• J.Y. Huang, Y.S. Bae, M.-H. Chun, Y.J. Han, S.-H. Jeong, H.-S. Kang, D.T. Kim, S.H. Kim, S.-C. Kim, I.S. Ko, H.J. Park, I.-S. Park, S.J. Park, Y.J. Park, S.Y. Rah, J.-H. Suh
  PAL, Pohang, Kyungbuk
• J.H. Hong, C. Kim
  POSTECH, Pohang, Kyungbuk

Funding: Work supported by Ministry of Science and Technology (MOST)

Beam diagnostics for PAL-XFEL physics calls for precision of femto-second in time structure and sub-micrometer in beam position measurement(BPM). Existing instruments can be used for standard diagnostics such as single bunch charge measurement, wire scanner or optical transition radiator for beam size measurement. Instead, major R&D efforts should be focused on the measurement of femto-second bunch structure using electro-optic crystal, coherent radiation and transverse deflecting cavity. Nanometer BPM technique being developed in collaboration with linear collider group will also be utilized for sub-micrometer BPM. Overall plan and the ongoing R&D activities will be presented.

• S.H. Kim
  ANL, Argonne, Illinois

Funding: Work supported by the U.S. Department of Energy under Contract No. W-31-109-ENG-38.

The peak fields on the beam axis and the maximum fields in the conductor of Nb3Sn superconducting undulators (SCUs) were calculated for an undulator period length of 16 mm. Using a simple scaling law for SCUs [1], the peak fields, as well as the conductor maximum fields and the current densities, were calculated for a period range of 8 to 32 mm. The critical current densities of commercially available Nb3Sn superconducting strands were used for the calculations. The achievable peak fields are limited mainly by the flux-jump instabilities at low fields. The possible or feasible peak field will also be compared with that achieved in prototype development of SCUs.

[1] S. H. Kim, Nucl. Instrum. Methods A, accepted for publication.