Author: Kim, S.H.
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.