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[Ext-GDE-102] CCB Response to BDS Change Request - Nov.29, 2006 (CCR#23)



Dear Colleagues,

I am announcing that the CCB response, with regards to the ILC Config
Change Request for the Beam Delivery Systems (BDS) section of 
Nov. 29, 2006 (CCR#23, http://lcdev.kek.jp/ML/PubCCB/msg00130.html,
http://lcdev.kek.jp/ML/PubCCB/msg00133.html) is now posted as

   http://www.linearcollider.org/wiki/lib/exe/fetch.php?cache=cache&media=bcd:ccb-com-bds20061223.pdf

The change request (CCR#23) was submitted by A.Seryi, representing 
the BDS AG leaders of GDE. CCR#23 was initially classified as 
Class-2, and later was confirmed as such at the CCB Hearing that was
held on Dec.15, 2006. The minutes of this CCB hearing is available at

   http://www.linearcollider.org/wiki/lib/exe/fetch.php?cache=cache&media=bcd:ccr23hearingbds.pdf

The CCR#23 proposed to modify the BDS to a single IR 14mrad 
configuration with push-pull arrangement for two complementary 
detectors. The CCR also specifies the details of the optics and layout; 
in particular, the BDS optics will be compatible to 1TeV upgrade in 
the same layout. Savings from the suggested change amounts to 
approximately one third of the BDS construction cost.

The summary CCB response is as follows -

1. CCB agrees that the cost impact of this CCR (change configuration 
   request), as described by the requesters, is substantial and it 
   qualifies as Class-2. Consequently, CCB assumes that its role with 
   respect to this CCR is to make recommendation to EC (GDE Executive 
   Committee) rather than to make a decision.
2. CCB recommends EC, on the basis of its review as detailed in the 
   "Discussion" section of its full report, to accept CCR#23, whereby
   incorporating the "1IR with two detectors push-pull" as Baseline 
   Configuration.
3. CCB recommends EC to maintain the previous Baseline with "2IR, 
   single hall, two detectors" as part of Alternative Configuration.
4. CCB recommends EC to reinforce a taskforce on Machine-Detector-Interface 
   issues. The taskforce should be specifically charged, and be recognized 
   as such, by both the GDE and WWS, to facilitate pertinent design 
   development efforts and discussions on relevant executive matters.

Additional communication and reference materials are available for
viewing, under CCR #23, at

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

CCB will update the BDS section and the all-in-one file of BCD, with 
possible touch-up to the AC part as per 3, upon final decision by EC.

We wish you all happy holidays.

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