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CLIC Beam Physics Meeting
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Europe/Zurich
6/2-004 (CERN)
Description
Drive Beam Issues
Participants: E. Adli, C. Biscari (via WebEX), B. Dalena, B. Jeanneret, J. Pfingstner, L. Rinolfi, D. Schulte, F. Stulle, T. Touze, A. Vivoli
B. Jeanneret presented the current status of the drive beam combiner rings. Lattices are existing, which are isochronous to second order. Unfortunately, they show strong transverse chromatic effects. A large filamentation is to be expected due to a large detuning. To ease the design he asked if the baseline of 2% energy transport is really required, since also in other parts of the drive beam line the assumed energy spread is lower. He emphasized that similar chromatic problems should occur at CTF3. This was discussed earlier with R. Corsini and will be studied experimentally. It might explain some of the unexpected measurement results. During his study, B.J. discovered an error in MAD8 and MADX which leads to a wrong calculation of second order chromaticity. Since this error is not easy to solve, B.J. elaborated an input file for matching to second order utilizing the PTC module of MADX, which is correct. The further steps for the combiner ring design will be discussed with C. Biscari. D. Schulte asked, if it would help to double the length of the combiner rings. This would be possible if really required. In this case two pulse would have to be accumulated at the same time.
E. Adli reported on recent beam dynamics studies for the decelerator. The major problem is the huge energy spread which leads to a huge spread in betatron frequencies and a huge beam size. Quadrupole misalignment and wake fields will both lead to strong orbit errors. Dispersion Free Steering mitigates this, but shows a strong dependence on BPM resolution. The number of BPMs might be reduced by 50%. The influence of alternative PETS designs was studied, including the currently discussed option for recirculation. Following the presentation it was discussed how the required quadrupole strengths could be realized in a cost efficient way.
D. Schulte reminded everybody to send magnet specification to F. Stulle. A draft magnets list will be presented next week.
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