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CLIC Beam Physics Meeting
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Europe/Zurich
6/2-004 (CERN)
Participants: A. Aksoy, A.K. Ciftci, B. Dalena, D. Egger, K. Elsener, L. Gatignon, E. Gschwendtner, E. Marin, Ö. Mete, L. Rinolfi, D. Schulte, J. Snuverink, F. Stulle, R. Tomas, G. Vanbavinckhove, A. Vivoli, T. Wilson, A.N. Yuksel, G. Zamudio, K. Zengin
D. Schulte presented some questions raised at the CLIC meeting on physics and detector issues on Friday 07/08/09. During that meeting it became obvious that CLIC accelerator and physics communities do make different assumptions on capabilities of CLIC. One prominent request by physics is to run at lower energy, may be even at Z0 energies, whereas from the accelerator side only changes up to a few percent are foreseen. D.S. showed that the luminosity has a quadratic dependence on the main linac gradient. Hence, if half energy would be requested only a quarter of the luminosity would be delivered.
L. Rinolfi asked if it would be possible to compensate by increasing the bunch train length. D.S. said this would be limited by drive beam capabilities.
T. Wilson asked how ILC foresees to lower energy. D.S. answered that the main problem for ILC is the positron production which relies on an electron beam with a certain energy. In the past there had been schemes for this but since the layout has changed they are not valid anymore. Newer considerations do not seem to exist.
T.W. said that in some discussions particle physicists would claim the large energy spread of the CLIC beam would render it useless and thus ILC would be preferable. D.S. responded that the energy spread would broaden the luminosity peak. But this should not have too large influence as long as peak would have similar height. In any case lowering the energy spread would only be feasible when lowering luminosity.
R. Tomas asked which hardware changes would have to be made to the BDS to accomplish low energy runs. D.S. answered that at least the final double would have to be exchanged. The collimators might have to be exchanged also or they have to be tunable.
T.W. wondered if it would be possible to optimize CLIC for 1.5TeV cm energy and then push it to high energies. D.S. informed that then the structures and the hole layout would have to be re-optimized.
D.S. asked to evaluate the consequences in all CLIC sub-systems in case of low energy runs. Higher bunch charge, higher repetition rate and longer bunch trains should be considered. Results will be discussed in three weeks on Wednesday 16/09/09.
T.W. asked if the damping ring layout has changed. If yes, he would like to have a new lattice. A. Vivoli agreed to send it.
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