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The ILC positron beam generated from a thin Ti target has a wide energy spread and large transverse divergence. With the collection optics immediately downstream of the target and pre-acceleration to 125 MeV, the collected positron beam still has a long tail of positrons with low energies and large transverse divergence, which will be lost in the rest of the ILC positron source beamline. A collimation system is proposed and optimized for the case of a shielded target with quarter-wave transformation collection optics so that the power loss in the magnets and RF structures is effectively controlled within the acceptable level and in the damping ring (DR) within 640 W, assuming 3× 1010 of the captured positrons per bunch in the DR. In this case, the capture efficiency and DR injection efficiency are 13% and 99.8%, respectively. The lower capture efficiency is expected to result in higher injection efficiency and therefore, a lower power loss in the DR. The capture efficiency for the cases of a shielded target with flux concentrator and 5-T immersed target with flux concentrator is 20% and 30%, respectively, with the collimation system.
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- J. A. Clarke, O. B. Malyshev, D. J. Scott
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- I. R. Bailey, J. B. Dainton, K. M. Hock, L. J. Jenner, L. I. Malysheva, L. Zang
Liverpool University, Science Faculty, Liverpool
- E. Baynham, T. W. Bradshaw, A. J. Brummitt, F. S. Carr, A. J. Lintern, J. Rochford
STFC/RAL, Chilton, Didcot, Oxon
- V. Bharadwaj, J. Sheppard
SLAC, Menlo Park, California
- A. Bungau
UMAN, Manchester
- N. A. Collomb
STFC/DL, Daresbury, Warrington, Cheshire
- R. Dollan
Humboldt Universität zu Berlin, Berlin
- W. Gai, Y. Ivanyushenkov, W. Liu
ANL, Argonne, Illinois
- J. Gronberg, W. T. Piggott
LLNL, Livermore, California
- A. F. Hartin
OXFORDphysics, Oxford, Oxon
- S. Hesselbach, G. A. Moortgat-Pick
Durham University, Durham
- K. Laihem, S. Riemann, A. Schaelicke, A. Ushakov
DESY Zeuthen, Zeuthen
- T. Lohse
Humboldt University Berlin, Institut für Physik, Berlin
- A. A. Mikhailichenko
Cornell University, Department of Physics, Ithaca, New York
- N. C. Ryder
University of Bristol, Bristol
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