Author: Namkung, W.
Paper Title Page
MOPC035 Design and Machine Features of 2.2-m C-band Accelerating Structure 148
 
  • C.H. Yi, M.-H. Cho, S.H. Kim, H. Lee
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Namkung
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: This work is partly supported by the MEST, Korea and POSTECH BK21 Program. And this work was supported by the Korea Student Aid Foundation (KOSAF) grant funded by the Korea government.
A com­pact linac sys­tem is de­signed using a longer ac­cel­er­at­ing col­umn in a C-band linac. It re­duces the total num­ber of RF units for the given linac beam en­er­gy and re­sults in the cost-ef­fec­tive use of RF pow­ers. For the 10 GeV PAL-XFEL pro­ject, a C-band ac­cel­er­at­ing col­umn of 2.2-m long is in­ves­ti­gat­ed, which is 22% longer than 1.8-m for the SACLA at SPring-8. The de­tailed RF and ther­mal char­ac­ter­is­tics are pre­sent­ed by an an­a­lyt­ic model.
 
 
MOPS035 Energy Spreads by Transient Beam Loading Effect in Pulsed RF Linac 679
 
  • S.H. Kim, M.-H. Cho, G. Ha, H.R. Yang
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Namkung, S.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
  • J.-S. Oh
    NFRI, Daejon, Republic of Korea
 
  Funding: Work partly supported by KAPRA and POSTECH Physics BK21 Program
RF linacs for high power beams are op­er­at­ed in the fully beam-load­ed con­di­tion for the power ef­fi­cien­cy. In this con­di­tion, tem­po­ral en­er­gy spreads are in­duced by the tran­sient beam load­ing ef­fect. Ir­ra­di­a­tion sources re­quire the beam en­er­gy of less than 10 MeV to pre­vent un­de­sir­able neu­tron pro­duc­tion. In order to max­i­mize the beam power and main­tain the beam en­er­gy in a safe value, we need to sup­press the tem­po­ral en­er­gy spreads. In an L-band trav­el­ing-wave linac for ir­ra­di­a­tion sources, the high en­er­gy elec­trons are sup­pressed by the beam cur­rent mod­u­la­tion with the RF power mod­u­la­tion. As a re­sult, the av­er­age beam en­er­gy and the cor­re­spond­ing beam power are im­proved by near­ly 60% com­pared to the case with­out any mod­u­la­tions.
 
 
TUPS014 Vacuum Performance Simulation of C-band Accelerating Structures 1548
 
  • H. Lee, M.-H. Cho, S.H. Kim, C.H. Yi
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Namkung, C.D. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: This work is partly supported by the MEST and POSTECH Physics BK21 program.
A C-band ac­cel­er­at­ing struc­ture has a high­er ac­cel­er­at­ing gra­di­ent than that of the S-band struc­ture. It pro­vides a good ad­van­tage of a short­er ma­chine length. In order to ef­fec­tive­ly use RF power and for cost re­duc­tion, the ac­cel­er­at­ing struc­ture should be as long as pos­si­ble. We pro­pose a 2.2-m long struc­ture com­pared to 1.8-m at SACLA (SPring-8 Angstrom Com­pact free elec­tron LAser). How­ev­er, a longer ac­cel­er­at­ing struc­ture has worse vac­u­um per­for­mance than a short­er ac­cel­er­at­ing struc­ture. Thus, the vac­u­um con­duc­tance of 2.2-m long struc­ture has to be checked. We cal­cu­late vac­u­um per­for­mance of the ac­cel­er­at­ing struc­ture by 1-D an­a­lyt­i­cal method and 3-D fi­nite el­e­ment method (FEM). It is shown that the vac­u­um per­for­mance for the 2.2-m long ac­cel­er­at­ing struc­ture is safe enough for the XFEL LINAC.
 
 
WEPC018 Self-focusing Effects in Compact C-band Standing-wave Accelerating Structure for X-ray Imaging Applications 2046
 
  • H.R. Yang, M.-H. Cho, S.H. Kim, W. Namkung, S.J. Park
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • J.-S. Oh
    NFRI, Daejon, Republic of Korea
 
  In elec­tron RF linacs for in­dus­tri­al X-ray imag­ing ap­pli­ca­tions, com­pact struc­tures are pre­ferred for mo­bil­i­ty. The elec­tron beam spot size of 1 – 2 mm is re­quired for the spa­tial res­o­lu­tion of im­ages at the X-ray con­ver­sion tar­get. Ap­ply­ing self-fo­cus­ing ef­fects to the ac­cel­er­at­ing struc­ture, ex­ter­nal mag­nets can be re­moved and then the ac­cel­er­a­tor sys­tem be­comes more com­pact. We de­sign a C-band elec­tron linac, which is ca­pa­ble of pro­duc­ing 6-MeV, 80-mA pulsed elec­tron beams with an RF power of 1.5 MW. It uses a bi-pe­ri­od­ic and on-ax­is-cou­pled ac­cel­er­at­ing struc­ture with a built-in bunch­ing sec­tion. It uses the π/2-mode stand­ing-waves. The first bunch­ing cell has an asym­met­ric ge­om­e­try which max­i­mizes the RF phase fo­cus­ing. On the other hand, the nor­mal cells are de­signed for the elec­tro­stat­ic fo­cus­ing to be max­i­mized. In this paper, we pre­sent de­sign de­tails of the ac­cel­er­at­ing cells and the beam dy­nam­ics sim­u­la­tion by the PARMELA code.