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Change Request Action - Central Damping Rings



Colleagues:

I would like to announce that the GDE Executive Committee has officially approved the Change Request (CCR#18) for Parameter / Layout section of the GDE ILC Baseline Configuration Document as recommended by our Change Control Board. This was a Class-2 change that requires EC approval. This change redefines the ILC layout such that the electron and positron damping rings will be contained in a single, common tunnel which is situated centrally around the interaction regions. The new layout will now officially become our baseline.

The main motivation for this change is the substantial cost reduction by eliminating the entire civil construction costs for one 6 km damping ring tunnel and consolidating the conventional facilities for the damping rings. There are some compensating new costs in beam transport, those are small compared to the civil construction savings.

Many details resulting from this change are still to be worked out, but it was the judgement of the CCB and the EC that those will not change the conclusions to make this change and therefore we feel we can make this change and defer some of the detailed optimization until after the RDR is complete. Nevertheless, it is important to bring the BCD document up to date as soon as possible.

I would especially like to thank Ewan Paterson for so effectively completing this study and bringing a well-worked CCR to our CCB and I also note and appreciate the concerted and rapid work of the CCB in bringing this action to completion.

Barry
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