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[Ext-GDE-61] CCB Response BDS (Beam Crossing Angles) Change Config Request of July 29, 2006



Dear Colleagues,

I am announcing that the CCB response, with regards to the latest
Change Request for the Beam Delivery section, is now posted at -

   http://www.linearcollider.org/wiki/lib/exe/fetch.php?cache=cache&media=bcd:ccb-com-bds20060908.pdf

The change request was submitted by A.Seryi on July 29, 2006.
It relates to reconfiguration of the two-IR layout to be based
on beam crossing angles of 14mrad/14mrad rather than the previous
20mrad/2mrad, and to place two detectors within a same experimental
hall having the same Z location.

The requester suggested Class 2 for this request, to which
CCB concurred after evaluation of the cost impact.
CCB gratefully acknowledges the detailed assessment reports offered
by colleagues from the WWS/MDI, Magnet Technical System Group, as well
as the GDE Cost Engineers besides the colleagues from the BDS Area
System Group.

The summary CCB response is as follows -

1. CCB agrees that the cost change (in this case, reduction) expected
   from this change request is substantial, such that it qualifies as
   Class-2. Consequently, rather than making a final configuration change
   decision, based on an assessment on the technical and cost merits, CCB
   makes a recommendation to EC.
2. CCB recommends EC to adopt this change request as is, for reasons
   detailed in the Discussion section (see URI above).
3. CCB will encourage the relevant parties, and will work with them, to
   update the "Parameters and Layout" section of BCD in accordance with
   the new beam crossing angle (14mrad/14mrad) at the interaction point.

Additional communication and reference materials are available for
viewing, under CCR #14, at

   http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_history

When GDE EC makes the final decision and approves this change request,
CCB will update the BCD section under

   http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_home

CCB notes the rather long time that it took to bring out this
recommendation. Part of the time was spent on nailing down the protocols
associated with the Class-2 review in conjunction with the cost information
handling. CCB greatly acknowledges the cooperation offered by the GDE
Cost Engineers, expresses its thanks to BDS Area Group leaders for their
patience, and hopes that other, similar change requests be handled more
expeditiously in the future.

With best regards,

- Nobu Toge (KEK, Accelerator Lab)
  email: toge@xxxxxxxxxxxx
  voice: +81-29-864-5224
  fax:   +81-29-864-3182