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[Ext-GDE-73] RTML changer request - October 24, 2006 (CCR#19)



Dear Colleagues,

I am announcing that CCB has received a change request proposal
for the RTML section from P.Tenenbaum who is representing the RTML
AG.

This change request contains two ingredients:

- Revision of beamline definitions and functionality descriptions
  of RTML to match the so-called "centralized damping ring
  layout" as proposed with CCR#18, which is currently under
  CCB review.

- Revision of technical implementation of RTML beamlines
  in response to request by ILC management for reducing the
  construction cost of RTML.

The CCB is taking the following actions.

1. Since part of this change proposal is contingent upon approval of 
   CCR #18, which is currently under CCB review, this CCR #19
   is put "on hold". As soon as processing of CCR #18 is completed,
   the CCB will initiate its formal review process.
2. The requester is unspecific about the magnitude of
   cost implications associated with this change proposal. The CCB
   tentatively assigns Class-1 to it. And the CCB reviewers for this
   change proposal will be D.Schulte and K.Kubo, pending
   confirmation.

Although the formal CCB review process will not begin immediately,
the CCB would like to encourage contributions of comments, remarks,
questions by any members of GDE and GDE-related task groups.

Thank you, as usual, for your attention on these matters.

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
RDR wiki for RTML is available at
   http://www.linearcollider.org/wiki/doku.php?id=rdr:rdr_as:rtml_home
   http://www.linearcollider.org/wiki/doku.php?id=rdr:rdr_as:rtml_changes_for_valencia

Sincerely,

- Nobu Toge (KEK, Accelerator Lab)
  email: toge@xxxxxxxxxxxx
  voice: +81-29-864-5224
  fax:   +81-29-864-3182
--- Begin Message --- I am writing to request a change to the baseline design of the Ring to Main Linac (RTML) area of the International Linear Collider. My estimation is that the change in question is Class 2, in excess of M$ 100.

SUMMARY OF CHANGES:

The attached Word file actually contains two sets of changes. One set of changes is the changes which are necessary to make the RTML section consistent with the Overall Layout section, assuming that the recent Change Request for a central DR complex is approved. The other set of changes are those needed to reduce the cost of the RTML by 20% compared to the Vancouver roll-up (excluding the changes needed for the Central DR change, which will of course increase the cost of the overall system while decreasing the cost of the ILC as a whole). In the event that the requested change to the overall layout is rejected, the RTML AS leaders will happily substitute a version of the RTML BCD which contains ONLY the cost-savings changes.

REPLACEMENT TEXT:

Please see the attached Word file.

DESCRIPTIONS:

*Central DR changes:* In order to support the Central DR, the request specifies the requirements for the new beamline that runs from the Central DR complex to the turnaround. In addition to long FODO and FBDB lattices needed to perform the basic transport and geometry matching, the new beamline contains an additional SKEW, COLL, and EMIT sections near the DR and an additional pulsed dump which is used when the bunch compressor, linac, or other systems downstream are unready for beam or in access. Since the exact lengths and geometries of the new complex are not yet determined, the system lengths and component counts related to this part of the change are somewhat approximate, but the numbers are probably good to about 10%.

*Cost Savings Changes:* Upon request by ILC Management, we have identified a number of changes which will reduce the cost of the RTML. The most significant of these are:
   * elimination of 3 RF units in BC2, which reduces the operational
     flexibility of the BC
   * elimination of 3 crab cavities and their supporting RF stations
     per side, which reduces the diagnostic capabilities of the RTML
   * elimination of 2 laser wires (out of 6) in the EMIT station
     downstream of the SPIN section, which eliminates the ability to
     directly measure the normal-mode emittances and coupling terms,
     but preserves the capability to measure the projected emittances
   * Elimination of x correctors at vertically focusing quads
   * Doubling the length of the FODO cell in the turnaround and
     increasing the phase advance per cell, which reduces the number of
     quads, correctors, and BPMs but also increases the emittance
     growth from SR, the momentum compaction, and (possibly) the
     emittance growth from misalignments.

*Impact of Changes:* As discussed in the Central DR change request, we believe that adding the long transfer lines needed for the Central DR will cause an incremental increase in emittance growth, beam-scattering backgrounds, and beam jitter, all of which should be easily managable and are justified by the reduced total cost of the ILC. Plus, if we ever actually upgraded to 1 TeV CM, we would need to face those problems at that time anyway!

The cost savings changes will have an impact on performance, mainly through the reduced flexibility of the compressor and the increased SR emittance growth in the turnaround. We believe that the performance goals of the ILC should still be achievable, but with less margin for error than was originally included in the design.

*Supporting Materials:* There is a detailed wiki page on the proposed changes:

http://www.linearcollider.org/wiki/doku.php?id=rdr:rdr_as:rtml_changes_for_valencia

Note that this page also includes changes to design details which are not under change control at this time (such as the vacuum specification, the positioning and number of access shafts, etc).

*Contact Information:* The person to bother about this is Peter Tenenbaum (PT), quarkpt@xxxxxxxxxxxxxxxxxx

Thank you for your attention.

-PT

Attachment: rtml.23oct2006.proposed.doc
Description: MS-Word document


--- End Message ---