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[Ext-GDE-72] Layout Change Config request - Oct.7, 2006



Dear Colleagues,

I am announcing that today (October 7, 2006) the CCB has received 
a change request for the Parameter and Layout section of BCD from 
Ewan Paterson, the Integration Scientist for the RDR Management.

This change request seeks to redefine the ILC layout in which both 
the electron and positron damping rings are to be relocated in 
a single common tunnel situated centrally around the IR. 

While the fundamental designs of the electron source, positron
source, damping rings and bunch compressors are maintained "as they
have been", the so-called "positron insert" is proposed to be 
eliminated, 400MeV low energy e+ transport mostly eliminated (immediately
boosted to 5GeV), the RTML beam transport lines for both e- and e+ now
extending from the DRs (around IR) over 12km along the ML towards 
the entrance of the bunch compressors near the ML upstream ends.

The main aim of this change request is to slash the construction cost
of the ILC by eliminating the need for civil construction for one of
the tunnel housing and consolidate the facilities for the DRs, although 
some additional beamline elements (RTML) will have to be introduced.

The requester suggested Class 2 as the classification for this change
request. The CCB chair tentatively agrees to treat this as Class 2,
pending more understanding of the associated cost-delta and impacts.

According to the protocol for Class-2 change requests, I am doing
the following.

- I am assigning D.Schulte, S.Mishra, K.Kubo (all to be confirmed), 
  plus myself, to act as CCB co-reviewers.
- I will be:
  * Holding a "review-mode" hearing session concerning the
    cost impacts of the change request, in the presence of 
    GDE Cost Engineers.
  * Sending written inquiries, if any, to relevant AG leaders
    for e- source, e+ source, DR, RTML and ML sections.
- A CCB recommendation report will be drafted within hopefully at most
  approximately three weeks, and will be sent to EC (with cc: to the 
  entire GDE) for their final decision.

Now this request is brought to review by the CCB, and is also open to
general discussion. Any members of GDE or GDE-related task groups with
comments or questions on this request, please, direct them to
ml-ccb@xxxxxxxxxxxx and/or ml-ext-gde@xxxxxxxxxxxx by the end of
Friday, October 13, PDT. 

I also urge the recipients of this notice to share the information
and discussion of this change request with non-GDE members within
the community, and kindly bring feedbacks to CCB and the requester.

My thanks in advance for your cooperation and understanding.

BCD is available at
   http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_home
BCD change history is available at
   http://www.linearcollider.org/wiki/doku.php?id=bcd:bcd_history

Sincerely,

- Nobu Toge (KEK, Accelerator Lab)
  email: toge@xxxxxxxxxxxx
  voice: +81-29-864-5224
  fax:   +81-29-864-3182
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Friends,
          On behalf of the RDR management, the Integration Scientist (jmp@xxxxxxxxxxxxxxxxx) submits the following change request to the Change Control Board. I am copying the affected area and technical syatems at the same time to hopefully avoid any confusion with changes in ILC parameters coming from the many ongoing studies.
                                                                                         Ewan


        CHANGE REQUEST           CHANGE OF LAYOUT of the ILC ACCELERATOR COMPLEX
                                                 Section 1.2

SUMMARY      The recent changes to the Damping Ring parameters, from two to one positron ring, allows the possibility of
             having a single damping ring complex with one tunnel containing both the electron and positron rings. This
             single tunnel system can then be positioned at the center of the ILC layout along with both the electron and
             positron injectors. This Central INJ/DR Complex is illustrated in the schematic in attachment (1).
               A single tunnel housing containing an electron and positron damping is positioned centrally around the IR.
             The electron injector moves 'as is' to the position shown next to the rings on the positron linac side. The
             positron production system is unchanged and the 400 MeV e+ are accelerated to 5 Gev in the usual booster
             which is now next the rings on the electron linac side. The 'Keep alive e+ source' shares the booster as
             before in the same location. The RTML's for both e+ and e- now extend from the central rings to the beginning
             of their respective linacs and these 5 GeV low emittance transport lines are now 12 km longer than before.
             The beam dynamics issues and costs associated with these RTML changes have been analysed by P.Tenebaum (see
             below). There is no longer a positron bypass line around the IR and down the e+ linac and the 1.2 km
             insert in that linac for timing corrections and the KAS have been removed.
               Although the extended RTML lines are more expensive than in the previous layout, the reduction in costs of
             the overall conventional facilities (dominated by the removal of one complete damping ring complex) is 
             considerable and qualifies this change as Category 2. 

TEXT for Section 1.2       Draft Text for layout section of BCD is attachment (2)

DISCUSSION    This is not a final optimization of the central INJ/DR complex as there are several possibilities for
              further cost reductions through the sharing of facilities such as shafts and support tunnels. It was however
              recommended that this request be made at this time because these future changes will have to be an iterative
              process dependent on the acceptance of the "Conceptual Central Injector and Damping Ring Complex"
                The e+/- timing issue has not been ignored in this layout, just put on hold until the many changes under
              discussion which affect the length of various subsystems are stabilized. In the worst case where one might
              still have to adopt a pathlength insert in the linac or RTML, the cost does not change the arguments in 
              favour of the central complex.
                 When and if there is a request for detail cost information, this will be provided by the cost engineers.
              These will be firmed up at the meeting in Caltech next week.
                 There are really only two areas where there is a technical change brought about by this change of layout.
               This biggest is the RTML changes which have been looked at by P.T. See attachment (3)
               The second is the injection and extraction into and from the damping rings. Here there is a lot of
               flexibility and the geometry of the lines may change to optimize other options but there are no required 
               changes in the optics of the rings in any options under study.
                 The present concept has the injectors and damping rings on a plane approimately 10 m above the BDS. This 
               is to allow them to be radiologically separate and to allow operation of this complex on its own while 
               other areas are open or even under construction. This may allow earlier commissioning than with other
               layouts, however the whole construcion schedule, including optimization of cost and schedule) is under 
               study and review. So far the CF&S experts see NO negative impacts from this change in layout, only
               positive, but it is too early to give actual numbers.
                 I have added two more schematics to assist in giving a real scale the BDS, Central INJ/DR, and Linacs.
                 
                

Attachment: ILC_RDR_Scheme_centerDRs.pdf
Description: ILC_RDR_Scheme_centerDRs.pdf

Attachment: Change Control Request Oct 6,2006.doc
Description: Change Control Request Oct 6,2006.doc

Attachment: RTML.ppt
Description: RTML.ppt

Attachment: 3D Image.pdf
Description: 3D Image.pdf

Attachment: Draft layout Schematic.pdf
Description: Draft layout Schematic.pdf


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