elec­tron bunch length should be small­er than 200 fs. We re­port THz image ob­tained using IR-CCD　cam­era and mea­sured beam pa­ram­e­ters in­clud­ing bunch length, en­er­gy spread, charge, emit­tance, and trans­verse beam size.

• 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.

• I. Hwang, C. Kim, K.R. Kim, M. Kim, S.H. Nam, S.J. Park, S. Shin
  PAL, Pohang, Kyungbuk
• J. Hou, L.G. Liu
  SINAP, Shanghai

The mea­sure­ment and the con­trol of the cou­pling is es­sen­tial to max­i­mize syn­chrotron per­for­mance. Small cou­pling is re­quired for small ver­ti­cal size and high bright­ness. The Po­hang Light Source has a 2.5 GeV stor­age ring and its cou­pling con­stant is mea­sured as about 1%. In ad­di­tion to er­rors at quadrupole or sex­tupole, the con­di­tion vary­ing of the in­ser­tion de­vice af­fects the cou­pling. The cou­pling for var­i­ous con­di­tion is mea­sured by the res­o­nance and the re­sponse ma­trix and com­pared with the beam size and the life­time. The cor­rec­tion and the con­trol of the cou­pling is pre­sent­ed.

• Y.D. Joo, T. Ha, C. Kim, C.D. Park, S.J. Park
  PAL, Pohang, Kyungbuk

A su­per­con­duct­ing RF cav­i­ty is used in the stor­age ring of the Po­hang Light Source (PLS) up­grade pro­ject (PLS-II) at Po­hang Ac­cel­er­a­tor Lab­o­ra­to­ry (PAL) for in­creas­ing the elec­tron beam cur­rent and en­er­gy from 2.5GeV/200mA to 3.0GeV/400mA. In order to meet the re­quire­ment of lower beam emit­tance and high­er pho­ton en­er­gies, as well as more straight sec­tions for in­ser­tion de­vices, the vac­u­um cham­bers in the stor­age ring need to be re­con­struct­ed. To con­trol the spu­ri­ous har­mon­ic res­o­nances' ef­fect to beam po­si­tion mon­i­tors (BPMs) in the PLS and PLS-II stor­age ring vac­u­um cham­ber, the TE mode dis­tri­bu­tion in vac­u­um cham­bers has been an­a­lyzed by both nu­mer­i­cal sim­u­la­tion and ex­per­i­ment. Based on this anal­y­sis, the prop­er method to con­trol the strength of TE mode at the po­si­tion of BPMs is sug­gest­ed.