1) Feedback at the end of linac -- Glen White
2) Survivability of spoilers -- Lew Keller
3) CF&S progress -- Fred Asiri
4) Radiation study -- Alberto Fasso, Toshiya Sanami
5) Discussion of further cost reductions -- all


Glen presented considerations for feedback after the end of the linac, to straiten the train as it enters the BDS, on bunch-to-bunch bases. In comparison with previous results, the kicker strength seems doable. The required BPM resolution is 200nm which need to be studied. Overall modeling, including 5Hz upstream feedback, is needed to study this system further.

Lew presented results of survivability study for spoilers on beta and energy collimators. In both cases, the spoilers survive 2 bunches at 250GeV/beam and one bunch at 500GeV/beam. The MPS system would let through not more than two bunches. Additional improvements of MPS system would be needed at 500GeV/beam, to not let more than one bunch through. Thin (0.1rl) pre-radiators were discussed to ease the spoiler survival -- they would be placed ~10m before the spoilers, but they would however result in increased wakes.

 Fred presented snapshots of CFS BDS layouts, where the beam dump tunnels are now included.

Alberto Fasso and Toshiya Sanami (visiting from KEK, for one year) reported briefly about radiation studies they are doing. In case of 18MW lost at IP, assuming there is 3m of concrete around beamline, the level at the top of the 100m deep shaft is <1mrem/hr. Studies will also be done without such shielding at the IP, for comparison.

The group discussed various configurations which may reduce cost. One of them is shown in the attached slide, where the FF and E-coll is shortened by ~300m (the energy reach of the system will reduce) and, to keep the IP separation >28m, the diagnostic section is relocated downstream of BSY. The savings due to such change are however not very large.
    For the sake of studies, it was discussed to consider single IR systems which are not constrained by IP separation, and to study two configurations: first is optimized for 1TeV CM, and second one is up to 500 GeV CM only.

Andrei Seryi, 09/05/06